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University of Calgary Thesis - Paton Dale
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UNIVERSITY OF CALGARY
Connectivity of Elk Migration in Southwestern Alberta
by
Dale G. Paton
A THESIS
SUBMITTED TO THE FACULTY OF GRADUATE STUDIES
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE
DEGREE OF MASTER OF SCIENCE
INTERDISCIPLINARY GRADUATE PROGRAM
CALGARY, ALBERTA
December, 2012
© Dale G. Paton 2012
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ABSTRACT
The purpose of this study was to investigate the migration of a partially migratory population of
650 Rocky Mountain elk (Cervus elaphus) in the human dominated landscape of southwestern
Alberta. I contribute previously unknown values for metrics known to be important for elk
ecology and management, including: migration timing, distance, and duration . The Brownian
bridge movement model was used to delineate a probabilistic estimate of elk migration corridors
between seasonal ranges, to determine if elk use stopovers during migration and prioritize
migration corridors. Elk used a number of stopovers during migration likely to maximize areas
of rich forage due to spring green-up. Stopovers were found to be >500m from roads in areas of
rugged terrain These stopover locations are critical components in altitudinal migration. Finally
a predictive modeling process using graph theory methods (least cost and circuit theory) was
undertaken to predict connectivity of the landscape for elk.
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ACKNOWLEDGEMENTS
Most importantly, I would like to thank my wife, Karen and daughters Carley, Mollie and
Kestrel for the great support you provided me fo r the duration of my degree. Without your
backing during my preoccupation with this proj ect, completion would have been logistically
difficult. To my wonderful daughter s, the best moment of the enti re thesis process was stalking
elk with all three of you while checking for colla red elk. We were so close and the elk were
totally unaware of our presence. It was great f un. I appreciate the guidance from my supervisor
Mike Quinn who steered me in the right directi on when I needed it the most and understood the
struggles of working and writing a thesis. My graduate committee consisted of Luigi Morgantini,
Greg McDermid and Ralph Cartar. Thank you all for your constructive suggestions to make the
thesis a stronger piece of work.
Numerous people have provided help and guida nce. Angela Braun (SRD) and Tyler Muhly
provided excellent GIS support. Simoe Ciuti a nd Andrew Paul (SRD) guided me through the
statistical relms of R. Hall Sawyer provided the BBMM script for modelling elk migration and
support to initial start-up questions. Once agai n Andrew Paul provided R scripting skills to
expedite analysis of 140 elk migration events in the BBMM. Greg Hale, Travis Ripley, Perry
Abramenko, Kirk Olchoway, John Clarke, Andrew Gustavson, Terry Mack, Brian Sunberg and
Mike Tieghe facilitated logistics for elk capture s. My project received tremendous support from
the Montane Elk Project group particularly th e project manager Roger Creasy, who guided us
through the complexities of a large research proj ect. Collaborators Marco Musiani, Tyler Muhly,
Rob Watt, Bill Dolan, Mark Boyce, Justin Pitt , Jeremy Banfield, Andrea Moorehouse, Barb
Johnson and Rod Sinclair made up an awesome research team. Thank you, Cathy Shier for
providing critical administrative support during collaring events. Bighorn Helicopters and Clay
Wilson helped us collar more elk than we co uld have using anyone el se. Greg Goodison of
Ascent Helicopters made our searches for finding missing collared elk much more efficient with
his trained ears and eyes. Finally thanks to Pa uline Fisk for keeping me on track with the
administrative requirements of U of Calgary.
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This thesis benefited from the support of the Ma rk Boyce and his lab at the University of
Alberta. In particular Simone Ciuti who was always willing to entertain my questions and engage
in discussion of statistics or analysis methods . Finally I would like to thank my parents for
taking me out into wild places and for encour aging me to pursue my passions. Funding for this
project was provided by the Natural Sciences and Engineering Research Council of Canada,
Alberta Conservation Associati on, Royal Dutch Shell, Safari Club International-Northern
Alberta Chapter, Spray Lakes Sawmill, Albert a Sports Recreation Parks, and Devon. Alberta
Tourism Parks and Recreation and Alberta Sust ainable Resource Development provided in-kind
support.
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TABLE OF CONTENTS
ABSTRACT ................................................................................................................................................................II
ACKNOWLEDGEMENTS ..................................................................................................................................... III
TABLE OF CONTENTS ........................................................................................................................................... V
LIST OF FIGURES ............................................................................................................................................... VIII
LIST OF TABLES .................................................................................................................................................... IX
ABBREVIATIONS ..................................................................................................................................................... X
CHAPTER ONE: INTRODUCTION ...................................................................................................................... 11
PURPOSE AND OBJECTIVES ...................................................................................................................................... 13
THESIS STRUCTURE/CONTENTS ............................................................................................................................... 14
CHAPTER TWO: LITERATURE REVIEW ......................................................................................................... 15
IMPORTANCE OF MIGRATIONS ................................................................................................................................. 15
ROCKY MOUNTAIN ELK ECOLOGY AND LIFE HISTORY ........................................................................................... 16
ELK BEHAVIOR AND FORAGING STRATEGIES .......................................................................................................... 18
ELK BEHAVIOUR AND REPRODUCTIVE SUCCESS ..................................................................................................... 19
MIGRATION OF ELK: INFLUENCES OF BEHAVIOUR, FORAGE AND WEATHER ........................................................... 20
Hypotheses for Migration ............................................................................................................. 20
Elk Migration and Predators ........................................................................................................ 23
ELK MIGRATION, DISTURBANCE AND MANAGEMENT ISSUES .................................................................................. 23
Ecological Effects and Management of Roads ............................................................................. 24
LANDSCAPE CONNECTIVITY .................................................................................................................................... 25
SPATIAL ECOLOGY AND MODELING ........................................................................................................................ 27
Seasonal Range Home Range Estimation ..................................................................................... 27
Resource Selection Function ......................................................................................................... 29
Graph Theory and Resource Selection Function .......................................................................... 31
Step Selection Functions ............................................................................................................... 31
Brownian Bridge Movement Model .............................................................................................. 32
LANDSCAPE CONNECTIVITY ANALYSES ................................................................................................................... 34
Least-Cost Path ............................................................................................................................. 36
Current Flow Analysis .................................................................................................................. 37
CHAPTER THREE: USING BROWNIAN BRIDGE MOVEMENT MODEL TO DEPICT ELK LINKAGE
ZONES IN SW ALBERTA ....................................................................................................................................... 40
ABSTRACT ............................................................................................................................................................... 40
INTRODUCTION ........................................................................................................................................................ 40
SW Alberta Case Study ................................................................................................................. 42
STUDY AREA ........................................................................................................................................................... 44
MATERIALS AND METHODS ..................................................................................................................................... 47
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Capture, Collaring, and Data Collection ..................................................................................... 47
Criteria to Determine Migratory Status of Elk ............................................................................. 47
Elk Migration Data and Characteristics ...................................................................................... 51
Modeling Elk Migration Routes .................................................................................................... 52
Estimating Population Level Migration Routes ............................................................................ 54
RESULTS .................................................................................................................................................................. 56
DISCUSSION ............................................................................................................................................................. 70
Elk mortality in study area ............................................................................................................ 70
Migration Metrics ......................................................................................................................... 71
Population Migration.................................................................................................................... 72
Spring and Fall Population Migration ......................................................................................... 75
Migration Characteristics of Different Sexes ............................................................................... 75
Yearling Male Elk Migration and Dispersal ................................................................................ 77
Impact of Wildlife Land Use Management ................................................................................... 78
CONCLUSION ........................................................................................................................................................... 79
Migration Route Modeling ............................................................................................................ 79
Challenges of Elk Migration ......................................................................................................... 80
Research Issues ............................................................................................................................. 83
Management Recommendations and Future Research................................................................. 84
APPENDIX A - ELK MIGRATION ............................................................................................................................... 86
CHAPTER FOUR: ELK STOP-OVER AREAS .................................................................................................... 91
ABSTRACT ............................................................................................................................................................... 91
INTRODUCTION ........................................................................................................................................................ 91
OBJECTIVES ............................................................................................................................................................. 92
STUDY AREA ........................................................................................................................................................... 93
MATERIALS AND METHODS ..................................................................................................................................... 95
Capture, Collaring, and Data Collection ..................................................................................... 95
Identifying Migratory Elk ............................................................................................................. 95
Variable Selection ......................................................................................................................... 96
RESULTS .................................................................................................................................................................. 99
DISCUSSION ........................................................................................................................................................... 103
Percent Cover of Canopy ............................................................................................................ 105
Terrain Ruggedness .................................................................................................................... 106
Aspect .......................................................................................................................................... 107
Wolf ............................................................................................................................................. 107
CONCLUSION ......................................................................................................................................................... 107
CHAPTER FIVE: CONNECTIVITY OF ELK MIGRATION PATHWAYS IN SW ALBERTA .................. 109
ABSTRACT ............................................................................................................................................................. 109
INTRODUCTION ...................................................................................................................................................... 109
STUDY AREA ......................................................................................................................................................... 111
MATERIALS AND METHODS ................................................................................................................................... 114
Capture, Collaring, and Data Collection ................................................................................... 114
Network Models .......................................................................................................................... 114
Data Analysis .............................................................................................................................. 115
RESULTS ................................................................................................................................................................ 117
DISCUSSION ........................................................................................................................................................... 118
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Castle-Carbondale Elk Migration Pathway Connectivity .......................................................... 120
CONCLUSION ......................................................................................................................................................... 126
CHAPTER SIX: KEY RESULTS, MANAGEMENT RECOMMENDATIONS, AND FUTURE RESEARCH
................................................................................................................................................................................... 127
INTRODUCTION ...................................................................................................................................................... 127
RESEARCH FINDINGS ............................................................................................................................................. 128
Migration Pathways .................................................................................................................... 128
Stopover Ecology ........................................................................................................................ 129
LANDSCAPE CONNECTIVITY FOR SW ALBERTA ELK ............................................................................................. 130
Landscape Connectivity for the Castle-Carbondale Elk Subpopulation .................................... 130
MANAGEMENT RECOMMENDATIONS ..................................................................................................................... 130
FUTURE RESEARCH .............................................................................................................................. ................. 131
LITERATURE CITED ........................................................................................................................................... 134
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LIST OF FIGURES
Figure 3-1 Study Area for Castle-Carbondale Elk, 2007 – 2010 (location 694298 E 5483627 N)
....................................................................................................................................................... 46
Figure 3-2 Methods used to determine separate resident elk, migrating elk and dispersing elk
phenotypes using seasonal home range analyses (Boyce 1991) ................................................... 51
Figure 3-3 Example of an utilization distribution estimated for individual elk during the 2008
spring migration............................................................................................................................ 53
Figure 3-4 BBMM of population migration routes of all male and female Castle-Carbondale elk
from 2007-10 ................................................................................................................................. 61
Figure 3-5 BBMM Carbondale-Castle female elk population of spring migration routes and
stopovers, 2007-2010 .................................................................................................................... 62
Figure 3-6 BBMM Carbondale-Castle female elk population of fall migration routes and
stopovers, 2007-2010 .................................................................................................................... 63
Figure 3-7 Comparison of BBMM Carbondale-Castle female elk population stopovers during
spring and fall migration, 2007-2010 ........................................................................................... 64
Figure 3-8 Comparison of BBMM Carbondale-Castle female/male elk population stopovers
during spring migration, 2007-2010 ............................................................................................ 65
Figure 3-9 Castle-Carbondale elk migration is SW Alberta prioritization of migration pathways
determined using proportional use of the collared population (>10%). ...................................... 66
Figure 3-9a BBMM Carbondale-Castle female elk population of spring migration routes and
stopovers, 2007-2010 .................................................................................................................... 68
Figure 3-10 Castle-Carbondale elk using different spring and fall migration pathways ............ 69
Figure A-9 BBMM population utilization distributions for combined fall male and female elk,
2007-2010 ..................................................................................................................................... 86
Figure A-10 Spring utilization distribution of all elk migrations from 2007-2010 ...................... 87
Figure A-11 Fall population utilization distribution of all male elk migrations from 2007-2010
....................................................................................................................................................... 88
Figure A-12 Spring utilization distribution of male elk migrations from 2007-2010.................. 89
Figure A-13 Fall utilization distribution of male elk migrations from 2007-2010 ...................... 90
Figure 4-1 Study area for Castle-Carbondale elk, 2007 – 2010. (location 694298 E 5483627 N)
....................................................................................................................................................... 94
Figure 5-1 Study area for Castle-Carbondale elk, 2007 – 2010 (location 694298 E 5483627 N)
..................................................................................................................................................... 113
Figure 5-2 Network Modeling Framework ................................................................................. 115
Figure 5-3 Graph analysis of habitat connectivity for an elk population of SW Alberta using two
linkage mapping methods based on shortest path ...................................................................... 126
Figure 5-5 A local scale graph analysis of habitat connectivity for the Castle-Carbondale herd
from the Alberta population of elk using the current flow technique ......................................... 124
Figure 5-6 A local scale graph analysis of habitat connectivity for the Castle-Carbondale herd
from the Alberta population of elk using the shortest path and current flow techniques ........... 125
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LIST OF TABLES
Table 3-1 Collared elk from the Carbondale-Castle herd 2007 – 2010 ....................................... 48
Table 3-1 Total number of elk mortalities (n = 21) and the mortality sources for the Castle-
Carbondale herd, 2007-2010 ........................................................................................................ 57
Table 3-2 Migration metrics for Castle-Carbondale elk from 2007 – 2010 ................................. 58
Table 3-3 Characteristics of elk migration for movements and stopovers from 2007 – 2010 ..... 59
Table 4-1 Variables used in the spring and fall elk migration models with predicted effects of
variables ........................................................................................................................................ 98
Table 4-2 Spring Migration AIC Candidate RSF Model Rankings ............................................. 99
Table 4-3 Fall migration AIC candidate RSF model rankings .................................................. 100
Table 4-3 Best Spring Female Elk Migration Model ................................................................. 101
Table 4-4 Best Fall Female Elk Migration Model ..................................................................... 101
Table 4-5 Spring stopovers characteristics of the Castle – Carbondale migratory elk, 2007 -
2010............................................................................................................................................. 102
Table 4-6 Fall stopover characteristics of the Castle – Carbondale migratory elk, 2007 -2010
..................................................................................................................................................... 102
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ABBREVIATIONS
AIC ....................................................................................... Akaike’s Information Criterion
BBMM ........................................................................... Brownian bridge movement model
BMV ...........................................................................................Brownian-motion variance
CAT.......................................................................................... connectivity analysis toolkit
CRW .............................................................................................. correlated random walks
FSH ............................................................................................ forage-selection hypothesis
GIS ...................................................................................... Geographic information system
GPS ............................................................................................. Global Positioning System
Hr ................................................................................................................................... hour
Km.......................................................................................................................... kilometre
m .................................................................................................................................. metre
MCP ........................................................................................... Minimum Convex Polygon
NGO ....................................................................................... non-government organization
RSF ........................................................................................... resource selection functions
RSH ................................................................................... reproductive-strategy hypothesis
SSF ..................................................................................................... step selection function
SW..........................................................................................................................southwest
UD’s ................................................................................................. utilization distributions
UTM ....................................................... Universal Transverse Mercator coordinate system
VHF....................................................................................................... very high frequency
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CHAPTER ONE: INTRODUCTION
Migration is an amazing phenomenon where wild animals travel from one seasonal range to
another over long or short distances, then back to the original range (Berger 2004, Boyce 1991).
Each seasonal movement is timed to follow the food and water resources necessary to maximize
the basic requirements of survival in a historic pattern of moving across the land (Hedenstrom
2003, Holdo et al. 2009). Animal migration is a complex behaviour governed partly by genetics
and population dynamics (Bolger et al. 2007). Critical characteristics of migration include
navigation, timing of migration, site fidelity, social behaviour and morphological and
physiological adaptations (Bolger et al. 2007). Migration has both costs and benefits for animals
and defining these trade-offs are difficult (Bolger et al. 2007, Hebblewhite and Merrill 2009).
There is a growing interest in why populations of migratory animals are declining globally
(Wilcox 2007), with conservationists noting the importance of protecting migration corridors and
dispersal of wildlife (Schaller 1988. Berger 2010).
Grazing by herbivores has a significant effect on ecosystems and a good understanding of
migration is necessary to understand their functional role in ecosystems (Mysterud et al. 2012).
Besides their economic and social value to humans, animal migrations cycle nutrients and
facilitate additional ecological process. Migration promotes ecosystem resilience that enhances
the ability of natural systems to recover from disturbances and stresses, including manifestations
of climate change (Walther et al. 2002). The ecology of ungulates in the Rocky Mountains is
strongly influenced by climate. Climate change affects summer precipitation, winter snow pack,
and the timing of spring green-up, all of which control animal physiology, demography, diet,
habitat selection and predator prey interactions. Migration is an important component of elk
survival strategies. Similar to other herbivore species, elk migrate to higher elevations in the
spring, due to retreating snow cover and greater food availability and return to winter range in
the fall.
Maintaining elk populations provides ecological, social and economic benefits. Wildlife viewing
and hunting generate millions of dollars to local economies. Elk can contribute to maintaining
early successional habitat conditions which have declined over the past several decades due to
influences such as fire suppression. Elk generate some concerns due to the potential for damage,
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nuisance activity, and disease transmission. Agricultural damage is most common with elk
foraging on and trampling crops, damage to fences and competition with livestock for forage
(Hegel et al.2009). Other types of damage caused by elk include over-browsing of timber
resources, vehicle collisions, nuisances and safety concerns due to habituation to humans.
Many causes for loss or decline of migration events arise from human influences that increase
fragmentation, disturbance, deteriorate habitat quality and result in a loss of habitat connectivity
(Berger 2004, Berger et al. 2006, Leu et al. 2008, Naylor et al. 2009, Sawyer et al.
2009).Although all the implications for disruption of migration are not well known, migration is
important to the continuation of large, mobile ungulate populations (Bier and Noss 1998, Epps
et al. 2005) and to predators that use elk as a food resource (Hebblewhite et al. 2006,
Moorehouse 2010, Moorehouse and Boyce 2011, Nelson et al. 2012). Employing our growing
knowledge of elk migration and movement patterns in management decisions is needed, even
though it will be complicated because landscape management must also consider ecological,
biophysical and social-economic processes important to other species besides elk (Bennet et al.
2011). Finally, conservation of migratory species requires identifying and mapping migratory
routes (Thirgood et al. 2004, Sawyer et al. 2009, Strandberg et al. 2009) as well as understanding
the role of individuals and environmental influences on migratory patterns (Alerstam 2006 and
Bolger et al. 2008). My thesis provides new insights into the conservation of the migratory
Castle-Carbondale elk herd by determining migration routes and associated metrics.
In southwestern Alberta the elk population is approximately 4,300 animals, separated into seven
subpopulations, each having wintering and summering areas (Clark 1993, Jorgensen and Kansas
1992, Morgantini 1994). Five of the 7 herds are considered partially migratory based on their
annual movements during the time period of my study (2007 – 2010). I chose to study the
partially migratory Castle-Carbondale subpopulation because it had the highest sample size of
collared elk. Secondly the home range of the herd is an area exposed to concentrated human
activity from a wide variety of recreation and resource extraction activities (Muhly 2010,
Northrup 2010). Finally, few elk migration studies have been conducted in areas with such a
high influence of human activity from numerous sources. Quantitative data of elk migration are
expected to be particularly important in this region due to this degree and types of human activity
occurring on the landscape. Collared female elk were adults and juveniles, whereas only yearling
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males were collared. Yearling males were collared to provide potential dispersal data and there
were concerns within the study group that collaring of mature male elk could be detrimental to
the elk during the rutting period when neck swelling occurs. It was possible the collar could
become too tight on the neck resulting in negative consequences for the elk. The sampling
regime intensity for elk in the Carbondale-Castle elk was comprised of 39 female elk and 14
male elk with their collars scheduled to collect GPS relocation fixes every 2 hours, 24-hours a
day for a time period of 2 years, beginning in 2007 (Table 2-1). The age of elk varied from 1
year to 18 years.
If the dynamics of elk migration continue to be poorly understood, elk migratory behaviour
could change, halt or become reduced in scope. It may result in more animals remaining on their
winter range, creating new or increasing existing negative elk / human interactions and /or
ecological damage such as overgrazing grasslands or crop damage (Hebblewhite et al. 2006, Ito
et al. 2005). The population size could also be significantly reduced if migration were
discontinued causing a shortage of food resources from too many elk on too small of a home
range, resulting in over-use of some resources and changing ecological processes and loss of
biodiversity through cascading effects (Ripple et al. 2001, Hebblewhite et al. 2006, Romme et al.
2011). High herbivore densities are also known to have negative impacts on plant communities,
resulting in a reduction in biodiversity (Hebbblewhite et al. 2005). For these reasons,
management agencies and resource extraction industries should be aware of the potential effects
of human disturbance to migratory elk and take efforts to reduce disturbance.
P
URPOSE AND OBJECTIVES
I studied the partially migratory Castle-Carbondale subpopulation comprised of approximately
650 elk (Clark 1993). I sought to delineate the migration route or routes used by Castle-
Carbondale elk. The elk migrate up to 34 km straight line distance from their winter range, a
montane / agricultural landscape to high elevation summer range on the Continental Divide in
Alberta Canada. I hypothesized that:
Elk would migrate along specific pathways each year without stopping over because the
migration distance is relatively short, traversable by elk in a day or two.
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Fall migration would differ from the spring migration corridor.
From the potential results of my hypotheses testing I developed three objectives;
If stopovers were used by elk, I would investigate their characteristics;
Male and female seasonal migration stopovers would spatially differ, possibly from
sexual segregation.
If elk migrated on specific routes, I would use graph theory methods to assess the
connectivity of the migration pathways of elk at local and regional scales.
Modeling and statistical analysis of elk global positioning systems (GPS) location point data
were used to develop and support conservation planning for partially migratory elk herds in
southwest Alberta. My program of study at the University of Calgary was interdisciplinary in
nature providing an opportunity to combine resource management and research into my thesis. I
have chosen to incorporate three disciplines: Biological Sciences, Geography and Resource
Management into the design and implementation of my study.
THESIS STRUCTURE/CONTENTS
In Chapter Two I present a literature review of elk ecology, effects of human activity to wildlife,
and applicable spatial ecology analysis techniques useful to this study. I identified methods to
determine elk migratory phenotypes, spatial and geospatial ecology techniques to depict and
understand migration route characteristics and investigate landscape connectivity for migration.
In Chapter Three I use the BBMM as an analytical framework (Sawyer et al. 2009) to identify:
1) a system of migration pathways and connected stopover sites for elk, and 2) prioritize
population migration pathways based on their proportional degrees of use for 50 elk. My goal in
Chapter Four was to use resource selection functions (RSF) to identify characteristics of
stopovers by comparing used elk relocation points to randomly selected location points in the
Castle-Carbondale elk home range. Chapter Five uses graph theory methods of least-cost path
and/or current flow methods to investigate connectivity of elk migration routes for the Castle-
Carbondale herd (local scale) as well as a regional scale analysis. In Chapter Six I use results of
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all the thesis chapters to provide possible management strategies for conservation of migratory
elk in southwest Alberta.
CHAPTER TWO: LITERATURE REVIEW
I present a literature re view of elk ecology, effects of human activity to wildlife, and applicable
options of spatial ecology anal ysis techniques useful to st udy elk migration. Methods are
assessed to determine elk migratory phenotypes, spatial and geospatial ecology techniques to
depict and understand migrati on route characteristics and inves tigate landscape connectivity for
migration.
I
MPORTANCE OF MIGRATIONS
Typically, migrating cervids in the temperate region select high elevation summer range and a
low elevation winter range (Fryzell and Sinclair 1988, Sawyer et al. 2009). A downhill
migration in fall to winter range is a response to weather conditions and a strategy to find
wintering areas with shallow snow depth (Boyce 1991, White et al. 2010). Large herbivore
migrations are universally considered vulnerable to human development (Berger 2004, Sawyer et
al. 2009). The ability of animals to migrate is vital for the viability and maintenance of migrating
populations. Halting or reducing migrations may result in a population decline of ungulates that
can be amplified by additional disturbance events or increased predation pressure (Coulon et al.
2006, Hebblewhite et al. 2006, Harris et al. 2009, Voeten et al. 2009). When migratory
ungulates are confined to one range, negative density-dependent effects may occur. This
restriction to a single range can lead to reduced forage availability and quality (Christianson and
Creel 2009). The highest quality forage is readily removed by dominant individuals or efficient
foragers, leaving a more homogenous and less nutritious diet for other herd members (Mysterud
et al. 2001, Nicholson et al. 2006). A lack of adequate nutrition will lead to reduced fertility and
calf survival (Cook et al. 2004). Overgrazing by ungulates can negatively impact ecological
processes, reducing grassland productivity, riparian area conditions, water quality and
biodiversity (Frank and Goffman 1998, Stewart et al. 2009, Ripple et al. 2001, Romme et al.
2011).
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Migration events are an ecological necessity for the existence of wide ranging populations and
meta-populations, often essential to the genetics of these populations (Soule 1991, Coulon et al.
2006) and allow increased access to resources and habitat (Saher and Schmiegelow 2004). In
some cases bottlenecks have developed in migration routes threatening future movement of
species along the migration corridor (Williamson et al. 1988, Mahoney and Schaefer 2002, Ito et
al. 2005, Berger et al. 2008). Maintaining connectivity between calving grounds, summer ranges
and wintering grounds is expected to be important if not essential to migrating elk fitness and
populations.
Much of the migration literature focuses on the event and process of migration; fewer efforts are
dedicated to the ecological benefits of wide ranging grazers to ecosystems (Augustine and
McNaughton 1998, Frank and Goffman 1998) or to the knowledge we could gain from studying
functioning migration routes to advance corridor or linkage ecology (Chetkiewicz et al. 2006).
Migratory ungulates serve an important stabilizing function on ecosystems by their grazing
pressure on plants (Kie and Lehmkuhl 2001). Halting of migration can have destabilization
effects on vegetative communities and species interaction (Kie and Lehmkuhl 2001) causing
significant reductions in biodiversity (Manier and Hobbs 2007). Finally, effects of human-
related disturbances on wildlife energetics, demography and habitat selection is particularly
important among temperate ungulates whose survival depends on minimizing energy
expenditures during winter (Hobbs 1989, Sawyer et al. 2006, Parker et al. 2009). Land and
wildlife managers require information of migration timing, characteristics and corridor or travel
routes used to incorporate into conservation of migrating animal populations and pathways.
Once the migration corridors are known the reasons why elk use these areas can be explored and
alternatives for management can be developed. Not only is this important for current elk
management practices but for future management of numerous species, for maintaining
connectivity of migration corridors and as a strategy to provide options for animals to adapt to
changing climate (Soule et al. 2003, Minor and Urban 2008).
ROCKY MOUNTAIN ELK ECOLOGY AND LIFE HISTORY
Of the North American ungulates, elk are one of the most widely-distributed and frequently
studied species. As a very common species they capture the curiosity of people due to their
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tendency to be observed in impressively large herds, their regal stature as they alertly respond to
human presence, and their apparent ability to adjust to human activity. These qualities are
intertwined with their response to human disturbance, their selection of ecotone environments,
topographic features such as slope, elevation, aspect and predation risk are also recognized to
influence elk habitat selection patterns (Edge et al. 1987, Skovlin et al. 2004). Results of recent
elk research are predominantly reporting elk avoidance responses to disturbance from human
activity and resource development (Van dyke et al. 1997, Rowland et al. 2000, Frair et al. 2008,
Hebblewhite and Merrill 2009, Naylor et al. 2009, Sawyer et al. 2009) potentially affecting their
fitness and distribution. To a lesser degree, this response to human activity is true in areas of no
hunting such as private lands and legislated protected areas (Rogala et al. 2011).
As an ecotone species, elk prefer a mosaic of forests and open grasslands providing security
cover from predators and human disturbance, while corridors or secluded landscapes provide
travel routes or security between seasonal habitats (Naylor et al. 2009). Travel corridors are
essential for elk by providing security during travel or access to the best available habitats. In the
case of elk migration, they may require a pathway with forage and stopover locations to and
from seasonal ranges, similar to migrating deer (Sawyer et al. 2009). This study of Rocky
Mountain elk in southwestern Alberta investigates the phenomenon of elk migration.
The elk population southwestern Alberta is comprised of three phenotypes defined by the
animal’s seasonal distribution on the landscape. These phenotypes are resident, migratory and
disperser (Boyce 1991). Elk with seasonal home ranges overlapping entirely or predominantly
are defined as resident elk. Migratory elk move from a winter range to a separate summer range
and return to the same winter range, whereas dispersing elk will leave the winter range to another
separate seasonal range, not returning to the original wintering area (Boyce 1991). Some elk
populations are partially migratory, where one segment of a population undertakes seasonal
migration and the other remains on a single range year round (Lundberg 1988, Hebblewhite et al.
2006). A majority of the elk population in southwestern Alberta is partially migratory.
To study elk migration and their movement patterns it is beneficial to have an understanding of
what compels elk movement on the landscape over space and time (Willems and Hill 2009).
This section of the literature review outlines relevant information regarding what is known about
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how and why elk respond to landscape features, how they alter their movement in response to
time of day, predator presence, landscape composition, and forage. Human uses of the landscape
such as roads, agriculture, and residential development also affect elk distribution on the land,
possibly reducing elk accessibility to forage and an increase in vigilance (Lung and Childress
2007) which in turn has the potential to reduce fitness (Rowland et al. 2000, Boyce et al. 2010,
Stewart et al. 2010). In other cases human activities may improve elk habitat (Frair et al. 2008,
Rumble and Gamo 2011). To present these concepts, I will describe applicable movement
strategies used by elk to fulfill their life history requirements. The latter chapters provide a
discussion of how these strategies relate to, or are expressed in, elk migration phenotypes and
methods of analyses.
E
LK BEHAVIOR AND FORAGING STRATEGIES
Understanding elk movement involves interpreting elk behaviour, or what motivates elk to move
across the landscape. Patterns of elk activity are known to be circadian cycles between foraging
and secure resting habitats with dawn and dusk shifts (Collins et al. 1978, Irwin and Peek 1983,
Green and Bear 1990, Ager et al. 2003, Boyce et al. 2009). Evolutionary theory provides
insights into a primary goal of elk which would be to optimize the use of available resources to
ensure reproductive success (Geist 2002). Elk are ecological generalists that do not expend
much energy contesting feeding sites with other animals, but respond by moving on to another
area. Theory suggests an animal should remain in an area as long as the marginal rate of forage
intake is greater than the average forage value of the landscape (Charnov 1976), and that
foraging and movement strategies influence energy budgets and fitness (Moen et al. 1997).
Efficient use of energy resources must be balanced with risks of predation (Kie 1999, Brown and
Kotler 2004, Fortin et al. 2005), landscape structure (Crist et al. 1992, With et al. 1994),
processes such as circadian rhythms (Bascompte and Villa 1997, Bergman et al. 2000, Morales
and Ellner 2002) and behavioral states such as resting, foraging and relocating (Morales et al.
2004, Frair et al. 2005).
The distribution of migratory elk in the Rocky Mountains shifts seasonally to areas of available
food supply (Merrill 1994). The winter diet is typically defined by snow conditions (Boyce
1991). Elk survive through the winter on grasses, particularly on wind-blown ridges, and move
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to ranges where snow depths are lowest. If snow depths increase and grass is not accessible, elk
will switch to eating tall shrubs or conifers (Singer 1995). During the spring, elk will begin
grazing on plant species developing new growth such as grasses and in summer increase
consumption of forbs or shrubs. Fall forage for elk includes dried grasses or re-growth of some
grasses such as bunch grasses (Cook 2002, Smallidge et al. 2010). Opportunistically feeding on
rich nutrients and biomass from forage is one of the reasons why elk travel, and this combination
may be related to topographical relief and following an elevation gradient (Morgantini and
Russel 1983, Hebblewhite and Merrill 2008, Hebblewhite and Merrill 2009, Webb et al. 2011).
Weather and topography also interact to affect elk behavioural foraging strategies. For example,
landscape heterogeneity frequently originates from diverse topographic relief that affects the
distribution of soils and microclimatic conditions associated with elevation, aspect, slope and
drainage (Boyce 1991, Hedenstrom 2003). These factors influence local vegetation and affect
patterns of elk habitat use due to food preference and availability. An additional important factor
is elevation due to its relationship with temperature and precipitation, which is directly related to
snow accumulation and plant phenology (Morgantini and Hudson 1989, Singh et al. 2010).
Habitat use by elk may vary with elevation in different seasons. Elk use upper slopes in all
seasons but in winter elk prefer upper south-facing slopes that are free of snow due to the effects
of wind and solar radiation (D’Eon and Serrouya 2005). During summer elk use upper landscape
locations related to cooling winds, visibility and cover type (Nelson and Burnell 1975).
ELK BEHAVIOUR AND REPRODUCTIVE SUCCESS
The goal of all animals is to maximize fitness. Mature male and female elk differ in their
selection of habitat and choice of movement patterns due to different behavioural goals (Geist
1998). An important goal of the female is to guarantee security for her calf. Therefore, female
elk may compromise access to the highest value food sources in a tradeoff to provide security for
its calf in a foraging gain-predation risk trade-off (Geist 1998). Bulls, in contrast, seek out high
quality food over security to provide the nutrients to reach large body and antler size important
for successful breeding. Such differences in emphasis should result in spatial segregation of
females and males (Geist 2002).
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Reproductive success and timing is determined by the availability of nutrient rich food needed
for gestation and lactation. In cold, high latitudes and altitudes, births must happen just before
vegetative green up in early summer, thus providing the female with a high quality food source
to produce rich milk for the calf (Cook et al. 2004). This in turn confines the timing of the rut to
the latter part of September, as gestation takes 250 days with peak calving occurring in early
June during a narrow window of abundant rich forage (Giest 2002). Calves born too early will
suffer from poor milk yield and those born too late may not grow to a size where they are able to
live through the winter (Geist 2002, Cook et al. 2004).
A breeding time period demands incredible energy expenditure by the bulls. This selects for
bulls able to store large amounts of fat to support breeding and carry over after the rut, as the rut
is a time period of reduced feeding and high energy expenditure. To be able to acquire the
excess fat reserves for survival, elk appear to exhibit foraging strategies necessary to acquire an
adequate supply in quality and quantity of food by being driven to high food consumption in the
summer (Geist 2002).
M
IGRATION OF ELK: INFLUENCES OF BEHAVIOUR, FORAGE AND WEATHER
Hypotheses for Migration
Patterns of migration have evolved in animals to take advantage of spatial and temporal
variations in the environment. Selection should favour individuals that migrate if by migration
their reproductive success is enhanced (Fryzell and Sinclair 1988). Reductions of predation risk
and diet enhancement are two common hypotheses for migration (Fryzell and Sinclair 1988).
Theoretical models (Cohen 1967, Fryzell and Sinclair 1988) and the concept of evolutionarily
stable strategies (Parker and Stuart 1976) are used to explain why individuals migrate. A
common denominator of most models is reproductive success, and lifetime reproductive success
is a function of both survivorship and birthrate. The adaptive significance of migration may be
best understood by the forces of selection influencing these life-history parameters (Cohen 1967,
Fryzell and Sinclair 1988). Quality and availability of forage affect survivorship and birthrate,
and so does the risk of predation. Maximizing intake of nutrient rich forage and avoiding
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predation are described as possible factors encouraging migration (Taylor and Taylor 1977,
Albon and Langvatn 1992, Robinson et al. 2010).
Fall migrations for many populations of elk appear to be strongly influenced by snow depth,
plant phenology, elevation, topography, and hunting pressure (Boyce 1991, Irwin 2002, Boyce et
al. 2003, Smith 2007). The main driver causing migration to low elevation in fall is snow (Boyce
1991, Albon and Langvatn 1992, Hebblewhite et al. 2008). The mechanism of migration in
spring is less clear. One important evolutionary influence for migration behavior may involve
the length of time elk can have access to high quality nutrient rich food sources (Morgantini and
Hudson 1989, Boyce 1991). High elevation vegetation on summer ranges is comprised of much
higher nutritional value than food sources at lower elevations (Hebert 1973, Albon and Langvatn
1992) and elk distribution can be predicted on the basis of spring vegetation index values (Singh
et al. 2010, Smallidge et al. 2010). This represents the forage maturation hypothesis which is
commonly used to explain uphill migration in spring (Fryxell and Sinclair 1988) and was tested
for elk and red deer (Hebblewhite et al. 2008, Albon and Langvatn 1992). However, theories
describing the combination of presence of nutritious vegetation and altitudinal migration have
yet to demonstrate increased fitness to migrating elk (see Mysterud et al. 2001).
Predation risk may also be an important function in migration (Hebblewhite and Merrill 2007).
Migration could serve as a means to avoid areas with high predation risk (Edwards 1983, Festa-
Bianchet 1988). The predation risk avoidance hypothesis could be applicable to migration with
animals moving seasonally away from areas of high predation risk.
Another hypothesis, the avoidance of competition hypothesis which suggests that migration
strategy could be controlled by genetics or a density-dependent selection which may result in a
partial migration of a population. This could be conditional where genetics allows for adoption
of a range of migratory behaviours (Fryzell and Sinclair 1988). Partially migratory populations
of elk are found in North America and have been used to investigate if migration has fitness
benefits for elk (Hebblewhite and Merrill 2009). A prediction of the avoidance competition
hypothesis is that populations of partially migratory ungulates may have an increasing proportion
of migrants at higher density (Mysterud et al. 2012).
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Much of the discussion with population density is the lack of a good measure of variation in
habitat quality which is necessary to assess a level of competition (Mysterud et al. 2012).
Density dependence in a segment of migrants may be a good test of competition avoidance
(Mysterud et al 2012). To access the effects of landscape structure on animal distribution one
could investigate elements likely to reflect habitat quality, such as population density, home
range size, and survival with variables such as vegetation structure and animal density using the
ideal free distribution theory as a framework (Stewart and Komers 2012, Thompson and Gese
2012). According to the ideal free distribution, high quality habitat should be occupied to a
certain threshold at which point completion or social structure forces animals into poorer quality
areas (Thompson and Gese 2012).
For many species partial migration is common. It been noted in studies of elk and red deer
(Cervus elaphus) (Woods 1991, Mysterud et al. 2011), moose (Alces alces) (Andersen 1991),
mule deer (Odoicoleus hemionas) (Nicolson et al. 1997), and white-tailed deer (Odocoleus
virginianus) (Forbes and Theberge 1995). Partial migration may be sustained by a demographic
balancing of the two migratory methods (Lundberg 1988). Individual-based animal strategies
may switch between migrant or resident states due to population density or with varying resource
abundance (Lack 1968). Another strategy is to use a state-dependent migrant or resident strategy
based on age or body condition (Adriaensen and Dhondt 1990, PetezpTris and Telleria 2002).
The third possibility is a population level strategy where animals are migrant or resident and
proportions are determined at the population level by density-dependent fitness (Lundberg 1988).
Few studies have found a strong genetic basis for migration in ungulates (see McDevitt et al.
2009). When migration is based on the forage maturation hypothesis or predation risk, partial
migration could be maintained where residents limit possible demographic costs of foregoing
migration, even if a low frequency of residents is sustained in the population (Fryxell et al.
1988). Alternatively, the loss of migration could be expected when residents make risk-forage
tradeoffs to reduce risk and achieve high forage on winter range year round (Hebblewhite and
Merrill 2009). Understanding such dynamics would provide valuable insights into declines in
migratory behaviour.
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Elk Migration and Predators
Elk use a number of strategies to reduce the risk of predation and, in turn, increase survival
(Winnie et al. 2006). In response to predation risk, animals increase vigilance (Lima and Dill
1990), reduce foraging time or movements (Sih and McCarthy 2002), change group size (Creel
and Winnie 2005) and undertake habitat shifts to less risk areas or to refuges (Blumstein and
Daniel 2002, Proffitt et al. 2010). One method to shift habitats to avoid predation is to migrate.
Many North American large predators are unable to undertake long distance movements for prey
during portions of the year because the predators must remain near their den sites to look after
young until they are mobile (Fryzell and Sinclair 1988, Boyce 1991, Creel 2002).
Elk distribution is affected by the trade-offs between the risks of predation and the requirement
to access the most nutritious food sources available (Robinson et al. 2010). In summer, forage is
typically plentiful, resulting in elk having the option to move away from predators with low
consequences to fitness. In contrast, predation threats on the winter ranges where forage is
limited may force elk to be exposed to higher predation risk in favour of forage availability
(Robinson et al. 2010). In other situations elk may stop migrating from winter ranges to summer
range possibly because the winter range has greater security from predators due to the presence
of humans (Hebblewhite 2006). In the case of hunting, elk and other animals adjust to predation
risk by moving into areas of high security such as forest cover, rugged terrain, low road density
areas, low traffic volumes, (Morgantini and Hudson 1985, Unsworth et al. 1998, Dill et al. 2003,
Wright et al. 2006) or lands designated ‘no hunting’ (Vieira et al. 2003, Proffitt et al. 2010).
ELK MIGRATION, DISTURBANCE AND MANAGEMENT ISSUES
Migrating elk provide ecological benefits to the land when they move off winter range to the
summer range allowing vegetation regrowth to occur. This cycle of grazing can work well in a
winter range only used by wild ungulates, but frequently elk home ranges occupy land found in
areas of multiple land-uses (Boyce 1991) where competition for resources can occur. Combined
with the difficulties of elk competing for forage with cattle, elk can cause crop depredation
problems, eating stored hay or grain crops in agricultural fields creating both direct and
perceived conflicts (Hegel 2009). As well as direct competition, overgrazing by wild and
domestic animals of a grassland ecosystem may reduce the viability of the grassland system,
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reducing its productivity for both grassland dependent wildlife and the ranching industry (Frank
and Goffman 1998, Kie and Lehmkuhl 2001). Mitigating or solving wildlife impacts to ranching
activities is challenging. Wildlife damage management is complex because it involves biological,
physical, economic and socio-cultural factors (Slate et al. 1992). Such diverse ranges of issues
are why the increasing use of the land by people and the belief that people rights have priority
over wildlife needs of habitat will continue to make management of wildlife complex (Cherney
and Clark 2009).
Ecological Effects and Management of Roads
One of the most widespread modifications of the natural landscape has been from the
construction and maintenance of roads (Forman 2003). Roads affect ecosystems in several ways,
including: increased wildlife mortality, modification of animal behaviour, changing the physical
environment, reduction of genetic interchange, spread of exotic plant species, and limiting
dispersal of young (Beier 1995, Gerlach and Musolf 2000, Trombulak and Frissell 2000, Epps et
al. 2005, Proctor et al. 2005). Roads with high human use have the potential to modify animal
behaviour by causing animal avoidance of roads, resulting in a reduction in permeability of
landscape (Gibeau et al. 2001, Dodd et al. 2007). Such changes in animal behaviour can result in
future fragmentation or isolation of populations.
There are two main categories to describe the effects of roads on elk: indirect effects on habitat
use and direct effects on individuals and populations. Roads are known to affect forested
ecosystems, and they are the primary cause of wildlife habitat fragmentation (Forman 2003).
Areas with high road density may not have patches of forest cover large enough to be effective
habitat for elk, particularly in hunted populations (Rowland et al. 2004). Direct effects include:
mortality from vehicles, elk avoiding areas near travelled roads, vulnerability to mortality from
legal and illegal activity increases as road density increases. In areas of high road density, elk
demonstrate evidence of higher levels of stress and increased movement rates (Lyon 1979, Rost
and Bailey 1979, Morgantini and Hudson 1979, Wisdom et al. 1986, Frair et al. 2008).
Management strategies that eliminate vehicle traffic on roads can reduce the indirect effects of
roads (Witmer and deCalesta 1985) and could increase survival and reproduction due to reduced
energy expenditure and less vulnerability to hunting (Cole et al. 1997, Shively et al. 2005),
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provided the closure keeps out vehicles. Extensive shifts in elk distribution away from roads are
a wide spread phenomenon, and at a landscape level have the potential to affect elk carrying
capacity and elk distribution (Rost and Bailey 1979, Lyon 1983, Edge and Marcum 1991,
Rowland et. al. 2000, Naylor et al. 2009).
Persistently high levels of disturbance from recreation and human developments on elk home
ranges have the potential to impact ungulate reproductive performance (Yarmoloy and Geist
1988, Joslin and Youmans 1999, Phillips and Alldredge 2000, Wisdom 2007, Stankowich 2008)
and alter migratory movement patterns. Elk will move from areas of high levels of disturbance
to areas of low disturbance (Proffitt et al. 2010). In land management regimes of multi-use such
as SW Alberta the movement of elk to areas of lower human disturbance might result in wildlife
spending more time on private lands where there is low disturbance due to limited public access
in comparison to public land ranges that often have much higher levels of human disturbance
(Joslin and Youmans 1999, Northrup 2010). To find solutions to such issues, it will be necessary
for management agencies to partner together in developing policies to take into account the
needs of people, wildlife and land conservation (Brook 2007). Landscape management to reduce
fragmentation and improve connectivity for wildlife movement is an essential concept to
implement into the wildlife management solution (Carroll et al. 2011).
LANDSCAPE CONNECTIVITY
Connectivity of landscapes is considered to be important to the movement of genes, individuals,
populations and species at a variety of time scales (Minor and Urban 2008). Over a short time
period, connectivity may affect successful juvenile dispersal and limit the possibility of
recolonization of unoccupied patches of habitat. At medium scales of time it may influence the
ability of animals to migrate or persistence of metapopulations and at the longest time periods it
could influence the ability of species to increase or modify their range due to climate change
(Minor and Urban 2008).
Many North American habitats are becoming fragmented with increases of fragmentation
expected to occur due to development and land use. Prugh et al. (2008) proposed fragmentation
to be the greatest threat to most species in the temperate zone and Noss (1991) has stated it is the
one greatest threat to biodiversity. Fragmentation can also restrict animal movements for
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foraging, breeding, migration and dispersal making its effects a global issue for conservation of
flora and fauna (Bennet 2003). As fragmentation of habitat continues, isolation of habitat
patches increases and the need to restore landscape connectivity becomes greater (Noss 1987,
Ogen 2012). Combining potential global changes due to climate change will confound the
effects of fragmentation by reducing ecosystem and habitat resilience. This may further restrict a
species ability to move to suitable habitats in response to climate change (Soule et al. 2003).
Increased habitat fragmentation due to the impacts of climate change could result in socio-
economic impacts for the costs of replacing lost ecosystem services such as water purification
and retention or flood/erosion prevention (Kettunen and ten Brink 2006).
To understand and predict solutions for connectivity, analyses have been developed based on
graph theory methods, euclidean distance and others (Calabrese and Fagan 2004). Graph theory
is commonly used in connectivity theories and corridor delineation methods (Chetkiewicz et al.
2006, Urban et al. 2009). Graphs are a proven method to understand meta-populations and
provide a means to undertake connectivity analyses of landscapes (Urban et al. 2009, Beier et al.
2010). Graph theory seems suitable for determining the connectivity of migratory habitat
(O’Brien et al 2006). In addition the combination of graph theory and RSF models may provide
a means of quantifying connectivity because it combines spatial topography with resource
selection and is particularly useful in scenario testing by predicting the effects of adding or
removing landscape elements (Chetkiewicz et al. 2006).
Scenario-testing is considered a tool for predicting effects of possible future developments and is
a way to forecast what may occur considering long-term consequences of potential land use
decisions. Identification of bottlenecks or sinks provides information of potential areas for
restoration such as removal of active roads which may help to reduce or increase connectivity.
It has been suggested maintenance and restoration of connectivity between patches of high
quality habitat is an important goal for conservation of animal populations (Rayfield et al. 2010).
The increasing awareness of the negative effects of habitat fragmentation on ecological systems
has improved efforts to reduce current fragmentation of natural systems as well as development
of analytical tools required to predict and evaluate the effects of developments to a land base
(Theobald et al. 2006).
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SPATIAL ECOLOGY AND MODELING
A variety of statistical / modeling methodologies have been used to describe and study elk
migratory behaviour (White and Garrot 1990, Felix et al. 2007). Defining migration is a
complex task because migration characteristics vary between species, and individuals within the
species. A number of definitions have been used in research projects with methods to determine
elk migration phenotype. A common defining characteristic of migration is a shift in use of
habitat, although this definition is complicated by different sex and age classes of ungulates
potentially selecting habitats differently (Mysterud 1999, Bowyer and Kie 2006). A basic and
frequently used definition of migration is presented by White and Garrot (1990). They define
migration as a regular, round trip movement by individuals between two or more areas or
seasonal ranges. A variety of methods may be used to define separation of seasonal ranges
including minimum convex polygon (MCP) (White and Garrot 1990, Mysterud 1999), spatial
distributions of median summer locations using complete linkage Euclidian distance (White et al.
2005), cluster analysis (White et al. 2007), and 95% kernel analysis (Felix et al. 2007). No
minimum distance between seasonal ranges has been established as a standard in the definition
of migration.
Seasonal Range Home Range Estimation
Migratory elk can be defined as one of three phenotypes defined by the animal’s seasonal
distribution on the landscape. These phenotypes are: resident, migratory and disperser (Boyce
1991). Elk with seasonal home ranges overlapping entirely or predominantly are defined as
resident elk. Migratory elk move from a winter range to a separate summer range and return to
the same winter range, whereas dispersing elk will leave the winter range to another separate
seasonal range, not returning to the original wintering area (Boyce 1991). Some elk populations
are partially migratory, where one segment of a population undertakes seasonal migration and
the other remains on a single range year round (Lundberg 1988, Hebblewhite et al. 2006). I use
seasonal home range analyses techniques to define each phenotype of elk.
Two frequently used methods of home range estimation are MCP and kernel density estimation.
Kernel density estimates are the most commonly used method to assess and visualize animal
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home ranges (Laver and Kelly 2008, Kie et al. 2010). With this method the most important issue
is choosing an appropriate smoothing parameter (bandwidth). Bandwidth is critical in
determining the outer contours of the home range estimate and it also affects estimation of the
utilization distribution (Seaman and Powell 1996). A tested concession to reduce over-
smoothing is to set the bandwidth at .70 (Bertrand et al. 1996) or .80 (Kie and Boroski 1996, Kie
et al. 2002). Home range analysis is a fundamental methodological concept, with considerable
discussion regarding how it is best measured (Kenward 2001, Kie et al. 2010, White and Garrot
1990). Accuracy of home range estimates is influenced by a number of artifacts of sampling,
including the time between consecutive locations (Swihart and Slade 1985), the number of
observations used to determine the analysis (Borger et al. 2006), and the technique used to
collect data. A principal step in using home range analysis for radio telemetry studies is
establishing an appropriate sampling protocol. Sample size and autocorrelation of data influence
the estimation of home ranges. Two types of sample size need to be considered, the first is
biological sample size; the researcher assumes that data are representative of the movements
exhibited for the defined time period sampled. To ascertain the validity of the collected data,
knowledge of the biology of the animal is required. Second, having an appropriate statistical
sample size provides the best results from the home range estimate. Considerable discussion
exists in the literature regarding the use of home range concept, its analyses and its usefulness to
biological studies (White and Garrot 1990, Otis and White 1999). Autocorrelation of animal
movements and the concept of time to independence has been a recent focus of scrutiny because
of their influence on the results of statistical analyses (Powell 2000, Kenward 2001). However,
subsequent evaluations have demonstrated removing autocorrelation can remove the biological
signal of interest (De Solia et al. 1999, Otis and White 1999). In fact, recent studies illustrate we
need to understand autocorrelation better, as a large amount of biological information is
contained in the spatial and temporal autocorrelation structure of animal movements (Cushman
et al. 2005, Kie et al. 2010). Animal behaviour is nearly always temporally autocorrelated; it is
suspected autocorrelated location points will show more relevant behavioural information than
independent data points would (Gurarie et al. 2009, Boyce et al. 2010). Others believe the
structure of autocorrelation data should be understood for it may provide insights into
interpreting the data (Cagnacci et al. 2010). For example, spatial data collected by GPS
telemetry is often autocorrelated because of the structure of the topography, geology, soils,
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hydrology and vegetation (Boyce et al. 2010). For this reason much of the spatial
autocorrelation in animal use data can be attributed to the characteristic of highly autocorrelated
landscapes.
Three methods are presented to explore the use of models attempting to include behavioural and
movement processes of habitat selection: graph theory, step selection functions and Brownian
bridge movement model. A fourth method, resource selection models reflect behavioural and
movement processes and are popular resource use models.
Resource Selection Function
Resource selection functions (RSF) are models that estimate the probability of use of a resource
and are able to achieve statistical rigor because the models are constructed using data (Boyce et
al. 2002). Studies using RSF compare resource use of animals to the availability of those
resources on the landscape (Manley et al. 2002). Models of RSF can be designed from presence
/ absence data, but in telemetry studies this may be challenging because lack of telemetry
relocation data does not necessarily signify lack of use. Boyce et al. (2002) proposed the use of
presence / available data instead of presence / absence data. A system of three different resource
selection study designs for telemetry studies that incorporates used versus available data was
suggested by Manley et al. (2002). Design I states available and used resource units are both
defined for the complete population of animals being studied. For Design II, the available
resource units are assumed to be the same for the whole animal population but the used units are
set at the individual level. In Design III available and used resource units are identified for
individual animals.
A resource unit is defined as a sampling unit of the landscape (e.g. pixel, or grid cell). It is
comprised of predictor variables (covariates) which are habitat attributes that may be used to
predict the relative probability of use for a resource unit (Manley et al 2002). Response variables
can be stated as animal responses such as resource selection, home range use or survival, and
predictor variables are usually environmental conditions such as elevation. The modeling
process searches for the most parsimonious model from a collection of possible models. The
most parsimonious model is described as model with sufficient parameters to avoid bias, but not
too many that precision are lost (Burnham and Anderson 1992). Parsimony can be measured by
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statistical indices such as Akaike’s Information Criterion (AIC) and the model with the lowest
AIC is deemed to be the most parsimonious model from a group of models. Models attempt to
establish a solid basis for understanding a system; they are simplifications of real world systems
and have clearly stated assumptions that can be used for testable hypotheses (Starfield 1997).
There are a number of sampling designs to estimate an RSF, for example, a random sample of
resource units could be drawn and evaluated for the presence or absence of an animal (Boyce and
McDonald 1999). Model coefficients can be estimated using logistic regression if occurrence is
recorded as absence / presence (0,1), or a link function could be used for count data, such as
Poisson regression or zero-inflated Poisson regression (Nielson et al. 2005). An alternative
method is to use a sample of occupied resource units to contrast with a random sample of
landscape locations using logistic discrimination function (Decesare and Pletscher 2006,
Johnston et al. 2006). The predictive ability of the RSF can be assessed using the k-fold cross-
validation methods outlined by Johnston et al. (2006).
The RSF can be used in a GIS to plot the relative probability of animal use across the study area
at multiple scales (Boyce 2006, Bowyer and Kie 2006). This depiction of landscapes as a
probabilistic function is an alternative to binary maps of habitat versus non-habitat. Such
methods reflect a more complex understanding of the patterns of habitat use compared to a basic
binary characterization of habitat. In addition, the models may be used to detect habitat
associations of animals across scales (Boyce 2006). RSF models provide little insight about the
movement of animals, but they do enable the researcher to depict habitats that are probably
occupied by the study animal (Young and Shivik 2006). Using RSF’s in GIS provides a map of
areas of high probability of use and their proximity to one another, including areas of lower
probability of use.
However, some habitats identified by modeling as potential habitat may not necessarily mean the
habitats are productive and in the worst case scenario they may be a sink or obstacle to
movement (Kristan 2003), particularly if good habitat become sinks (Ronce and Kirkpatrick
2001). Although it is possible, or even likely, habitats may at times represent low quality habitat
that may still allow animals to move through them (Haddad and Tewksbury 2005).
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RSF models are useful tools in attempting to understand habitats used and preferred by animals.
Movement processes such as migration are determined in animals by a need for forage, to avoid
predators, to utilize seasonal resources, to find mates, and to expand ranges (Kamler et al. 2007).
Since movement is an obvious component of migration and dispersal it would be useful to
include it in the modeling process. Until recently, incorporating movement and behaviour in
models has been limited, partially due to the difficulty of quantifying them.
Graph Theory and Resource Selection Function
RSF’s have been designed to predict areas where animals have a high likelihood of occurrence
(Chetkiewicz et al. 2006). Areas of high RSF can be used to generate nodes or patches of
habitat, and then the inverse of the RSF can be used to produce a cost surface as a substitute of
movement using least-cost path analysis. The paths are validated using paths from out-of-sample
GIS location data. The modeling process aligned well with the GPS data movement paths,
validating the results (Chetkiewicz et al. 2006) . Graph theory is usually a depiction of habitat as
nodes making it possible to identify the nodes using a variety of techniques.
Step Selection Functions
Another method of combining movement process and landscape pattern in modeling applies
conditional logistic regression to quantify movement probabilities on landscapes using step
selection functions (SSF). The analysis technique is similar to RSF’s but instead of
characterizing telemetry relocation data points in an RSF, it compares steps, defined as a
segment between animal telemetry locations points on the land (Fortin et al. 2005). These
segments or steps are compared with random steps from the same starting point to model the
effects of landscape heterogeneity on movement and areas of high movement probability. Using
this method, researchers determined elk movements were affected by roads, cover and wolf
predation risk (Fortin et al. 2005). As well, high movement probability quantified by the SSF
may be used to investigate distance and direction of movement in a defined landscape which
would be valuable for linkage or corridor design (Chetkiewicz et al. 2006). Such analysis
techniques and modeling methods would be useful for understanding animal migration as well.
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Brownian Bridge Movement Model
Tracking a continuous path through space and time is the best method of quantifying movement,
but most animals cannot be tracked this way (Turchin 1998). For most wildlife studies the only
alternative is to use techniques such as GPS telemetry to collect locations at discrete intervals
along the path. Until recently the most common method of depicting these movement pathways
was to connect the location points with a line segment to depict the route (Berger and Berger
2006). Depicting animal movements using Brownian bridge movement model (BBMM) was
first done by Bullard (1999) in presenting animal home ranges. Horne et al. (2007) further
developed the model to use telemetry location points and associated error to develop a maximum
likelihood means for empirically estimating a variance term related to the animal mobility. The
BBMM is dependent on time-specific location data and the distribution of location error from
telemetry which is assumed to be normally distributed (Horne et al. 2007). An empirical
estimate of variance may be determined from location data used in the BBMM by assuming the
path connecting any two location points is a Brownian bridge.
BBMM is a method to model animal location points in space and time. It is a continuous-time
stochastic model of movement where the probability of being in an area during the time of
observation is conditioned on starting or ending locations. A BBMM is very applicable to
animal location data obtained by GPS or Very High Frequency (VHF) device with short time fix
rates. The process provides an empirical estimate of the movement path of an animal using
distinct location points collected at relatively short time intervals. The model also calculates
utilization distribution connecting each pair of successive locations, which is an estimate of the
relative time spent in an area during the time interval between those locations.
The BBMM is a good fit for describing space use of animals during migration or dispersal
(Horne et al. 2007, Sawyer et al. 2009). It models the uncertainty in the movement path between
telemetry location fixes along the migration path (Horne et al. 2007). Using location data
collected at short time intervals, the model spatially depicts important attributes of migration
routes such as stopover sites, movement corridors and the landscapes and habitats used for
migration (Sawyer et al. 2009). The model has a larger focus on estimation rather than
prediction like state-space models for analyzing and predicting animal movements (Morales et
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al. 2004, Jonsen et al. 2005). BBMM is based on the properties of a conditional random walk
between locations (Codling et al. 2008). Most animal movement is not truly random, so the use
of a model based on stochastic movement is justified (Turchin 1998, Horne et al. 2007). When
there is no other information available on how an animal moved from one point to another, the
Brownian bridge can be used as an approximation of the actual movement path. As the time
period between location pairs increases, the possibility of violating the assumption of random
movement is more likely. Once this occurs, random movements between locations will become
more and more unlikely and are more likely to reflect a biased random walk than a simple
random walk (Horne et al. 2007).
This may lead one to ask; what is the maximum acceptable time interval between locations? The
developers of the model stated there is no single answer that will apply to all situations (Horne et
al. 2007), but some factors will be related to differing animals mobility. For a more mobile
animal the utilization distribution will be less certain of the movement pathway than an animal
which is less mobile. So until these relationships of movement are further understood the
authors recommend users thoroughly evaluate if the assumption of a conditioned random walk
with a constant movement rate represents their data (Horne et al. 2007). Taking these
suggestions into consideration the model was developed using data with location fixes every
seven hours so one could assume, as did Sawyer et al. (2007) that it would work with 2hr
location intervals. Another model assumption is that the distribution of location error was
normally distributed and used a single estimate of the variance. Individual variance can be used
for each pair of points in the movement path. The calculations may be simplified by using a
single estimate of the Brownian motion variance for all pairs of locations, as done by others
(Sawyer et al. 2009, White et al. 2010). The probability distribution calculation of the animal
movement path is dependent on the distance between location points in space and time, the error
found with each location point, and the mobility of the animal (Horne et al. 2007). The one
parameter a researcher can consider in the study design is the time interval between locations. A
lower amount of time between successive points reduces the uncertainty of the actual path.
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LANDSCAPE CONNECTIVITY ANALYSES
Graphs are built of nodes (points) and edges (lines connecting the points). Two nodes joined by
an edge are considered connected. Habitat patches on a fragmented landscape are considered
nodes, with edges between considered possible movement pathways. These basic characteristics
of graph theory indicate why it has become an important tool in determining habitat connectivity
for conservation planning (Urban and Keitt 2001, Beir et al. 2010, Chetkiewicz et al. 2006).
Patch connectivity is commonly calculated as a complex function of the cost to move between
patches (Tischendorf and Fahrig 2001). These costs are usually considered to be a function of
the distance between patches. A simple and often used measure is the Euclidean distance or the
shortest distance from a patch to its nearest neighbor (Moilannen and Hanski 2001). Other
studies use more complex methods where all surrounding patches within a dispersal distance
contribute to its connectivity, in an isolation-by-distance manner (Hanski 1994). There is a
rudimentary understanding that in a landscape mosaic the matrix in between habitat patches such
as corridors, barriers, elements of fragmentation and land cover, to name a few, is an important
factor in determining movement of animals among patches (Richetts 2001, Schadt et al. 2002).
Habitat connectivity is a concept that forecasts the possibility of an animal to travel among high
quality habitat patches considering both the spatial arrangement of the landscape and the
animal’s movement behaviour as it responds to the habitat spatial structure (Taylor et al. 1993,
With et al. 1999, Brooks 2003, Fahrig 2007). Current studies on habitat connectivity have
described the importance of the relationships between the spatial structure and quality of matrix
between high quality habitat patches (Richetts 2001, O’Brien et al. 2006). The decision of what
path the animal will take is ultimately dependent on the animal’s behaviour and ability to move
through lower quality matrix structure (D’Eon 2002, Belisle 2005). The concept of including
aspects of the landscape matrix besides the presence of habitat needs a shift from a structural to a
functional connectivity measure because the effect of different landscape elements on dispersal is
species and behaviour specific.
To be effective, categorization of functional habitat connectivity needs to evaluate a landscape
with consideration of an animal’s perception of habitat connectivity (Wiens 1989). An animal’s
awareness of landscape spatial structure is expected to be primarily determined by aspects of
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fitness including mortality and reproductive success. Physical effort (Stevens et al. 2004) and
energy expenditure are two attributes that could affect fitness (Drielsma et al. 2007) experienced
by individuals using a variety of land cover types (With et al. 1997, Driezen et al. 2007). Cost
value represents the permeability of a grid cell for the movement of an individual species
(Villalba et al. 1998) within the framework. Permeability stands for the fraction of individuals
that would not be able or willing to cross the specific landscape attribute. It is not a measure of
speed, it is a measure of the reluctance to use habitat for movement (Schadt et al. 2002). A
method to quantitatively describe movement behaviour may be accomplished by applying
specific animal cost values of habitat to the matrix to reflect the ecological quality of habitat at
each cell to assess the cost to an animal moving through the matrix. Cost values are frequently a
representation of a number of environmental variables applicable to animal use of habitat such as
vegetation cover type, slope, water, elevation, roads and human developments.
Many studies assess cost values based on expert opinion (Clevenger et al. 2002, Johnson and
Gillingham 2004, O’Brien et al. 2006). Some studies use methods such as compositional
analysis where vegetation cells are rated based on species habitat preferences which is measured
by the amount of time the species spends in each land cover type compared to its availability in
the landscape (Kautz et al. 2006, O’Brien et al. 2006). Resource selection methods have also
been used to quantify habitat preferences by investigating the relationship of environmental
variables with occurrence data using regression models (Boyce and McDonald 1999, Manley et
al. 2002). The inverse of these indices of land cover use ratings can be used as a value for land
cover cost (Graham 2001, Chetkiewicz et al. 2006, Carroll 2010). Ideally, cost values should be
based on field studies. Land cover classes and the setting of cost values in the friction layer is
likely the most important step in the process of calculating effective distance; it is the link
between the GIS data and the ecological - behavioural aspects of animal travel. The development
of the least-cost modeling as an approach to incorporate detailed geographical information as
well as behavioural aspects as a measure for connectivity is in development (Graham 2001,
Schadt et al. 2002, Carroll et al. 2011).
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Least-Cost Path
The least-cost modeling process originates from graph theory and is commonly used in applied
land and species management projects and for research (Walter and Craighead 1997, Graham
2001, Schadt et al. 2002). It is relatively easy to use and the algorithm is available in many new
GIS packages. In the least-cost model, every landscape unit (grid cell) is assigned a friction
value related to its positive or hindering effects on the movement process being modeled.
Typically, an input into GIS for a least-cost model uses grid maps. Much of the GIS data, such
as linear infrastructure and habitat edges, are available in vector format that has to be converted
to rasters and combined with grid based information before use in the model. Since the grid map
is the only input, its quality has a large influence on the quality and reliability of the cost map
output. A number of aspects need to be considered when producing the input map. For instance,
relatively low resolution or large grid cells may be appropriate for general land cover since many
vegetative parcels have larger dimensions. Yet resolution is critical for smaller or narrower
elements on the landscape, such as roads and vegetative boundaries. In order to convert linear
and smaller elements accurately the grid cell size of the map should be smaller than the width of
the narrowest element in the landscape; otherwise smaller items may disappear from the grid and
linear elements may become discontinuous. There are two potential consequences to this, one is
corridors may become intersected by high resistant cells or important barriers may have holes
where the cost path will be allowed to pass through because one cell or two cells touching by
corners will allow the cost path to cross a barrier. Line elements either need to be portrayed at
their actual width or they could be converted to polygons using GIS by buffering the linear
attribute. The scale of the map should also fit for the species being studied. One means of
selecting appropriate scale would be to use a size larger than the known dispersal distance of the
animal (Walker and Craighead 1997). This becomes important for including the landscape
surrounding the study area in the analysis (Carroll et al. 2011, Koen et al. 2010); particularly for
elements and potential source patches for the species outside the study area which may affect the
analysis results. One short fall of least-cost modeling procedures is that they always produce
least-cost corridors by depicting the lands that provide lower resistance to animal movement, but
these paths for animal movement and connectivity may still be poor (Jenness et al. 2010).
Although least-cost path modeling methods are popular, it is widely recognized wildlife likely do
not travel along a single path of least resistance and likely the amount of travel distance is much
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larger (Theobald 2006). Current applications of least-cost methods are modeling multiple
pathways, ranking their importance which provides multiple possibilities of connectivity for
consideration in the planning exercise (Beier et al. 2008, Carroll et al. 2010).
Current Flow Analysis
Circuit theory is a recent method developed to understand patterns of gene flow and animal
movement for development of a linkage. GIS is used to portray the landscape as a grid of
squares with each grid called a raster and each square a pixel. Resistance values are assigned to
each pixel as a function of pixel properties such as land cover, topography and human
disturbance level. Resistance layers should be developed individually for each focal species
because assigned attributes may not affect movement of every species the same way when more
than one species is used in the analysis. This type of resistance raster is similar to the resistance
raster used in least-cost modeling in that they are usually estimated using expert opinion and
habitat use based on the literature. Resistance values in circuit theory are considered the
reciprocal of movement probabilities and do not reflect energetic cost.
Typically, circuit theory models require application of a “current source” at one end of a core
habitat block and a “ground” at the destination core habitat block, and are then modeled for
“current flow” (McRae et al. 2008, Carroll et al. 2011) . This is assumed to be equivalent to the
number of animals passing through each pixel as they disperse from one core habitat to the other.
Movement channeled into a narrow area is represented as a pinch point so it is highlighted by the
model Advantages of circuit theory are that it reflects the potential for the entire landscape of
study to support animal movement as a graded map rather than a polygon that categorizes every
pixel as either inside or outside the corridor. Pinch points represent weak points along the
linkage, and it has the same data requirements as least-cost modeling. Even though circuit
theory maps provide a wide range of movement possibilities about landscape connectivity, the
map does not classify a distinct corridor (McRae et al. 2008). In fact, a polygon with areas of
highest flow under current conditions may be a poor corridor because its potential to support
animal movement will decrease in an unpredictable way when land outside the corridor is
compromised by a conflicting land use. In contrast, a least-cost corridor does not change when
land outside the corridor is impacted by development. Another possible drawback is that circuit
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theory demarcation of flow may not highlight the best area to conserve a linkage. A linkage
with a pinchpoint would have contracted flow, but a linkage without the constriction of a
pinchpoint is an area of unconstrained flow and would be a better linkage to conserve. Both
circuit theory and least-cost modeling do not consider the impact of mortality on successful
movement (Tracey 2006). As it is now understood, circuit theory is a comprehensive method
and one of the better analyses to depict landscape connectivity to identify the degree of threat to
a linkage (McRae et al. 2008).
The literature regarding landscape connectivity suggests modeling based on the spatial
arrangement of habitat and animal habitat preferences could be improved by using new methods
to quantify animal movements based on behaviour, which would improve our understanding of
movement events such as migration to ensure their conservation (Horne et al. 2007, Kenward
2001, Turchin 1991). Enhancing this understanding with movement behaviours will enable
researchers to better predict habitat use particularly for dispersal and migration. By studying
successful movement and migration pathways of species it may be possible to identify which
variables are characteristic of existing movement corridors and apply those insights to predicting
areas of connectivity for species where movement corridors are not known (Chetkiewicz and
Boyce 2001). One possible method to accomplish this goal is to determine the spatial extent and
characteristics of a movement corridor used by a flagship species such as elk during migration.
This information combined with an understanding of the ecology of migrating elk could be used
to develop local scale management strategies to conserve the species, its migration pathways,
and, for a broader purpose, use the data to test the ability of an existing model to predict a known
functioning migration route. An understanding of elk migration metrics will be useful for proper
management of the human use on a landscape to benefit elk and their migration patterns.
Conservation biologists suspect the protection of isolated natural areas may not work for
biodiversity conservation and linking areas into connected networks is needed to attain
conservation goals, particularly if one considers climate change (Carroll 2010). Planning for
connectivity involves blending process and pattern, and connectivity can be maintained by other
methods besides corridors (Chetkiewicz et al. 2006). These are aspects which are relevant to
maintaining elk migration.
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Historical Management and Research of Castle-Carbondale Elk in SW Alberta
This section will summarize what has been recorded about the herd size, movements and
distribution of the elk populations inhabiting the Castle-Carbondale region. Elk have been
present in the Castle area for generations. Elk remains have been found in archeological sites in
nearby Waterton National Park (WNP) dating back several thousand years (WLNP files 1992).
Records of the North West Mounted Police from the 1870’s noted large numbers of elk in the
mountains and foothills west of Fort Macleod (Gibbard and Sheppard 1992). In the late 1800’s a
combination of disease, winters of cold temperatures and high snow loads, as well as over
hunting had depleted the elk to near extirpation. Elk are reported to be have been killed by an
unknown disease during 1879, possibly contracted from cattle (Gibbard and Sheppard 1992),
which combined with excessive hunting resulted in the mortality of all the elk in SW Alberta and
SE British Columbia (Gibbard and Sheppard 1992).
Castle-Carbondale Herd
In the Castle area, elk numbers were likely increasing during the 1920’s and 30’s because the
area was managed as a Game Preserve. A fire in 1936 swept through the region, opening up
large tracts of new habitat and the elk population quickly increased. By early 1950’s elk were
very common in the Castle with large numbers wintering in the O’Hagan, Carbondale Hill,
Mount Backus, Beaver Mines Lake area, and along the Castle and Carbondale River,
Screwdriver Creek, Byron Hill, Whistler Mountain and Maverick Hill. Land owners from that
time period estimated there were about 3,000 elk in the Castle-Carbondale area in 1953 (Gibbard
and Sheppard 1992). The areas status as a Game Preserve ended in 1954 and it was opened to
hunting.
Elk studies in the early 1990’s using VHF radio collars determined portions of this herd’s
summer range in the headwaters of the Carbondale and its tributaries, in the South and West
Castle with a few animals staying near the winter range year round. This herd is known to
intermingle with the Beauvais Herd (Morgantini 1992). Winter and summer seasonal home
ranges for the Castle-Carbondale herd are located in Wildlife Management Units (WMU) 302
and 400.
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CHAPTER THREE: USING BROWNIAN BRIDGE MOVEMENT MODEL TO DEPICT
ELK LINKAGE ZONES IN SW ALBERTA
ABSTRACT
Anthropogenic disturbance leading to habitat loss and fragmentation may have adverse impacts
on ungulate migration. Understanding the movement and dispersal patterns of elk (Cervus
elapus) on public lands will facilitate management and benefit elk and other uses of land
resources. I used a Brownian Bridge movement model (BBMM) to determine a probalistic
estimate of an elk population migration route, distinguishing between stopovers and movement
segments. My results of a partially migratory population traveling a modest migration distance
demonstrated that the population used stopovers during the spring and fall. Although a number
of seasonal stopovers were similar between spring and fall migrations, many differed. Migrations
corridors were used repeatedly between years with some used by more individuals than others. A
proportional use measure of use may be an appropriate method to prioritize migration corridors
for conservation. My findings suggest management strategies could be beneficial for
conservation of migration.
I
NTRODUCTION
Large herbivore migrations are globally considered threatened by human development. In order
to conserve this phenomena researchers have begun to investigate the effects of habitat
fragmentation, human disturbance, and the primary drivers of animal migrations (Berger et al.
2008, Harris et al. 2009, Hebblewhite et al. 2007, Mysterud et al.2001, Sawyer et al. 2009,
Voeten et al. 2009). Migration events are considered to be an ecological necessity for the
existence of populations and meta-populations, often essential to population genetics (Coulon et
al. 2006, Soule 1991) and allowing for increased access to resources for migrating species
(McCullough 1985, Schmiegelow 2007).
Elk (Cervus elaphus) migration, similar to numerous other species migration, is an adaptive
behavioural strategy that evolved to avoid limitations on resource availability (Cook et al. 2004,
Dingle 1985, Hebblewhite 2008) and to reduce potential predation risk (Fryzell and Sinclair
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1988, Hebblewhite 2008). Seasonal movements by elk, from low elevation winter range to high
elevation mountain ranges provide elk an opportunity to respond to climatic variation, following
elevation gradients as they track optimal patches of nutrient rich vegetation for an extended time
period, enhancing fitness and reproduction (Boyce 1991, Morgantini and Hudson 1989,
Mysterud et al. 2001, Phillips and Alldredge 2000, Smallidge et al. 2010). In turn, elk contribute
to ecosystems function by their grazing pressure on plants and influence on soil dynamics (Frank
and Goffman 1998, Kie and Lehmkuhl 2001, Schoenecker et al. 2004). Elk foraging activity is
part of a phenomena of top down trophic cascades, considered a prevailing explanation of
riparian plant recovery as a result of decreased browsing by elk due to increased predation by a
reintroduced wolf population in Yellowstone National Park (Ripple 2007, Ripple and Beschta
2004).
Beyond the ecological influences of elk distribution and densities to the land, an understanding
of the growing effects of human disturbance is a prerequisite for management and distribution of
elk populations (Lyon and Ward 1982, Millspaugh et al. 2001). Research has shown human
activities requiring or creating roads caused avoidance responses by elk to the human use of
roads (Cole et al. 1997, Frair et al. 2008, Lyon 1983, Rowland et al. 2000), including land uses
and recreation (Cassier et al. 1992, Ferguson and Keith 1982, Morgantini and Hudson 1985,
Naylor et al. 2009). There have been indirect habitat losses caused by avoidance of roads and
trails by elk in both protected and non-protected public lands (Gagnon et al 2007, Naylor et al.
2009, Rogala et al. 2011). While studies of elk populations in areas of no elk hunting such as
those on private land or of protected areas noted human activity indirectly created a spatial
refuge (Hebblewhite et al. 2005). Others have determined elk can benefit from industrial activity
such as timber management (Rumble and Gamo 2011) and road management (Cole et al. 1997,
Forman et al. 2003, Frair et al. 2008). Road management by decommissioning roads or using
gates to control access is beneficial to many species including elk (Frair et al. 2008, Northrup
2010). These documented effects of human activity indicate that an increase in human land use
without planning for wildlife habitat use and movement requirements may have adverse or
beneficial effects to migrating elk and landscape connectivity for wildlife.
Numerous types of human activity such as roads, resource extraction, residential development,
and other forms of habitat alteration can reduce the landscape connectivity required for migration
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and dispersal between meta-populations (Friar et al. 2008, Gagnon et al. 2007, Lyon 1979,
Rowland et al. 2000). Understanding what degree of landscape connectivity is essential to the
greatest diversity of species and at-risk animals is an evolving science. Understanding migration
movements and dispersal patterns of elk on public lands and factors that affect these movements
will facilitate elk management and help to develop management strategies to benefit elk and
other species using land resources (Benkobi et al. 2005).
SW Alberta Case Study
In southwest Alberta, the home range of the Castle-Carbondale herd is located in an area
administered under multiple jurisdictions in Alberta and British Columbia. Winter range is on
Alberta public and private lands while summer range is public land located in both Alberta and
British Columbia. Both elk seasonal ranges have experienced decades of use for cattle grazing,
gas extraction, timber harvesting, off-highway vehicles and hunting. On public lands there is an
increasing human disturbance footprint due to recreational activities and resource extraction.
Such a multi-use management strategy results in an increase of infrastructure, human activity,
road density and traffic on roads which have the potential to reduce landscape connectivity,
crucial to many species including migratory elk (Dodd et al. 2007, Forman 2003, Lyon 1979,
Rowland et al.2004, Trombulak and Frissell 2000). Road densities in the Castle-Carbondale are
at levels known to affect elk movements (.55km/km
2) (Rowland et al.2004, Frair et al. 2008). In
the Castle / Carbondale, predation risk is from a wide variety of carnivores such as grizzly bears,
black bears, cougars, wolves, lynx, and coyotes. Human hunting appears to be the largest source
of elk mortality.
Elk migration in SW Alberta is similar to many western ungulate populations in North America
(Boyce 1991, Hebblewhite et al. 2008, Sawyer et al 2009, White et al. 2010) as elk migrate from
low elevation winter ranges to high elevation mountain summer ranges (Morgantini 1995,
Sheppard 1992). Rocky Mountain elk in southwest Alberta annually migrate to seasonal ranges,
a round trip distance of 12 to 100 km, with one male elk from the Porcupine Hills herd migrating
300+km two consecutive years across provincial and international boundaries. Elk management
in my study area has focused on population numbers, controlled by limited hunting permits for
female elk and an open season using a selective harvest strategy for multi-branched male elk.
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Winter range management involves restricted industrial activity during the winter months and
defined stocking rates for cattle for summer grazing. Very little is known about elk summer
range use or migration pathways. To effectively manage a partially migratory elk herd,
managers require data to determine if preferred migration routes exist, what are the important
route characteristics and whether they need to be conserved.
Understanding the migration and dispersion patterns and underlying factors affecting each
should facilitate elk management. In my study area blocking or reducing connectivity of
migratory movement routes could result in elk spending more time on wintering grounds located
on private lands than on traditional ranges within provincial forest reserves (Joslin and Youmans
1999, Morgantini and Hudson 1985). Such displacement of elk has led to increased public
perceptions of an overabundance of elk (Torstenson et al. 2002). A reduction in connectivity for
migration can lead to changes in distribution (Hebblewhite et al. 2008, Rowland et al. 2000)
increased elk use of a limited winter range and ultimately result in increased land owner
difficulties from crop depredation. Additional consequences could be ecological losses and a
reduction in habitat quality of critical winter habitat due to over grazing (Walter et al. 2010),
effects to elk calving success (Phillips et al. 2000), potential reduction of elk fitness (Bender et
al. 2008, Boyce et al. 2010, Stewart et al. 2010) and artificially decrease population size (Webb
et al. 2011). Migration can enhance survival and recruitment by reducing predation risk (Fryzell
and Sinclair 1988, White et al. 2010). In other circumstances elk may chose not to migrate due
to increased potential of predation risk during migration and / or other land use or management
changes which improve security from predators or increase availability of high quality forage on
the winter range (Hebblewhite et al. 2006, Hebblewhite and Merrill 2007).
Based on my studies, Rocky Mountain elk in southwest Alberta annually migrate to seasonal
ranges, a round trip distance of 20 to 100 km, with one male elk from the Porcupine Hills
subpopulation (herd) (Clark 1993) migrating 300
+km two consecutive years, across provincial
and international boundaries (Paton unpublished). The range of migration distances for the
Castle-Carbondale subpopulation is 15 to 64 km. Increasing development and human activity
may impact areas of elk migration because they utilize much of the land base where the
increased human activity is most prevalent. Elk migration occurs on transitional range between
winter and summer range.
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The Castle-Carbondale subpopulation is one of seven subpopulations (herds) in SW Alberta
representing a total population of approximately 4,300 elk. I used GPS collars to track
relocations of 68 elk in the Castle-Carbondale herd of 650 animals from 2007 to 2010. A total of
21 elk were harvested by hunters or preyed upon by carnivores in their first season of collaring,
resulting in 50 collars collecting adequate migration data for analysis. Individual elk were
tracked for at least a two year period during a four year study acquiring relocation points every
two hours. I use an investigative framework (Sawyer et al. 2009) applying the Brownian bridge
movement model (Horne et al. 2007) to delineate and prioritize the population migration
network. The BBMM analyses use migration GPS data to identify elk migration ecology such as
movement corridors between habitat patches known as stopover areas which are expected to be
important to elk for increasing body condition, resting, and calving (Horne et al. 2007, Sawyer et
al. 2009, Sawyer and Kaufman 2011).
The Castle-Carbondale elk migrate up to 34km straight line distance from their winter range, a
montane / agricultural landscape to high elevation summer range in the Crown of the Continent
along the Continental Divide of Alberta, Canada. Migration attributes in this region are poorly
understood. I hypothesize:
• Elk migrate along specific pathways each year without stopping over because the
migration distance is relatively short, traversable by elk in a day or two.
• Fall migration pathways would diffe r from spring migration pathways;
• Male and female migration would spatially differ, possibly from sexual
segregation.
STUDY AREA
The Castle-Carbondale study area encompasses approximately 1,000 km2 in southwest Alberta.
It represents a large component of an internationally recognized area known as the Castle Crown
of the Continent (Figure 3-1). Alberta Environment and Sustainable Resource Development
administer 100% of the public Forest Management Area. On the eastern boundary of the
provincial forest reserve are private ranchlands intermixed with cropland. The study area
includes portions of two municipal districts (M.D. Pincher Creek, Municipality of Crowsnest
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Pass). Livestock grazing occurs seasonally on public land and year-round on private land.
Industrial activities in the area include forestry and natural gas extraction. Extensive human
activity on the landscape is widely distributed, primarily from random camping, off-road
vehicles, mountain biking, hiking, hunting, and fishing combined with winter activities of
snowmobiling and skiing. The greatest human use in the study area occurs on public lands
during the summer recreational season where limited enforceable restrictions apply and staff
resources to enforce the existing regulations are few. The elk are hunted during September to
November. Grizzly (Ursus arctos) and black bear (Ursus americanus), cougar (Puma concolor)
and coyotes (Canis latrans) are potential predators in SW Aberta. Wolves (Canis lupus) are
found in the study area with a small pack raising young during the duration of the study.
Migratory elk summer range is entirely on provincial land while winter range includes both
private and provincial land. There are 2,273 km of roads in the study area with a density of
1.3km/km2 on private land. The multi-use provincial land portion of the study area has a density
of 0.55 km/ km2 of roads.
Elevations range from 1250 to 2330 m. The four kilometre wide strip of private land on the
eastern boundary represents transition range between grassland and montane, continuing
westward along montane foothills, which quickly rise to subalpine and alpine environments of
high elevation mountains along the Continental Divide between Alberta and British Columbia.
Transitional range is the montane habitat found between the summer sub-alpine/alpine and
montane winter ranges where migration routes occur. The area is composed of two natural
regions and three natural subregions. The Rocky Mountain natural region is comprised of the
Montane and Subalpine subregions and the Grassland natural region includes the Foothills
Fescue subregion. Environmental characteristics of the Rocky Mountain natural region include
cool summers (13.9 C), short growing season, high annual precipitation (798 mm) and the
highest snow loads found in Alberta (Downing and Pettapiece 2006). The landscape is shaped
by the prevailing Chinook winds, which create snow-free southwest facing slopes exposing
winter grass and shrub forage for ungulates. Montane and Subalpine subregions consist of
rugged terrain with elevations from 825 m to 2,300 m. Dominant vegetation is lodgepole pine
(Pinus contorta) Douglas fir (Pseudotsuga menziesii), aspen (Populus tremuloides), subalpine fir
(Abies lasiocarpa) interspersed with grassland slopes, meadows, wetland complexes (Downing
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and Pettapiece 2006) and clearcuts. The Foothills Fescue subregion typically is rolling hills
(elevation 800 m to 1,525 m) dominated by mountain rough fescue (Festuca campestris),
bluebunch fescue (Festuca idahoensis) and Parry’s oatgrass (Danthonia parryi). Portions of the
subregion in the eastern portion of the study area have been converted to cropland or tame
pasture grass species.
Figure 3-1 Study Area for Castle-Carbondale Elk, 2007 – 2010 (location 694298 E 5483627 N)
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MATERIALS AND METHODS
Capture, Collaring, and Data Collection
I used a helicopter and net-gun to capture 68 male and female elk aged 1 – 18 years on the winter
ranges of southwestern Alberta from January to March during 2007-2010 (University of Alberta,
Edmonton, Alberta, Canada. Animal Care Protocol number #536-1003 AR University of
Alberta) (Fig.2-1). Elk were blindfolded and hobbled to allow collaring and sampling with low
impact to the elk. Elk were fitted with Lotek 4400M GPS, 4400 GPS/Argos collars (Lotek,
Newmark Ontario, Canada) and GEN4-GPS (Telonics, Mesa Arizona) equipped with mortality
sensors that increased pulse rate if the collar remained motionless for >6 hours. GPS units were
programmed to obtain location fixes every two hours (i.e. 12 per day). I located radio-collared
elk from access roads at least once a month and some herds such as the Castle-Carbondale every
week to confirm location and status. Collars from elk that died were refitted on new elk. The
collars were outfitted with a remote drop off device programmed to disengage after 104 weeks.
If the device failed, elk were recaptured annually by the helicopter using a net-gun method to
retrieve the collars. Collar data were not used if elk were harvested during the hunting season in
the first fall of collaring, if killed by predators, or collars failed before the first year of migrations
were complete (one spring and fall migration defined a migratory elk), or if the elk was a
resident or animals dispersed to another area.
Criteria to Determine Migratory Status of Elk
Elk populations such as the Castle-Carbondale herd are partially migratory, where one segment
of a population undertakes seasonal migration while the other remains on a single range
(Hebblewhite 2006, Lundberg 1988). Within a population of elk there may be a number of
different phenotypes (Boyce 1991). In the partially migratory Carbondale-Castle herd there are
migratory, resident and dispersal phenotypes. I assigned phenotypes as defined by Boyce
(1991). Elk with seasonal home ranges overlapping entirely or predominantly were defined as
resident elk. Migratory elk will move from a winter range to a separate summer range and return
to the same winter range, whereas dispersing elk will leave the winter range to another separate
seasonal range, not returning to the original winter range.
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Table 3-1 Collared elk from the Carbondale-Castle herd 2007 – 2010
Elk ID Capture date Herd Phenotype* Sex Age
E1 11-Jan-07 Carbondale
M F 8
E2 11-Jan-07 Carbondale M F 6
E3 11-Jan-07 Carbondale M F **UK
E4 11-Jan-07 Carbondale M F 1
E5 11-Jan-07 Carbondale M F 13
E6 11-Jan-07 Carbondale M M 1
E7 12-Jan-07 Carbondale M M 1
E8 12-Jan-07 Carbondale M M 1
E9 12-Jan-07 Carbondale M F 4
E10 12-Jan-07 Carbondale M M 1
E11 11-Jan-07 Carbondale M F 9
E12 11-Jan-07 Carbondale M F UK
E13 11-Jan-07 Carbondale M M 1
E14 11-Jan-07 Carbondale M M 1
E15 11-Jan-07 Carbondale D M 1
E16 12-Jan-07 Carbondale M F 1
E17 12-Jan-07 Carbondale M F 15
E18 11-Jan-07 Carbondale M F 9
E49 13-Jan-07 Carbondale R F 5
E51 4-Feb-08 Carbondale M F UK
E52 4-Feb-08 Carbondale M F 14
E53 4-Feb-08 Carbondale M F 4
E54 4-Feb-08 Carbondale M F UK
E55 4-Feb-08 Carbondale M F UK
E56 21-Feb-08 Carbondale M F 2
E57 13-Feb-08 Carbondale M F 4
E58 4-Feb-08 Carbondale M F 4
E59 4-Feb-08 Carbondale M F 7
E60 4-Feb-08 Carbondale M F 1
E61 21-Feb-08 Carbondale M F 4
E62 4-Feb-08 Carbondale R F 14
E63 4-Feb-08 Carbondale M M 1
E66 4-Feb-08 Carbondale M F 5
E67 21-Feb-08 Carbondale M F 2
E74 21-Feb-08 Carbondale M F 4
E75 21-Feb-08 Carbondale M F 4
E76 4-Apr-08 Carbondale M M 1
E77 21-Feb-08 Carbondale M F 16
E78 4-Feb-08 Carbondale M M 1
E79 21-Feb-08 Carbondale M F 14
E81 4-Apr-08 Carbondale D M 1
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*Phenotype code *UK - Unknown
M – Migrant
R – Resident
D - Dispersal
I examined data from each individual to assess if they moved between separate seasonal ranges.
Seasons were evaluated based on inflection points similar to Ferguson and Elkie (2006) using
rates of movement and steady directional movement to the seasonal ranges. By plotting
individual elk migration location points I determined the seasonal elk distribution patterns for
99% of the elk fit into the date segments identified for winter as January 1 - March 15, spring
migration (April 1 – June 15) summer (June 16 - August 30), fall migration (September 1 -
December 15). Selecting these dates to represent periods of elk seasonal use seemed logical since
Elk ID Capture date Herd Phenotype Sex Age
E82 4-Apr-08 Carbondale M M 1
E90 21-Feb-08 Carbondale M F 8
E95 26-Mar-09 Carbondale M M 1
E97 18-Mar-09 Carbondale M F 4
E98 20-Mar-09 Carbondale M F 5
E99 18-Mar-09 Carbondale M F 2
E100 20-Mar-09 Carbondale M F 1
E102 18-Mar-09 Carbondale M M 1
E103 26-Mar-09 Carbondale M F 14
E104 18-Mar-09 Carbondale M M 1
E106 20-Mar-09 Carbondale M M 1
E107 20-Mar-09 Carbondale R F 7
E110 20-Mar-09 Carbondale M F 7
E111 20-Mar-09 Carbondale M F 4
E115 10-Mar-10 Carbondale M F 16
E116 10-Mar-10 Carbondale M F 10
E117 10-Mar-10 Carbondale M F 15
E118 10-Mar-10 Carbondale M F 18
E119 10-Mar-10 Carbondale M M 1
E120 1-Apr-10 Carbondale M F 9
E121 10-Mar-10 Carbondale M F 4
E122 1-Apr-10 Carbondale M F 9
E123 10-Mar-10 Carbondale M F 3
E124 10-Mar-10 Carbondale M F 4
E126 10-Mar-10 Carbondale M F UK
E127 10-Mar-10 Carbondale M F 3
E130 1-Apr-10 Carbondale M M 1
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they represent the seasonal transitions of migration as determined by the data. Similar dates are
used in other migration papers (Benkobi et al. 2005, Zhi-gao et al. 2008, and White et al. 2010).
For the period of September 1 to December 30, numerous Castle-Carbondale elk moved between
seasonal and transitional range many times during hunting season making it difficult to assess
migration movements. In these cases elk would initially start migration going part way to the
winter range or to the winter range but return back to the summer range, possibly from hunting
disturbance. Later in the season the elk would eventually migrate back to the winter range. It was
the final movement to the destination range that I used in my migration analyses. January 1 to
March 15 is the core time period of winter range when elk were found within the 50% kernel
from 2007 – 2010. Small numbers of collared elk began moving westward towards summer
range soon after March 15 with most migrations starting in early May and completed by early
June. Based on my data review, and observations of the elk herd these dates were considered
representative of Castle-Carbondale elk migration and for relocation points needed for the
Brownian bridge movement model to spatially depict elk migration.
Kernel estimation of 95% was used to delineate seasonal winter and summer ranges. To
determine seasonal ranges I used the Home Range Tools (Rodgers and Kie 2010) 95% fixed
kernel with a band width of .8 (Kie et al. 2010). Animals were classified as migratory if the 95%
fixed kernel summer and winter range isopleths did not overlap in extent (Figure 3-2). This
method is repeatable and defensible given the biological question of seasonal ranges overlapping
or not (Jacques et al. 2009, Kie et al. 2010). I chose to allow multiple polygons of the 50%
isoline if the kernel created clustered polygons when calculating the core winter and summer
seasonal ranges. I used the mean easting and northing based on the UTM coordinates of the
location of each elk during winter and summer to measure the center of activity (Hayne 1949,
Nicholson et al. 1997).
Initiation of migration was defined as the date the animal began a directed movement toward the
summer range or winter range (Nicholson et al. 1997, White et al. 2010), depending on migration
season, continuing on to the destination seasonal range. End of migration occurred when the
migration pathway passed <1km from the median UTM location of the seasonal range the elk is
migrating to (Evan et al. 2005, Grarrott and White 1987). Typically the elk would reach the
centroid of a seasonal range within 24-hoursafter crossing the outer isoline of the seasonal range.
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Figure 3-2 Methods used to determine separate resident elk, migrating elk and dispersing elk
phenotypes using seasonal home range analyses (Boyce 1991)
Resident elk – seasonal Migrating elk – separate Dispersing elk - separate
ranges overlap ranges, 2 way movement. ranges, no return to winter.
Elk Migration Data and Characteristics
From 2007 – 2010, 68 elk were collared; 19 in 2007, 24 in 2008, 12 in 2009, 13 in 2010. An
attempt was made to capture elk from a variety of areas and groups distributed within the 153
km2 winter range. Location collection of 325,396 GPS location points from 68 elk occurred
from January 10, 2007 to December 30, 2010. I considered radio-collared elk as the
experimental unit to allow for population-level inference (Erickson et al. 2001, Johnson et al.
2000, Otis and White 1999). Random sampling of animals was attempted (Otis and White 1999)
by directing helicopter capture crews to collar individuals from different groups of elk located
across the entire extent of a herd’s foothill winter range.
To maximize sampling intensity I chose to collect two hour location fixes with the collar
dropping off after two years. The collar was subsequently redeployed on a different elk. To
control location error of data used for analyses, data were sorted to select all relocations with
three-dimensional (3D) and two-dimensional (2D) values with a dilution of precision value <8
(Adrados et al. 2003, D’eon et al. 2005, Pepin et al. 2008, Rempel and Rodgers 1997).
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Characteristics of migration such as timing, travel distance, duration of travel, step length and
tortuosity of pathways provided data useful to interpretation of migration routes and behaviour of
elk during migration. Distance of migration was calculated by two methods. First as
displacement, the straight line distance between the first and last location points of the migration
pathway. Second, as the total distance travelled during migration. Calculated by summing all the
step lengths, which is the straight line distance between each two hour location point.
I selected step-length (i.e. distance between two hour relocations in metres) as a surrogate of elk
mobility (Morales et al. 2004). Step length was computed using ARCMAP 9.2 (ESRI Inc.,
Redlands, CA) using Hawth’s Tools extension (http:www.spatialecology.com/htools/).
Using paired t-tests, I compared metrics between migration seasons, including timing of
migration, days of migration, linearity of migration routes (defined as migratory displacement /
actual migratory path, ranging from 0-1), number of stopovers and step lengths between seasons
for the population and sexes. Migration location points used in the BBMM were consecutive
location fixes between the start of migration to completion.
Modeling Elk Migration Routes
I input elk seasonal migration location data in a Brownian bridge movement model (BBMM)
(Horne et al. 2007) to estimate individual elk utilization distribution (UD) for each seasonal
migration. BBMM requires time specific location data, an error estimate for the location data,
and grid-cell size for the UD output. My analysis with BBMM used two hour GPS relocation
data from the migration time period, with an error estimate of 20m and a grid cell size of 100m.
I had to use a 100m cell size because the BBMM script running in R statistical software was
unable to complete the calculations for 140 seasonal migrations due to memory limitations. A
sequence pathway of GPS location points were used from collar data collected between winter
and summer home ranges during each spring and fall migration (Sawyer et al. 2009) to produce a
BBMM graphic for each elk (Figure 3-3).
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Figure 3-3 Example of an utilization distribution estimated for individual elk during the 2008
spring migration.
High-use areas represent stopover sites identified by numerous relocation and tortuous
movements. Moderate use areas positioned between stopovers represent segments of
migration movements where elk moved quickly in one direction. Low-use areas
represent the areas of uncertainty for the probabilistic path.
The BBMM is a continuous time stochastic movement model, where the probability of being in
an area is conditioned on the distance and elapsed time between successive locations; the
location error and an estimate of the animal’s mobility is referred to as “Brownian-motion
variance” (BMV; Horne et al. 2007). Odd-numbered locations are considered independent
observations from the Brownian bridges connecting the even-numbered locations, the BMV can
be estimated by maximizing the likelihood of observing the odd locations (Horne et al. 2007).
Two assumptions associated with BBMM are: 1) location errors represent a bivariate normal
distribution and 2) the movement between consecutive locations is random. The assumption of
normally distributed errors is suitable for GPS telemetry, but the assumption of conditional
random movement between consecutive locations may become less probable as time between
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locations increases (Horne et al. 2007). Location data collected from elk were two hours apart,
and migration data collected at seven hour intervals were successfully applied to BBMM
analysis of caribou (Horne et al. 2007). Following the methods of previous studies (Horne et al.
2007, Sawyer et al. 2009), I consider the assumption of conditional random movement to be
reasonable. Uncertainty of the actual pathway is integrated in the model using two ecological
attributes of travel: the animal’s mobility and a measurable location error (Horne et al. 2007,
Sawyer et al. 2009). Calculations of BBMM were computed in R language for statistical
computing (R Development Core Team 2009).
Migration routes modeled for the elk populations with BBMM are unique for they consider two
metrics of migration behaviour: 1) time spent in an area and 2) rate of migration. Both metrics
are used in this study to characterize high use areas where elk spent most of their time moving
slowly, not moving or following a tortuous route, possibly foraging or resting, parturition in
transition areas or during the spring waiting for snow depth to decrease allowing upward
elevation movement to summer ranges. Moderate use areas are represented by areas where elk
spend the least time and move quickly (Sawyer et al. 2009). From this I assume high use areas
reflect stopover sites, likely used for foraging and resting habitat or security cover, while
moderate use areas located between stopover sites represent migration movements (Sawyer et al
2009). Similar to other models (Forester et al. 2007, Frair et al. 2005, Johnson et al. 2002,
Morales et al. 2004) the BBMM model output is based on the assumption that behavioural states
such as migration movement and stopover events can be inferred from movement rates (Saher
and Schmielgelow 2005). Validity of the assumption depends on the frequency of the movement
data, behaviour types to be determined, and the potential such behaviours can be distinguished
by movement rates (Boyce 2006, Nelson et al. 2004). One important difference between BBMM
state-space process models is its focus on utilization as opposed to prediction (Horne et al. 2007),
making it a good compliment to predictive models.
Estimating Population Level Migration Routes
I used the BBMM developed in the R language for statistical computing (R Development Core
Team 2007) provided by Sawyer et al. (2009). After the UD (Utilization Distribution) of
separate seasonal migration routes for each individual elk were calculated, I selected elk with >1
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seasonal migration collected (n=50 elk), summed the cells values of all individual UDs and
rescaled their cumulative pixel cell values to a sum of one, so the migration route of each elk was
represented by one UD (Sawyer et al. 2009). I used the same rescaling process with the UDs of
all elk to create an estimation of the multiple migration paths used by the Castle-Carbondale elk.
Once the UDs were pooled, the BBMM (Brownian bridge movement model) output provided an
estimate of the relative amount of use across the population level route (Sawyer et al. 2009).
Population level migration route UD values were put into 25% quartiles with the top 25%
classified as high use and represented areas along the migration route where animals spent the
most time. I assumed these areas were used for foraging or resting when elk moved slowly.
Lower use areas represent movement corridors between stopover sites (Sawyer et al. 2009).
Unlike other studies (Horne 2007, Sawyer et al. 2009, White et al. 2010), spring and fall
migrations for many of the elk in my study did not follow the same route, so I pooled the two
seasonal migration data sets together for the first BBMM analysis of the population. For
comparison I separated fall and spring migrations for all elk then modeled these routes using the
BBMM to visually evaluate if outputs differed. I collected data for fewer fall migrations due to
harvest of elk, primarily of males.
To facilitate ranking of the conservation value of population migration routes, I assumed that
route segments used by a higher proportion of the population had higher conservation value than
portions used by a smaller segment of the population (Sawyer et al. 2009). I determined the
proportion of sampled population that used each route segment by using a script in R (Neilson
2009) to calculate how many of the individual migration routes (99% UD) occurred within each
100 x 100m cell of the estimated population level route. Therefore cell values ranged from one
to a potential maximum value equal to the total number of marked elk undertaking migration.
Migration routes used by >10% of the sampled population were considered to have higher
conservation priority than others. This 10% criterion was subjective decision intended to reflect
routes used by more than one marked animal. Sawyer et al. (2009) suggested this to be an
appropriate metric in the absence of a metric directly related to fitness.
I investigated whether the BBMM could be used to identify differences between male and female
migration UD during spring or fall. Since my data consisted of both male and female elk, there
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was the possibility the two sexes were using the landscape differently during migration,
particularly during the hunting season when males are managed by an open season for males
with three antlered branches or more and females are harvested by issuing a limited number of
permits (n= 99 permits) (ASRD 2007-10). In some populations, male and female elk are known
to display sexual segregation where males and females use habitats in their home ranges
differently (Bleich et al. 1997, Gregory et al. 2009, Main et al. 2008, Ruckstuhl and Neuhaus
2002). I modeled migration UD’s of male and female for both seasonal migrations to assess if
there may be a visual difference in the BBMM migration UD’s. The same evaluation method
was used to compare spatial locations of stopovers from the BBMM, used by male and females
for each seasonal migration. I used telemetry locations from all migratory elk to evaluate
selection and fidelity to specific ranges.
RESULTS
I captured a total of 68 elk during 2007-2010. Eighteen animals were censored from the analyses
due to mortality before one year of migration (n = 3), because they were residents (n =2),
dispersed (n = 2), or censored due to no or insufficient data (n = 10). A total of 50 collars (38
female and 12 male elk) collected satisfactory data during migration to be used for Brownian
Bridge Movement Model UD analysis. Collars collected a total of 325,396 telemetry relocation
points from 2007 – 2010, of which 31,332 were GPS points during migration. Eighty-eight
percent of the female elk were adults (two years or older) and 12% were yearlings (<2 years)
during the first year of monitoring. Male elk were all approximately 1.5 years old when
captured. The males only represented the age class of 3.5 years or less because I did not capture
elk greater than 1.5 years old due to the high capture mortality risks with multi-branched elk
during years of low snow depths.
During the four year study, two of the 21 collared elk died during migration as a result of
predation by wolves. Mortalities during all seasons of the study occurred from a variety of
sources including hunting and predators (Table 3-1). The total proportions of mortality sources
of collared elk in this study were 28% of the collared animals, consisting of males (n=9) and
females (n=10). The sample size of Castle-Carbondale elk we collared was reduced by 21% due
to hunting over four years of study, compared to 7.5% from natural predators (Table 3-1). Wolf
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predation of collared elk was low at 1 elk per year of study. There was one known active wolf
den in the home range of Castle-Carbondale elk. GPS telemetry locations from elk rarely were
found within 5km of the den site during the four years of study.
Table 3-1 Total number of elk mortalities (n = 21) and the mortality sources for the Castle-
Carbondale herd, 2007-2010
Elk ID Elk Sex Elk Age Cougar Wolf Hunter Capture Unknown
E2 F 6 1
E6 M 2 1
E7 M 2 1
E10 M 1 1
E11 F 10 1
E12 F n/a 1
E13 M 2 1
E17 F 15 1
E18 F 9 1
E53 F 4 1
E58 F 4 1
E61 F 4 1
E63 M 2 1
E76 M 2 1
E78 M 2 1
E79 F 15 1
E102 M 2 1
E104 M 2 1
E107 F 8 1
E111 F 5 1
E127 F 4 1
Total 1 4 14 1 1
I used 138 migration events (73 spring and 65 fall) for analysis. Spring migration sample sizes
were higher than fall migration because animal numbers were reduced by hunting and predation.
Castle-Carbondale elk moved a mean round trip of 38 km (straight-line distance) to three core
summer ranges. Thirty-three of the 50 migrating elk provided data for two - four summers
returning to the same seasonal range each year, typically using the same migration route to
summer ranges, but dispersing wider during fall migration. Pooled data from all years resulted
in a mean duration for linear migration of 20 +/- 1 days in the spring and 21 +/- 2 days in the fall.
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Castle-Carbondale elk spend approximately 11% of their yearly time in migration. Timing for
migration varied for individuals and across years. Mean departure date of all spring migrations
was May 2 (SD = +/-6.4 days, n= 73) and mean date of departure for all fall migrations was
October 20 (SD = +/-17.4 days, n=65). A number of characteristics of migration movement and
timing which may help understand elk migration characteristics and behaviour were summarized.
(Table 3-2 and Table 3-3).
Table 3-2 Migration metrics for Castle-Carbondale elk from 2007 – 2010
Season
Spring Migration metric 2007 2008 2009 2010
Number of elk 13 27 21 12
Mean Departure date 24-Apr 6-May 6-May 2-May
Minimum. Depart 3-Apr 13-Apr 28-Apr 19-Mar
Maximum Depart 23-May 16-Jun 20-May 2-Jun
Mean Arrival date 14-May 28-May 26-May 16-May
Minimum Arrival date 23-Apr 29-Apr 12-May 2-Apr
Maximum. Arrival 17-Jun 28-Jun 23-Jun 22-Jun
Fall Migration metric 2007 2008 2009 2010
Number of elk 11 27 15 12
Mean Departure date 6-Nov 31-Oct 22-Oct 24-Oct
Minimum Departure 30-Sep 15-Jan 26-Aug 23-Aug
Maximum Departure 17-Jun 21-Jan 2-Dec 25-Nov
Mean Arrival date 4-Dec 16-Nov 13-Nov 20-Nov
Minimum Arrival 13-Oct 21-Jan 8-Sep 4-Sep
Maximum Arrival 3-Feb 2-Feb 23-Dec 19-Dec
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Table 3-3 Characteristics of elk migration for movements and stopovers from 2007 – 2010
Season Migration characteristic N Mean
SE
(+/-) Minimum Maximum
Spring Migration days 73 20 1 2 65
Migration displacement (km) 20 1 6 34
Total migration path (km) 73 5 9 252
Migration linearity 0.34 0.02 0.05 1
Average step length (m) 370 140 170 830
Number of stopovers 8 1 2 17
Average distance between stopovers
(km) 3.4 .30 .7 13.4
Average distance between stopovers
(km) 12 1.3 2.8 8.4
Fall Migration days 65 21 2 1 68
Migration displacement (km) 18 1 5 32
Total migration path (km) 60 4 11 164
Migration linearity 0.38 0.02 0.04 0.76
Average step length .31 .14 .14 .60
Number of stopovers 7 2 1 17
Average distance between stopovers
(km) 3.7 .4 .4 21.3
Average distance between stopovers
(km) 12 2.5 3 16.4
I did not find significant differences between seasonal migrations for many of the migration
characteristics tested with a paired t-test. There were common patterns in the data with the mean
number of days of migration day consistent between spring and fall, yet between individuals the
duration of migration were quite variable (Table 3-3). Such a pattern of individual variability
was found in metrics such as total migration path, migration linearity, number of stopovers, and
average distance between stopovers (Table 3-3). I found average step length (m) for all elk to be
66 m different between fall (308 +/- 13.8) m and spring (373 +/- 13.81) m (two sample t-test, t =
-3.68, 63 d.f., p <.05). Spring mean step length of females was 58.7 m longer than their mean
step length during fall migration (-3.47, 52 d,f., p<5). Male elk step lengths were also
significantly different between fall and spring (-2.23, 10 d.f., p<5).
BBMM analysis provided a probabilistic measure of elk spring and fall population-level
migration routes and key stopovers. Areas of animal relocation stopovers are assumed to
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represent places of high elk use, while moderate-use segments are considered movement
corridors to the next stopover or a seasonal range (Figure 3-4). Mean estimate of the Brownian
motion variance for the elk population ranged was 3,533 m2 (SE +/- 977m2, n = 138 migrations).
A low use designation represented areas of variance or uncertainty of the BBMM calculation and
did not appear to be associated with stopovers or movement corridors (Sawyer et al. 2009).
Once I completed the population UD, migration data were separated to represent spring and fall
elk migrations. I modeled a BBMM migration UD based on all individuals of each season,
separate seasons for male (Appendix A).and female (Figure 3-5 and 3-6), and the degree of
overlap between stopovers for each season and sex (Figure 3-7 and 3-8).
Maps of seasonal comparisons for female elk (Figures 3-5 and 3-6) illustrate potential
differences in habitat use of female elk during spring and fall migrations. Stopovers in the
migration route are represented by green coloration, movement areas in the migration are yellow
shades and pink is an area of low probability of use during migration. The areas of high,
medium-high and medium-low delineate most of the migration route with low use areas between
the other levels of use representing possible direct travel areas. Gaps of low use coloration
between medium use levels should be interpreted as quick movement areas where elk migrated
quickly to the next segment of the migration corridor. The spring route (high use, medium use,
and low use) is more direct and narrow compared to the fall migration which shifts away from
the valley bottoms and roads (Figures 3-5 and 3-6). Stopovers during fall migration appear more
fragmented and smaller in size than the spring migration. A comparison of spring and fall
female BBMM migrations suggest there are three core areas of overlap of stopovers for both
seasons of use, but with a shift away from the main river valley floors (Figure 3-7). Selection of
stopover sites usually did not overlap between male and females (Figure 3-8).
My results indicate there are multiple pathways used by elk to access their summer ranges. I
used a method outlined by Sawyer et al. (2009) where pathways used by >10% of the sampled
population was considered to represent the highest conservation value (Figure 3-9).
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Figure 3-4 BBMM of population migration routes of all male and female Castle-Carbondale elk
from 2007-10
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Figure 3-5 BBMM Carbondale-Castle female elk population of spring migration routes and
stopovers, 2007-2010
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Figure 3-6 BBMM Carbondale-Castle female elk population of fall migration routes and
stopovers, 2007-2010
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Figure 3-7 Comparison of BBMM Carbondale-Castle female elk population stopovers during
spring and fall migration, 2007-2010
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Figure 3-8 Comparison of BBMM Carbondale-Castle female/male elk population stopovers
during spring migration, 2007-2010
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Figure 3-9 Castle-Carbondale elk migration is SW Alberta prioritization of migration pathways
determined using proportional use of the collared population (>10%).
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A number elk used different migration routes between fall and spring (Figure 3-10), but the fall
and spring routes did not differ entirely among years. Ninety-one (91%) of the 33 radio-collared
elk studied for two or more winters portrayed fidelity to the same winter and summer range each
year. A five year old female elk switched from the Castle-Carbondale winter range staying over
in the Crowsnest Pass winter range for one winter and summer, then migrating back to its
original winter range in the Lundbreck Hills the next season. These elk have been called
“switchers” where an individual will migrate one year but not the next, possibly changing
migration strategy based on current conditions (Boyce 1989, Woods 1991). Two elk dispersed to
different winter ranges. Initiation dates of spring migration were variable between individual elk
and between elk in different years. Mean date of the start of migration occurred near the
initiation of calving time periods, April 23 in 2007, (SD = +/- 8.5 days, n = 8), May 6 in 2008
(SD = +/-5 days, n = 26), May 7 in 2009 (SD= +/-3.5 days, n =22), and May 3 in 2010 (SD=+/-
23 days, n =10). As in other published research, the difference in initiation of spring migration
may be related to precipitation and vegetation green-up (Morgantini and Hudson 1989, White et
al. 2010).
Elk migration was distributed along 4 corridors travelling west or east to and from a 146km
2
winter range and a 540km2 summer range spanning 53km north/south along the Continental
Divide from Star Creek southward to the West Castle River valley (Fig. 3.9a). Geographically
there were 4 primary areas of summer range, Star / York Creek, Lynx / Goat Creek, Lost /
Carbondale Creek, and Syncline / West Castle. Elk could be found at elevations of 1200m in the
winter to 1960m in the summer. In 2006 there were 638 elk on the winter range for a density of
4.4 elk/km2.
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Figure 3-9a BBMM Carbondale-Castle female elk population of spring migration routes and
stopovers, 2007-2010.
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Figure 3-10 Castle-Carbondale elk using different spring and fall migration pathways
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DISCUSSION
Elk mortality in study area
Elk in the human-dominated landscape of SW Alberta are exposed to a wide range of human
activities and predators in a spatially complex landscape that may displace them from important
habitat and expose them to increased mortality risks (Muhly et al. 2011, Webb et al. 2011).
Capture related mortalities during the study were low with only one elk loss from the 68 elk
captured. Another single animal died from unknown reasons not related to capture. The elk may
have died of old age, for she was 15 years old. Where elk populations are hunted, hunting is one
of the primary sources of elk mortality (McCorquodale et al. 2003, Unsworth et al. 1993) and
often is much higher than carnivore predation (Allendorf and Hard 2009). The sample size of
Castle-Carbondale elk collared was reduced by 21% due to hunting over four years of study,
compared to 7.5% from natural predators (Table 3-1). Sample sizes for elk harvested by hunters
and by predators were not high, but did reflect a pattern of hunters selecting primarily >2.5 year
old males whereas the predators selected yearlings or females of lower reproductive capability
such as the oldest age classes of females (Atwood et al. 2007, Wright et al. 2006). Alberta
hunting regulations require male elk to have 3 points or more before they can be harvested,
which in SW Alberta usually is an elk > 2 years old.
Elk are influenced spatially by the presence of predators (Gregory et al. 2009) and wolves occur
within defined territories particularly during denning periods where their activities are close to
the den while raising pups (Jedrzejewski et al. 2001, Fryzell and Sinclair 1988, Boyce 1991,
Creel 2002). Elk migrating to the Castle drainage could encounter an active wolf den during
migration. Rarely were elk GPS locations documented within five kilometers of the active den
site. Wolf presence may have motivated the female elk in particular to move through the area in
a quick and direct fashion to their summer ranges. Two elk died during migration as a result of
wolf predation, although not near the wolf den. The wolf territory encompassed the entire elk
home range and overlapped with cattle grazing areas (Moorehouse and Boyce 2011). The influx
of summer livestock grazing and initiation of migration by elk may result in a replacement of
cattle for elk as prey (Garrot et al. 2005, Moorehouse 2010). This is further complicated by wolf
use of boneyards, areas used by ranchers to dispose of dead cattle during the year (Moorehouse
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and Boyce 2011). This could reduce predation pressure on elk during summer and fall when
cattle and elk are grazing on public land and private land.
One method for elk to avoid predation is to migrate; as suggested by the predation risk avoidance
hypothesis (Mysterud et al. 2012). Predation may be an important driver for migration
(Hebblewhite and Merrill 2007). Calves are more prone to predation and migration may be a
means to avoid areas of high predation risk. It may also be best to live in solitude during calving
season (Bergerud et al. 1984, Creel et al. 2005) to reduce the possibility of being detected by
predators. There are grizzly bears, black bears, cougars, and coyotes that could prey upon elk
neonates in SW Alberta. The extent of predation from most species is not known, except for the
cougar which rarely preyed upon elk during 2 years of study (Banfield 2012). No collared elk
during this study period died during winter, which can be a stressful and vulnerable time for elk.
Migration Metrics
Migration distance for the Castle-Carbondale elk was from 5- 34 km per seasonal migration
(Table 3.3). The timing of spring migration did not vary annually. Most spring migrations
starting the first week of May and ending the first week of June. Fall migration showed greater
variability possibly due to hunting pressure and differences in occurrence of snowfall events. As
in other published research, the difference in initiation of spring migration may be related to
precipitation and vegetation green-up (Morgantini and Hudson 1989, White et al. 2010).
Movements of elk during the Castle-Carbondale herd migration were meandering with a slow
rate of movement, (a defining characteristic of stopovers), interspersed with rapid migration
movements between stopovers. Migration took from two to 65 days to travel a maximum linear
distance of 34 km, indicating some elk spent a considerable portion of their migration time on
the migration routes, while others moved quickly through. The mean of spring migrations was
20 days (SE +/-1.5, n=68) with those taking longer possibly calving on the transitions ranges and
staying there until the young were more mobile. Longer time periods in stopovers and increased
movements during mid-May to June were considered to be distinctive of female elk calving in
Yellowstone National Park (Vore and Schmidt 2001). Fall migration had a mean duration of 21
days (SE +/-2, n= 61). Migration duration of Castle-Carbondale elk were variable possibly
reflecting individual behavioural response to environmental and human disturbance conditions.
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This contrasts from the quick few day migration events documented of bighorn sheep in B.C.
(Dibbs 2007), the quick migration strategy of mule deer reported by Sawyer et al (2009) and the
7 day migration of an elk herd in Yellowstone (White et al. 2010). A second elk herd summering
in Yellowstone National Park and wintered in an area open to hunting outside of the park
averaged 43 days to complete fall migration. This delay to the winter range was likely to avoid
hunting risk (White et al. 2010). These results are similar to Castle-Carbondale elk that display a
flexible strategy to reduce hunting pressure by moving short distances in the fall to avoid hunters
and moving slowly in the spring to take advantage or nutrient rich forage (Ciuti et al. 2012,
Hebblewhite and Merrill 2009).
Ninety-five percent of the Castle-Carbondale herd migrates suggesting migration is beneficial to
elk. Since they are a mountain elk population they can follow green-up of vegetation from lower
winter range to high elevation summer ranges. The forage maturation hypothesis best explains
upward migration due to plant phenology (Fryxell and Sinclair 1988, Hebblewhite et al. 2008,
Mysterud et al. 2011). Early phenological plant stages are higher quality forage than mature
plants. By following snowmelt and the elevational gradient of green-up, migrators are able to
feed on higher quality plants for a longer duration than if they stayed at lower elevations
typically found on winter ranges (Hebblewhite et al. 2008, Mysterud et al. 2012). Migrating
Castle-Carbondale travel through montane habitats of topographical and plant diversity, which
should extend the duration of new growing forage availability to elk. Southern aspects would be
the first to green-up, with later access to north facing snow melt where low temperatures can
prevail, result in delayed plant growth and enhanced digestibility (Hebblewhite et al. 2008,
Mysterud et al. 2012). The slow rate of travel documented during elk spring migration could also
be supported by the forage maturation hypothesis as elk move gradually to their summer range,
taking advantage of the new growth of vegetation at varying elevations and aspects (Mysterud et
al. 2012).
Population Migration
My study uses BBMM a utilization distribution model to spatially depict the extent of elk
migration routes in a landscape of SW Alberta where increasing amounts of human activity are
concentrated along roadways and trails throughout the landscape. I hypothesized due to the
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modest distance between summer and winter ranges and the extent of human disturbance in the
area (Muhly et al. 2011), the migrating portion of the Castle-Carbondale elk herd would travel
quickly through transitional ranges and not stopover on route to the destination seasonal range.
Using a population-level BBMM I identified a network of migratory corridors with stopovers
connecting winter and summer ranges, thus failing to support my hypothesis.
Using the BBMM to model elk migration appears to be a useful method for identifying
population-level pathways including stopover areas and areas of rapid migration movements to
seasonal ranges (Figure 3-4). Migration routes were used consistently during each year of study
as indicated by the repeated use of stopover sites and migration travel areas which are
determined by the BBMM process (Fig 3-4). In fact, a number of Castle-Carbondale elk used
the segments of migration route multiple times during their time on the transitional range, during
either spring or fall migration seasons and occasionally in the summer. A migration study in
Banff National Park, in an area with no hunting, also found some elk in the Bow Valley
population moving back and forth between winter and summer ranges multiple times (Woods
1991). Males summering at high elevation ranges will move towards or to lower elevation
winter ranges to increase their chances of finding females during the rutting period (Woods
1991). Response to environmental changes may be a partial explanation for the back and forth
movements of some elk in my study. In the spring a few elk would start migration in mid-April
but would return to the winter range after a deep late spring snowfall. In Africa, Serengeti
wildebeest have been observed reversing direction and returned to previously vacated areas when
temporary periods of drought interrupt the usual onset of the rainy season (Pennycuick 1975).
These movement patterns illustrate the importance of migration corridors or segments of the
route; not only for travel during migration to seasonal ranges, but also as an alternate route away
from snow covered areas, calving sites and possibly escape from hunting pressure or predators.
To assess if migratory corridors differed between seasons I compared BBMM maps of spring
and fall elk migration. There was a notable shift in many stopovers to areas not used during the
spring, although two of the larger area stopovers were both used during the fall and spring by elk
(Figure 3-7). Possibly a change in stopover use and return to a few of the spring stopovers may
be related to a need for secure areas during the hunting season (Cole et al. 1997, Millspaugh, et
al. 2000, Rumble et al. 2005).
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Radio-collared adult female elk showed fidelity to travel routes and a return to the same summer
and winter ranges in successive years. The Castle-Carbondale herd exhibited fidelity to the same
topographical features used as core stopover areas during four years of study. Elk would
stopover in the Carbondale-Lynx Creek foothills complex near the junction of three streams,
Castle River, Carbondale River and Lynx Creek during spring and fall migration. From this
topographic complex the elk on spring migration split into three different routes traveling to
separate summer ranges in three different watersheds across a broad summer range along the
Rocky Mountains (Figure 3-4My study supported the results of recent studies (White et al. 2007,
Sawyer et al. 2009) suggesting temperate ungulates use a multiple-route migration strategy to
migrate from a small winter range to a large summer range. Conservation of multiple routes is
more complicated than one route because the increased possibility of developments and human
activity will overlap the corridors. A population level analysis of elk migration (Fig. 3-9) depicts
the priority migration areas for conservation of Castle-Carbondale elk migration. The high
priority polygons delineate areas where elk migration would benefit from management
guidelines to balance the conservation of movement areas between elk and human use. The
current analysis (Fig. 3-9) considers both spring and fall migration to identify the high priority
areas. This analysis illustrates the main migration moves along the lower Castle River to
Carbondale Hill, Maverick Hill and Cherry Hill, separating into smaller corridors into the
summer ranges.
This confirms a portion of Morgantini’s results (unpublished data) during his telemetry elk study
(1989- 92). He documented Castle-Carbondale elk separating into two subareas while on the
summer ranges. A fourth route is used by a smaller proportion of the Castle-Carbondale herd to
migrate from the northeastern segment of the winter range west to the Crowsnest River drainage.
These migration movements and the ones migrating to the West Castle valley are similar to a
traditional pattern of migration movement, where elk moved longer distances between stopover
areas, as described by Sawyer et al. (2009). Individual migration pathways along the Carbondale
River and to the Goat Creek drainage were different migrations, shorter in length but spending
more time in a lower number of stopovers. These findings indicate a high percentage of Castle-
Carbondale elk show fidelity to seasonal migration routes and seasonal ranges which may be
advantageous to elk for it provides knowledge of seasonal resource availability (Wolf et al.
2009).
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Spring and Fall Population Migration
My results, both at the individual and population scale, were different from other studies using
BBMM (Sawyer et al, 2009, White et al. 2010). Instead of short stopovers of a few days
followed by extended quick movements of travel towards the seasonal range destination, 32% of
the elk in my study area displayed behaviour of staying an extended time period in stopovers
within the migration route, gradually moving towards the summer range. The Castle-Carbondale
herd exhibited high variability in its migration movements. Particularly in the spring, many of
the individuals staying at stopovers for an extended time were utilizing the 17,765 ha area burned
in the 2003 Lost Creek Fire. The segment of the Castle-Carbondale herd traveling along the
Crowsnest drainage displayed a different movement strategy; one of shorter time periods spent in
smaller stopover areas with longer segments of migration movement to the summer range. This
herd does not travel through the Lost Creek burn site on route to summer range. A similar
behaviour occurred in the fall during migration from summer range; individual elk would move
part or all of the way to the winter range, then quickly and abruptly move back to the summer
range. I hypothesize these actions could be a response to hunting activity which occurs from the
first week of September until December 20 of each year or were movements to rutting areas
(September – mid October). At other times elk would stay in one general location (stopover) for
a few days, apparently secure from hunting pressure and other potential disturbances.
Castle-Carbondale elk displayed a number of movement patterns after splitting up into three sub-
herds. In my study, elk moving through the Lost Creek fire burn of 2003 were more likely to
stopover for a longer duration, possibly feeding on the new forbs and grasses found in the burn
site. Elk traveling farther south into the Castle and south Carbondale areas moved more quickly
and directly. Possibly there was less food available in the forested landscape and there was an
active wolf den between the stopover hub and their summer range.
Migration Characteristics of Different Sexes
Separating male elk and female elk migrations from the population BBMM, I found the male elk
appear to be using the transition range differently than the female elk (Figures 3-3 and 3-4).
Male and female elk are known to spatially segregate themselves for time periods with the males
possibly searching for the rich food supplies and willing to risk security for growing body mass
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and antlers important for the rut (Geist 2002). Sexes may be segregated, but still use the same
habitats and areas at different times of the year. There are examples of males and females using
different habitats and areas outside the mating season resulting in seasonal movements between
different areas (Ruckstuhl and Neuhaus 2005).
The various possible causes for sexual segregation continue to be debated. Females are expected
to use more areas of security in an attempt to provide security for the calf at a cost of lower
forage quality (Geist 2002). These responses could reflect sexual segregation with regard to
resource utilization (Bleich et al. 1997, Main et al. 2008). Two possible ecological hypotheses
are suggested for segregation in ungulates: forage-selection hypothesis (FSHs) and reproductive-
strategy hypothesis (RSHs) (Gregory et al. 2009). FSHs predicts male and female use habitat
differently in regards to food availability due to allometrically differences of body size no matter
what the level of predation risk may be (Ruckstuhl and Neuhaus 2002). RSHs or predation-risk
hypotheses suggests sexual segregation is a matter of different methods of survival tactics
between males and females (Main 2008). However, the ecological significance of sex
segregation between male and female elk may vary depending on scale. Sexual segregation may
occur at the habitat spatial scale driven by reduction in predation risk (RSHs hypothesis), while
differences in forage selection (FSH hypothesis) may explain segregation at the habitat-patch
scale (Gregory et al. 2009).
From a management perspective, sexual segregation in the Castle-Carbondale herd poses a
challenge. A multi-branched antler harvest criteria is in effect allowing for harvesting males of
all age classes over two years of age. Female elk are managed using a draw system with limited
tags being allotted each year. Male elk in the Castle-Carbondale are exposed to extensive
hunting pressure starting early September until the last week of November. Hunting occurs in
the public lands management area, an area occupied by elk during the summer, fall breeding
season, a portion of the winter and during migration. If the sexes are spatially segregated over a
large landscape there may be difficulties managing for both sexes. If males migrate through two
management areas with two different hunting seasons, males may be overharvested because they
are probably hunted in both the rutting areas (early season) and wintering range (late season)
(Sibbald et al.2001). Elk management strategies could benefit by considering sexual segregation
and migration during the hunting periods.
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Yearling Male Elk Migration and Dispersal
Research suggests the mechanism of dispersal in animal populations has evolved to circumvent
or lessen the probability of inbreeding depression and facilitates movements of individual
animals from crowded ranges with concentrated competition (Martins et al. 2002). Vacant
suitable habitat can be colonized or re-colonized by dispersing animals allowing for expansion of
populations (Singer et al. 2000, Woodroffe 2003). Dispersal is commonly a characteristic of
young animals and this was the case in my study. Male elk ≤2 years were the only elk to disperse
in the Castle-Carbondale herd and other herds in SW Alberta.
Relocation data for male elk was entirely representative of elk <2 years old, a time period when
their movements can be widespread and in some cases result in dispersal (Petersburg et al. 2000).
A review of sex based dispersal (Greenwood 1980) suggested dispersal was female biased in
most birds and male biased in a majority of the mammals. This may be related to different
mating strategies where male birds defend territories (resources) and in mammals, males defend
females. Males have the potential to increase individual reproduction by breeding with multiple
females which according to the male – competition hypothesis, males should disperse as they
reach sexual maturity because they are often unlikely to mate in their natal area (Dobson 1982).
This suggests dispersal in polygamous ungulates such as elk would probably be male biased
(Greenwood 1980, Martins et al. 2002). Female biased migration has been documented in one
year old elk (Boyce 1989), although partial migration populations have had very little study. My
study of female elk (1-18 yr.) and males less than 4 years appears to support the male-
competition hypothesis.
I documented dispersals of yearling male elk to BC and Montana from the Castle - Carbondale
herd (n = 2) and other herds (n = 2) in the population, suggesting yearling elk are the primary
means of maintaining genetic diversity in this population. Dispersal of male elk from the Castle-
Carbondale herd occurred on two occasions with both elk using the full extent of the population
migration route to access their new home range. Switching occurred in one individual, a female
which dispersed to the Crowsnest herd winter range, summered in the same area and the next
winter travelled back to her original Castle – Carbondale winter range. Her movements, similar
to the male dispersals occurred along migration pathways used by migrating Castle – Carbondale
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elk while within the herd home range. This suggests that conserving migration corridors may
also be valuable for elk dispersal and migration. Of the two elk dispersing, all survived on a new
winter range. An additional 2 male yearling elk displayed exploratory movement behaviour
where they stopped on summer range, then traveled 60+ km straight line distance westward over
the Rocky Mountains moving through the Flathead Valley for about a month. One of the male
elk went as far west as Fernie, BC before heading east, back to Alberta. In early July they both
came back to a summer range used by other elk from the herd and ultimately migrated back to
their natal winter range
Impact of Wildlife Land Use Management
Population utilization distribution of migration based on the BBMM illustrated that elk in this
region have a strong fidelity to winter range, summer range and migration routes although for
some elk the fall migration route differs from the spring (Fig.3-9a). In a number of cases a new
route was selected during the fall hunting season (Figures 3-6 and 3-11). Hunting is an obvious
disturbance to elk, yet many other human created disturbances have similar effects (Friar et al.
2008, Morgantini and Hudson 1985, Rumbleet al. 2005). Researchers have documented
disturbance to elk creates a change in habitat use and diet (Edge and Marcum 1985), altered
migration timing (Kuck et al. 1985), caused avoidance of roads (Rowland et al. 2004), avoidance
of human activity (Wisdom et al. 2004), increased vigilance (Childress and Young 2003), created
a negative physiological response (Millspaugh et al. 2001) and increased movements associated
to human disturbance (Cole et al. 1997, Rumble et al. 2005) of elk. This evidence could be used
by wildlife managers to justify conserving migration routes. The BBMM represents the present
and possibly the last few decades of movement patterns of elk migration for the Castle-
Carbondale herd as migration pathways are passed from mother to calves (Barber-Meyer et al.
2008). My results may be used as a baseline to quantitatively track any future changes in elk
migration patterns (White et al. 2010) or changes in the number of elk migrating. In other areas,
it has been suggested a reduction over years in the number of elk migrating may be linked to
anthropogenic disturbance, habitat improvements and increased predation risk during migration
or a combination of circumstances (Boyce 1991, Hebblewhite et al. 2006, Hebblewhite and
Merrill 2011).
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I have delineated elk migration routes and areas of importance to elk called stopovers that are
expected to be important for increasing body condition and for some females, calving areas
(Sawyer 2009). These results can be used to identify environments where potential development
may occur with the least negative impact to elk migration. Important areas such as stopovers
should be managed for conservation of migration routes. Resource managers looking to improve
elk habitat may be able to use my results to identify management actions that could enhance elk
habitat (restoration by selective logging or burning) on the transitional ranges. Future research
investigating the connectivity of the migration routes would be an important component to
conserving elk migration routes and other animals using the same areas for travel. Research on
elk habitat requirements at a habitat and landscape scale during migration would provide
perspective regarding the suitability of the land base between seasonal ranges to provide
alternative options for migration pathways to change if the existing traditional route is blocked or
severely compromised.
CONCLUSION
Migration Route Modeling
An essential aspect of maintaining and conserving migration corridors is to know where they are
and why elk use the certain areas. Elk migration pathways were not spatially delineated for the
Castle-Carbondale herd until this research was completed. Morgantini (1995) and others have
described possible routes based on very high frequency (VHF) telemetry, anecdotal observations
and historic records of Waterton Park wardens (Sheppard 1992). After four years of study
tracking 38 female and 12 male elk with a total of 138 spring and fall migrations, we have a
clearer understanding of the migration corridors used by the Castle-Carbondale herd.
Using the BBMM to calculate UD of migration I was able to model elk movements during
migration events, with elk moving quickly between patches of habitat (stopovers) assumed to be
important for foraging, resting and security. The distance of migration was modest with most elk
moving through the transitional range within 20 days. Slow movement during spring is possibly
due to the use of rich vegetation as forage in the migration corridors green-up. This would
provide time for snow depths at higher elevation to recede and still provide elk with rich foods to
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help replenish their body condition after the winter months. Some elk are known to stop for
calving while migrating through the transitional range before getting to summer range.
Challenges of Elk Migration
Migrating elk (n=50) comprise 95% of the collared animals found in the Castle-Carbondale herd.
They travel 10 – 34 km from the winter ranges to high elevation mountain summer ranges,
passing through montane forest to subalpine and alpine meadows, with some stopping over in a
six year old 17,765 ha burn. Direct and indirect human effects on the habitat resources in the
study area can be high (Muhly 2010). Such impacts by humans need to be understood in areas
such as SW Alberta (Arc Wildlife Services Ltd. 2004) where demand for natural resources and
recreation is increasing (Naylor et al. 2009, Muhly 2010). To survive and produce young,
ungulates must have options to select habitat with sufficient resources while reducing predation
risk (Festa-Bianchet 1988, Houston et al. 1993). Humans influence wildlife distribution and
fitness directly through activities such as recreation and disturbance from development (Fraire et
al. 2008, Fryzell et al. 2010, Muhly 2010, Stankowich 2008) and by improving resources through
agriculture or reducing predators (Muhly 2010). Migratory routes of adequate connectivity are
required by the Castle-Carbondale elk to maintain migratory behaviour from winter to summer
ranges. The continued existence of this partially migratory herd depends on being able to take
advantage of high quality habitats on summer ranges.
Elk have the widest geographic distribution of any wild ungulate in the world (Clutton-Brock et
al. 1982) and exhibit a diverse range of movement behaviours such as migration, residency,
partial migration and dispersal (Adams 1982, Boyce 1991). Elk with home ranges in the
mountains often undertake altitudinal migrations following vegetation changes over reasonably
short distances. The species ability to adapt to the many environmental changes is one of the
reasons they are widely distributed with increasing populations in many areas. A number of
researchers have noted the elk’s flexibility in movement patterns and how it allows them to
adjust to a changing environment (Boyce 1991, Geist 1982, Morgantini 1988). Plasticity of elk
can be high, although one main theme continues to be noted in studies over the last decade. It is
displacement of elk from areas of human traffic, development and activity typically within 500 –
1000m. Such displacements have the potential to reduce the area of critical ranges available to
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elk. This continuous loss of effective habitat may be the greatest challenge for maintaining elk
migration and populations.
With 93% of elk from the Castle-Carbondale herd migrating, this research will be useful in
managing the elk population. Knowing migration corridors of elk and important stopover areas
will enhance wildlife managers’ ability to maintain the movements of migratory elk. The
BBMM results may be useful in managing the impacts of human activities temporally and
spatially on the migration route.
The quantitative framework I used (Sawyer et al. 2009) models migration routes for both
individuals and at a population scale. It delineates the Castle-Carbondale elk migration route
providing options to plan developments be it roads or well sites in a way to conserve the core
areas of migration. My results also support Sawyer et al. (2009) conclusions where movement
and stopover areas may be distinguished based on different behavioural states; similar to others
using non-linear curve fitting (Johnson et al. 2002), state-space models (Forester et al. 2007),
Markov models (Franke et al. 2004), random walks (Morales et al. 2004) and first passage
methods (Bailey and Thompson 2006). I found similar characterizations of movement routes as
Sawyer (2010) did with mule deer, where elk displayed movement patterns of slow moving over
an extended time period followed by quick movements through corridors to a new stopover.
This differentiation between movements may be a useful management opportunity, since my
modeling found that the elk population favoured some areas over others. These areas could be
targeted for conservation as well as habitat enhancement opportunities.
Stopovers in the Sawyer study (2010) had higher forage quality compared to movement corridors
connected to them, forage quality improved as elevation and distance from winter range
increased. This would fit the strategy of migratory ungulates to follow the green-up of the most
nutritious vegetation to maximize energy intake during the growing season (Albon and Langvatn
1992, Fryzell et al. 2004, Holdo et al. 2009). In my study many of the stopovers were located in
a 2003 burn where forbs and grasses would green-up quickly, providing rich forage for elk
(White et al. 1998). Two other migration routes not passing through the burn had fewer stopover
sites of a smaller area than elk which passed through the burned area, possibly because elk using
the burn were inclined to stay in areas of very rich nutritional forage for extended time periods.
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The BBMM analyses highlighted an important stopover at the junction of Castle and Carbondale
Rivers, located near the western boundaries of elk winter range. Elk are regularly observed here
in the spring, feeding in the large meadows surrounded by aspen where some of the first green
grass sprouts can be found (Paton 2005). From this topographic hub, the female elk select one of
three routes traveling westward along three drainages to different summer ranges. This stopover
within the winter range appears to be an important one for it is an area providing new spring
forage as elk migrate through the winter range. The combination of winter range and a migration
corridor / stopover in one area suggests it is very important for spring movement of elk to the
summer ranges and should be considered critical elk habitat. In this chapter I used the BBMM to
determine stopover sites and movement corridors along the migration route of the Castle-
Carbondale elk herd. I visually reviewed and compared BBMM for differences between sexes,
migration seasons and for all elk and both migration seasons at once. There appears to be
differences in use between stopover by female elk during spring and fall migrations time periods.
In Chapter Four, I develop a spring and fall resource selection function (RSF) for female elk
migration pathways to understand their patterns of selection for a migration route and possible
differences between spring and fall migration.
My study provides regional wildlife managers with quantitative data of migration corridors to
manage potential future land use activities which may impact elk use of migration routes and
eventually population dynamics and distribution. Migration events are important for they
provide a means for greater numbers of elk to meet their life history requirements by increasing
available range beyond wintering areas, enhancing their fitness and reducing negative grazing
affects to winter ranges (Knight 1970, Rogala et al. 2011, Walter et al. 2010). Conservation of
migration corridors has the potential to facilitate elk to continue to migrate thus reducing the
likelihood of elk home ranges being limited to year round use of the migratory elk winter range.
Increased elk use of habitat on the winter range will invariably increase depredation events
causing increased complaints from private land owners. This may result in social pressure to
reduce the numbers of an elk population managed by an arbitrary number rather than ecological
considerations. From an ecological perspective large mammals such as elk are keystone species
that affect ecosystem processes such as nutrient flows, nutrient cycling, and successional
trajectories of plant communities (Kie et al. 2003). The potential losses of keystone species on
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portions of the landscape are not well known indicating a cautionary approach of conserving
migration is required.
Research Issues
My study design of maximizing sample units by removing and replacing collars on different elk
after two years of tracking was useful in providing a larger sample size of elk and a broader
understanding of elk migration. Location fixes of two hours and a location error of <20m
provided a large number of accurate relocation fixes enabling modeling to portray elk migration
UD. These temporal and spatial attributes of the study provide data of an appropriate scale
useful for my research to characterize migration travel and stopover areas.
A common short-fall of migration studies is the length of time and variety of environmental
conditions they represent due to changing conditions between years. A majority of migration
studies are only one or two years and they usually do not reflect animal response to varying
environmental conditions such as weather over time. With four years of study I was able to
include a wider range of environmental conditions possibly providing a clearer picture of elk
migration over time.
Collar reliability and the drop off mechanisms were at times a concern, particularly during the
first year. I had a number of collars stop working, drop off prematurely or not drop off at all,
reducing the final number of sample units. Fortunately my study collared numerous animals,
providing a large sample size to use in analyses. Migration studies are further complicated by
the trait of migrating animals tending to move very quickly through forested or rugged terrain
between stopovers where it is difficult to acquire GPS relocations. Collection of two hour fixes
worked well in this study with 93% of location fixes successful during migration. One limiting
factor of a study of this magnitude is the cost of undertaking it. Collars and helicopters are
expensive, so without the financial support of many organizations I would not have been able to
succeed in achieving such a high level of data quality or volume.
Argos / GPS technology collars on male elk were an important component of the success of this
study. Tracking yearling elk across mountainous terrain is no easy task. They can move large
distances over a short time period and keeping track of some of the male locations would have
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been impossible. Data fixes of the elk were sent from the collars to Argos satellites orbiting the
earth, to a central data receiving facility in the USA where it was forwarded to the researcher’s
computer. Once a week the locations for male elk were updated, enabling us to efficiently track
their travels remotely. This technology was not foolproof because collar failure resulted in a loss
of potential data. Collaring yearling male elk from a hunted population of elk also reduced the
amount of data I was able to collect of elk movements because a high percentage of males were
harvested by hunters. Although, loss of these individuals did not provide insights into elk
migrations; if they were shot in the first year, it did provide insights into human caused mortality
and population demographics.
GPS technology has improved, enhancing my ability to study ungulates by providing increased
frequency and accuracy of relocation points, but the methods to analyze movement data are
limited. It is limited by the abilities of modeling to account for uncertainty in animal movements
between known locations (Horne et al. 2007, Sawyer et al. 2009) and it is difficult to scale
individual migration data to population level routes. Until recently, migration was investigated
by connecting successive GPS location points of collared animals (Berger et al. 2006) which
provided metrics such as timing, distances travelled and movement rates of migration. The draw
back from such methods are that there is no defined area of route utilization based on error, thus
we would not know if the route is 10m or 1km wide (Sawyer 2010). The BBMM used in my
study was able to model the areas of route utilization.
Management Recommendations and Future Research
1. Conserve stopover sites; particularly those that may be used for calving.
2. Make all efforts to plan new development outside of migration route core areas.
3. Maintaining elk migration by conserving conn ectivity along the migration routes will
help to circumvent possible conflicts between private land owners and elk populations on
winter and migration ranges.
4. Implement land management plans which conser ve areas of winter range and migration
routes by putting private land into conservation easements or have critical habitat status
on public land would be beneficial to elk and other species using the area.
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5. Game management plans for elk should consider the potential of overharvesting of males
that migrate through two wildlife management units during the rutting season and on to
the winter range.
6. Reducing and managing roads and road densities particularly within core areas of winter
and summer range, control new road devel opments within 300m to 1000m of migration
corridors, depending on topography and forest cover. Gating roads can be one tool to
achieve this goal.
7. Use prescribed burning or selective tree ha rvesting techniques to maintain stopovers
vegetative conditions or crea te new stopover sites along mi gration routes with few
stopover sties due to a closed canopy of trees.
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APPENDIX A - ELK MIGRATION
Figure A-9 BBMM population utilization distributions for combined fall male and female elk,
2007-2010
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Figure A-10 Spring utilization distribution of all elk migrations from 2007-2010
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Figure A-11 Fall population utilization distribution of all male elk migrations from 2007-2010
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Figure A-12 Spring utilization distribution of male elk migrations from 2007-2010
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Figure A-13 Fall utilization distribution of male elk migrations from 2007-2010
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CHAPTER FOUR: ELK STOP-OVER AREAS
ABSTRACT
Stopover ecology, well known in avian ecology, has recently been shown to be a strategy of
ungulate migrants in temperate regions. I used fine-scale global positioning systems (GPS)
migration data and logistic regression to quantify stopover characteristics for seasonal migrations
of elk in the Rocky Mountains of Alberta. Elk completed migrations up to 34km in 2 to 65 days.
Using logistic regression to compare elk GPS locations with random points within the elk herd
home range I found elk avoided roads by a mean of 525 m, used areas of lower canopy, lower
slopes, and higher terrain ruggedness. Avoidance of roads appeared to be more important to elk
than avoiding known wolf habitat. I hypothesize stopovers have an strategic role in this
migration providing access to rich nutritional forage in the spring and increased security for elk
during the fall migrations which coincides with hunting season.
INTRODUCTION
Migration is an event undertaken by a wide range of species to access areas of additional nutrient
rich forage and meet energetic requirements on their way to traditional breeding or summering
ranges. For some species such as ungulates in heterogeneous mountain landscapes, migration
enables them to maximize the availability of high quality habitats required to complete their
annual life cycles (Morgantini and Hudson 1989, Boyce 1991, Mysterud et al. 2011).
The primary limiting factor in many migrating animals is the energetic requirements needed to
finish migration, particularly bird species. To complete migrations, especially long distance,
animals may use a strategy of pausing to feed in habitat patches called stopovers. These are
found along the migration pathway and provide rich food sources and a place to rest and
replenish energy reserves (Mara et al. 2005). Avian migration and stopover strategies have been
studied for decades (Alerstam et al. 2003). Maximizing fitness is a priority of all species
therefore the strategy of birds using stopovers may help researchers understand the strategies of
ungulates stopover use. However, our knowledge of migrating ungulate stopovers is very
limited. Only recently, has research investigated if stopovers also used by ungulates
(Hedenstrom 2008, Sawyer and Kaufman 2011). Understanding the metrics of stopover
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locations and habitat characteristics may add to our understanding of life histories, population
dynamics (Salewski and Schaub 2007), and the development of conservation plans (Shimzaki et
al. 2004) of migratory ungulates.
Avian migration strategy can be based on quick movements with stopovers to refuel along the
journey because their relatively small body size reduces their ability to carry large fuel loads
(Akesson and Hedenstrom 2007). Some avian individuals fly non-stop during their migrations
while others pause at stopover sites (Chevallier et al. 2010). An optimal stopover site should
provide access to food, water and security cover so species can restore energy expended during
the preceding migration activity and replenish energy reserves for the remaining trip (Hutto
1998, Morris et al. 1996). Many ungulates migrations are different than most bird migrations.
Temperate ungulates could complete a typical migration (20 -150km) quickly since they are able
to travel 20 – 50 km in a day. However, such a strategy may not provide fitness benefits
(Sawyer and Kauffman 2011). In ungulates, maximizing nutrition and improving body condition
to enhance fitness is known to be a high priority (Cook et al. 2004, Parker et al. 2009, Sawyer
and Kaufman 2011). Rather than migrating quickly, ungulates appear to use the strategy of slow
migration movements while maximizing foraging of high quality foods (Hebblewhite et al. 2008,
Sawyer et al. 2009, Sawyer and Kaufman 2011). Maximum energy inputs occur when plants are
less mature and highly digestible (Hebblewhite et al. 2008). After elk survive winter they must
consume nutrient rich vegetation to maximize fitness while reducing predation risk from both
human and native predators. Completing migration as a quickly as possible as observed in birds
does not seem to have any obvious fitness benefits for ungulates. Understanding stopovers
characteristics during elk migration could assist in the development of new conservation
strategies for migrating ungulates (Sawyer et al. 2009).
OBJECTIVES
I used fine scale elk movement data from GPS collars to determine stopover areas in Chapter
Three. Why elk stop and use these areas is not well known. The objectives for my study were
developed to determine characteristics of the stopovers used by elk during migration. The
predictions of my study were elk would: 1) use stopovers removed from roads; 2) canopy closure
would be greater than 50% and less than 80% to provide forage and security cover; 3) elevation
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would be near valley bottoms, particularly in the spring when elk hunting does not occur and
few people are in the area; 4) terrain ruggedness would be modest to make travel easy thus
limiting energy expenditure; and 5) elk would reduce use of areas used by wolves.
STUDY AREA
The Castle-Carbondale study area encompasses approximately 1000 km2 in southwest Alberta.
It represents a large component of an internationally recognized area known as the Castle Crown
of the Continent (Figure 4-1). Alberta Sustainable Resource Development administers 100% of
the public forest reserve. On the eastern boundary of the provincial forest reserve are private
ranchlands intermixed with cropland. The study area includes portions of two municipal districts
(M.D. Pincher Creek, Municipality of Crowsnest Pass). Livestock grazing occurs seasonally on
public land and year-round on private land. Industrial activities in the area include forestry and
natural gas extraction. Human activity on the landscape is widely distributed, comprised of
random camping, off-road vehicles, mountain biking, hiking, hunting, and fishing combined with
winter activities of snowmobiling and skiing.
Elevations range from 1250 to 2330 meters. The four kilometre wide strip of private land on the
eastern boundary represents a transition zone between grassland and montane, continuing
westward along montane foothills, which quickly rise to subalpine and alpine environments of
high elevation mountains along the Continental Divide between Alberta and British Columbia,
Canada. The area is composed of two natural regions and three natural subregions. The Rocky
Mountain natural region is comprised of the Montane and Subalpine subregions and the
Grassland natural region includes the Foothills Fescue subregion.
Environmental characteristics of the Rocky Mountain natural region include cool summers (13.9
Celsius), short growing season, high annual precipitation (798 mm) and the highest snow loads
found in Alberta (Downing and Pettapiece 2006). The landscape is shaped by the prevailing
Chinook winds which create snow-free southwest facing slopes exposing winter grass and shrub
forage for ungulates. Montane and Subalpine subregions consist of rugged terrain with
elevations from 825m to 2,300m. Dominant vegetation is lodgepole pine (Pinus contorta)
Douglas fir (Pseudotsuga menziesii), aspen (Populus tremuloides), subalpine fir (Abies
lasiocarpa) interspersed with grassland slopes, meadows, wetland complexes (Downing and
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Pettapiece 2006) and clearcuts. The Foothills Fescue subregion typically is rolling hills
(elevation 800 m to 1,525 m) dominated by mountain rough fescue (Festuca campestris),
bluebunch fescue (Festuca idahoensis) and Parry’s oatgrass (Danthonia parryi). Portions of the
subregion in the eastern part of the study area have been converted to cropland or tame pasture
grass species.
Figure 4-1 Study area for Castle-Carbondale elk, 2007 – 2010. (location 694298 E 5483627 N)
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MATERIALS AND METHODS
Capture, Collaring, and Data Collection
My project used a helicopter and net-gun to capture 39 female elk and 14 male elk on the winter
ranges of southwestern Alberta from January to March during 2007-2010 (University of Alberta
[Edmonton, Alberta, Canada] Animal Care Protocol number 353112). Elk were blindfolded and
hobbled to allow collaring and sampling with low impact to the elk. Elk were fitted with Lotek
4400M GPS, 4400 GPS / Argos collars (Lotek,Newmark Ontario, Canada) and GEN4-GPS
(Telonics, Mesa Arizona) equipped with mortality sensors that increased pulse rate if the collar
remained motionless for >6 hours. GPS units were programmed to obtain location fixes every
two hours (i.e. 12 per day). We located radio-collared elk from access roads at least once a
month and some herds such as the Castle-Carbondale every week to confirm location and status
of the elk. Collars from elk that died were refitted on new elk. The collars were outfitted with a
remote drop off device programmed to disengage after 104 weeks. When the device failed elk
were recaptured by the helicopter with net-gun method to retrieve the collars.
Identifying Migratory Elk
Elk populations such as the Castle-Carbondale herd are partially migratory, where one segment
of a population undertakes seasonal migration while the other remains on a single range
(Hebblewhite 2006, Lundberg 1988). Within a population of elk there may be a number of
different phenotypes (Boyce 1991). In the partially migratory Carbondale-Castle herd there are
migratory, resident and dispersal phenotypes. I assigned phenotypes as defined by Boyce
(1991). Elk with seasonal home ranges overlapping entirely or predominantly are defined as
resident elk. Migratory elk will move from a winter range to a separate summer range and return
to the same winter range, whereas dispersing elk will leave the winter range to another separate
seasonal range, not returning to the original winter range. Random sampling of animals was
attempted (Otis and White 1999) by directing helicopter capture crews to collar individuals from
different groups of elk located across the entire extent of a herd’s winter range. To maximize
sampling intensity we chose to collect two hour location fixes with the collar dropping off after
two years, the collar was later redeployed on a different elk. To control location error of data
used for analyses, data were sorted to select all relocations with three-dimensional (3D) and two-
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dimensional (2D) values with a dilution of precision value <8 (Adrados et al. 2003, D’eon et al.
2005, Pepin et al. 2008, Rempel and Rodgers 1997).
From 2007 – 2010, 68 elk were collared; 19 elk in 2007, 24 elk in 2008, 12 elk in 2009, 13 elk in
2010. Data were imported into ArcGIS 9.2 (Environmental Systems Research Institute, Inc.
Redlands, California, USA). To reflect seasonality of stopover use I separated elk migration data
into two migration events: spring migration and fall migration. Migration data of 31,226 GPS
relocation points were collected from 50 migrating elk during the four years of study. Stopover
relocation points were 99% of the migration data.
Variable Selection
In chapter three I determined elk used stopovers during migration. A number of GIS data bases
were available to represent the availability of forage for ungulates during migration. To assess
characteristics of stopovers I identified 9 potential variables from the literature. They were
elevation, terrain ruggedness, canopy cover, aspect, open area, distance to roads, road density,
NDVI (forage quality) and predation habitat. A wolf resource selection function was available
for the area (Muhly et al. 20010) to represent wolf habitat. NDVI was not readily available to
represent forage quality which is expected to be important to elk migration in mountainous areas.
I used open meadows, canopy cover and elevation as alternatives to NDVI. Some of the best
areas of forge supply are found in open meadows. Open meadows and security cover such as
trees can be characterized by canopy measurements. Aspects comprised of southerly slopes will
green-up sooner in the spring and altitude will represent the elevation gradient. These are all
attributes of the process of vegetation green-up. Predation risk is an important consideration for
ungulates as they migrate (Pomeroy et al. 2006, Sawyer 2009). Reduced predation risk is
expected to be part of the benefits of migration, although the risk of predation may affect
stopover selection by animals (Pomeroy et al. 2006, Sawyer 2009). To reduce the risk of
predation ungulates will use habitats of rugged terrain, higher altitude, increased distance from
roads and areas of lower road densities. Elk distance from roads and road densities have been
used to represent human disturbance to elk (Rowland et al. 2000, Frair et al. 2008, Webb et al.
2011) and an RSF for wolves will represent a important predator for elk in the area (Muhly et al.
2010). I propose these metrics may be able to represent characteristics of elk stopovers. I created
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resource selection function (RSF) models for both seasonal migrations to evaluate habitat
selection variables for female elk during different spatial and temporal scales. I compared
characteristics of stopovers with random points found within the home range of the Castle-
Carbondale elk herd. RSFs were binomial models with dependent variable 0 (associated habitat
features of random points) or 1 (with associated habitat points used by elk). Random points were
selected from within the minimum convex polygon of the elk population home range. For all
analyses 2:1 ratio of random points were used for comparison to elk habitat points. I evaluated
habitat selection for only female elk using logistic selection functions (R Development Core
Team. 2009) to estimate resource selection functions (RSFs: Johnson et al. 2006, Manley et al.
2002). Used and random available locations were related to eight variables: wolf RSF (wolfrsf),
canopy cover (canopycover), south aspect represented as cosine aspect (cosaspect), log
transformed altitude (L.altitude), log transformed ruggedness (L.ruggedness), log transformed
density roads within three kilometers (L.densroad3k), log transformed distance to road
(L.distroad) and openarea. Correlation among variables was assessed using Pearson’s
Correlation (r > 0.7 was considered highly correlated) and any variable higher was removed
because of high correlation with other variables. The variable percent canopy and open area had
a high correlation with each other. I chose to use both variables but not in the same model. Nine
a priori models (Table 4-1) were considered for both spring and fall migration events and
Akaike’s Information Criteria (AIC) was used for model selection (Burnham and Anderson
2002).
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Table 4-1 Variables used in the spring and fall elk migration models with predicted effects of
variables
Description Data Source Data resolution
e
Predicted
effected
effect
wolfrsf Wolf resource
selection function
Muhly et al.
2010 Oikos 30 m -
canopycover % canopy cover SRD 30 m -
cosaspect Aspect SRD 30 m +
L.altitude Log transformed
altitude
GIS data SRD 30 m -
L.ruggedness Log transformed
terrain ruggedness
GIS derived
Riley et al. 1999 30 m -
L.densroad3k Log transformed road
density within 3km
(km
2 per km)
Road data
SRD
30 m +
L.distroad Log transformed
distance to nearest
road
Road data
SRD 30 m +
openarea Open areas SRD
Collinear with
Canopy cover –
used in different
models
30 m -
*Alberta Sustainable Resources and Development (SRD)
Display of the RSF models occurred in GIS using the following relationship:
RSF(x) = exp(β1x1 + β2x2 + … + βnxn)
Where (x) value of landscape variables, β is the selection coefficients of that variable (Manley et
al. 2002). Models were calculated in R statistical software package. AIC was used to confirm
the best model for both spring and fall migration.
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RESULTS
I collected data from 50 migrating elk comprised of 12 males and 38 females from 2007 to 2010.
Only the GPS data points collected during migration of the 38 female elk were used for stopover
characteristics analysis. The wide differences in Δ AICc and wi between the different models
confirm the strength of the best model (Table 4-2). AIC selected the same model as the most
parsimonious model for spring and fall migration (Table 4-2, 4-3).
The spring model consisted of the best model being rated much higher than the second model
based on the difference in the Δ AICc and wi values (Table 4-2). Fall migrations best model
contained the same variables as the spring with the difference between the best and second
model less distinct (Table 4-3). This suggests for both models the location points in stopovers
were significantly different from random points in the study area.
Table 4-2 Spring Migration AIC Candidate RSF Model Rankings
AIC Δ AICc wi
wolfrsf+ canopycover+cosaspect
+ L.altitude+L.ruggedness+
L.densroad3k +L.distroad
53978.82 0.0 1.0000
wolfrsf+ openarea+cosaspect
+L.altitude+ L.ruggedness+
L.distroad +L.densroad3k
54073.63 94.8 0
canopycover+cosaspect
+L.altitude+ L.ruggedness+
L.distroad+ L.densroad3k
54575.57 596.8 0
openarea+cosaspect +L.altitude+
L.ruggedness+ L.distroad+
L.densroad3k
54682.17 703.3 0
wolfrsf+ canopycover+cosaspect
+L.altitude+ L.ruggedness 54726.11 747.3 0
wolfrsf+ openarea+cosaspect
+L.altitude+ L.ruggedness 54819.45 840.6 0
canopycover+cosaspect
+L.altitude+ L.ruggedness 55298.5 1319.7 0
openarea+cosaspect +L.altitude+
L.ruggedness 55405.55 1426.7 0
Null model 61452.08 7473.3 0
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Table 4-3 Fall migration AIC candidate RSF model rankings
AIC Δ AICc wi
wolfrsf+ canopycover+cosaspect
+ L.altitude+L.ruggedness+
L.densroad3k +L.distroad
55764.73 0.0 0.9941
wolfrsf+ openarea+cosaspect
+L.altitude+ L.ruggedness+
L.distroad +L.densroad3k
55774.99 10.3 0.0059
canopycover+cosaspect
+L.altitude+ L.ruggedness+
L.distroad+ L.densroad3k
56155.12 390.4 0
openarea+cosaspect +L.altitude+
L.ruggedness+ L.distroad+
L.densroad3k
56167.32 402.6 0
wolfrsf+ canopycover+cosaspect
+L.altitude+ L.ruggedness 58685.44 2920.7 0
wolfrsf+ openarea+cosaspect
+L.altitude+ L.ruggedness 58693.35 2928.6 0
canopycover+cosaspect
+L.altitude+ L.ruggedness 59060.6 3295.9 0
openarea+cosaspect +L.altitude+
L.ruggedness 59073.37 3308.6 0
Null model 61368.69 5604.0 0
In both spring and fall models, stopover sites had the following attributes;
lower canopy cover,
southern facing slopes,
higher probability to encounter a wolf,
lower altitude,
high road density,
large distance from road.
Four variables found in both seasonal migration models had a positive effect on the model. The
variables were wolfrsf, ruggedness, density of roads within three kilometers and distance (Table
4-3, Table 4-4). These results suggest that elk selected areas where wolves could be present;
terrain is rugged, with road densities within three kilometers less than one kilometer per km2 and
distances from roads greater than 486m. For per cent canopy cover, aspect and elevation, there
was a negative relationship with elk stopovers (Table 4-3). My model suggests elk stopovers
were in areas of lower canopy cover, lower elevation, and more southerly aspects of the
landscape (Table 4-3).
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Table 4-3 Best Spring Female Elk Migration Model
Estimate Std. Error
+/-
(Intercept) 50.6300 0.9289
wolfrsf 0.0303 0.0012
canopycover -0.0077 0.0004
cosaspect -0.0964 0.0152
L.altitude -18.6800 0.2982
L.ruggedness 1.7760 0.0472
L.densroad3k 1.4260 0.1016
L.distroad 0.4859 0.0201
Table 4-4 Best Fall Female Elk Migration Model
Estimate Std. Error
+/-
(Intercept) 21.8600 0.8792
wolfrsf 0.0255 0.0013
canopycover -0.0025 0.0003
cosaspect -0.0750 0.0149
L.altitude -10.0900 0.2752
L.ruggedness 1.3400 0.0483
L.densroad3k 3.5830 0.1067
L.distroad 1.1290 0.0275
Migration metrics for elk stopovers were slightly different in spring compared to fall use (Tables
4-5, 4-6). Elk preferred lower elevations, lower canopy cover, southerly aspects, road densities
of 1km per km2, in rugged terrain and were found on average 525m from a road during spring
migration (Table 4-5). In the fall elk selected higher elevations for travel, a southeast aspect,
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areas of higher canopy cover, .98km per km2, and a mean distance of 678m from a road (Table
4-5).
Table 4-5. Spring stopovers characteristics of the Castle – Carbondale migratory elk, 2007 -
2010
Variable mean sd
+/- Range
Altitude (m) 1488.37 129.40 1198 - 2169
Aspect ( ° ) 162.57 80.86 -1 – 359.34
Canopycover (%) 27.94 30.80 0 - 83
densroad3k (km/km2) 1.00 0.47 0 – 2.68
Distroad (m) 525.87 407.07 0 - 3600
ruggedness 18.98 10.00 0 – 64.24
Table 4-6 Fall stopover characteristics of the Castle – Carbondale migratory elk, 2007 -2010
Variable mean sd
+/- Range
Altitude (m) 1547.04 142.24 1200 - 2192
Aspect ( ° ) 152.80 93.80 -1 – 359
Canopycover (%) 32.93 31.83 0 - 83
densroad3k (km/km2) 0.98 0.419 0- 2.7
Distroad (m) 677.57 447.90 0 - 3356
ruggedness 20.11 9.152 0 – 61.20
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DISCUSSION
Individual elk exhibited a variety of selection differences between the mean of their group for
each migration season (Table 4-5, Table 4-6). Fall migration primarily differed from spring
variables by an increase in distances to roads, canopy cover, terrain ruggedness and elevation.
Elk models in my analysis had positive coefficients for elevation, wolf RSF, road density and
distance form roads indicating a preference or tolerance for these variables during use of
stopovers. Elk used stopovers while avoiding human disturbance were apparent by the response
of elk willing to be at risk in wolf habitat rather than the negative effect of disturbance by
humans which are associated with roads, hunting activity and road densities (Table 4-5 and
Table 4-6). Predation effects from wolves were limited to the one wolf pack in the area during
the years of study so it may be perceived by elk the risk was low or infrequent. Coefficients from
the elk logistic regression in spring and fall indicated most elk selected for areas with low to mid
elevation, low per cent canopy cover, lower road densities and hundreds of meters away from
roads.
Elk in the Castle-Carbondale herd displayed increased mean values for elevation, per cent
canopy cover, terrain ruggedness and distance from roads in the fall compared to spring
migration. A number of effects increased during fall migration, possibly due to higher use of
roads by recreationalists and hunters (Proffitt et al. 2009, Webb et al. 2011), further suggesting
the variables were strong in detecting elk resource selection. Similar results have been noted in
other studies where human activities such as recreation, hunting, timber harvest, roads and oil
and gas development occurred (Frair 2005, Naylor et al. 2009, Proffitt et al. 210, Webb et al.
2011). Elk occupying landscapes with human disturbance are known to adjust their movement
strategies away from human disturbance sources such as roads, hunting, and recreational
activities (Naylor et al. 2009, Proffitt et al. 2010).
Roads
Areas with high road density may not have patches of forest cover large enough to provide
effective habitat for elk, particularly in hunted populations (Rowland et al. 2004). Extensive
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shifts in elk distribution away from roads are a widespread phenomenon, and, at a landscape
level, have the potential to affect elk carrying capacity and elk distribution away from high value
habitats near roads or human disturbance (Rost and Bailey 1979, Lyon 1983, Edge and Marcum
1991, Rowland et. al. 2000).
In the current study the mean distance elk avoid roads during the spring was 526m (SD +/-
407.07) and in the fall it was 677m (SD +/-.447.09). Based on the SD of avoidance of elk to
roads it appears a large degree of variability of individual elk occurs in response to roads with
distance from road values ranging from 0 m – 3600m.This suggests there is a wide range of
tolerance by individual elk for roads. This avoidance of roads is may be representative of the
wide range of responses depending on sex, age, or seasons (Vistnes et al. 2004). Females with
young are usually the most sensitive (Appollonio et al. 2005, Ciuti et al.2004). Road avoidance
may lead to an increase in ungulate density in areas away from potential disturbance sources,
resulting in increased competition or greater risk from predation (Gill and Sutherland 2000,
Vistnes and Nellemann 2007). For avoidance behaviour to occur there needs to be alternative
habitat available, although it may not be the same quality of habitat the animal was displaced
from. This will result in animals displaced to lower quality habitat (Gill et al. 2001).
In my study, stopover locations during both elk seasonal migrations exhibited selection for areas
of low road density (Table 4-4, 4-5). Their distribution indicates avoidance of areas less than
526 m from roads (mean distance) during spring migration and 668 m during fall migration.
Using an RSF model and GPS telemetry data from elk in West Central Alberta, researchers
(Frair et al. 2008) found the effects from roads saturated the landscape. There were no refuges
greater than one kilometre from a road when the road density is approximately 1.6 km km2. The
elk population in my study selected areas with road densities of approximately 1km per km2
within a distance of three kilometers from their relocation point.
Research has shown anthropogenic activities can create conditions that increase productivity of
forage resources for elk, such as some timber harvest methods, agriculture or prescribed burns
(Fraire et al. 2008, Rumble and Gamo 2011). Yet these same human influences can have a
negative impact on elk by reducing and degrading habitat through road development, reduction
of security cover, and increasing the subsequent vehicular traffic on roads (Friare et al. 2008,
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Rowland et al. 2000). Such changes influence elk behaviour and fitness by requiring increased
vigilance (Lung and Childress 2007), and elk avoidance of suitable habitats near major roads or
in areas of high road density (Boyce et al. 2010, Fraire et al. 2008). In turn, increasing road
networks provide humans easy access to elk habitat, which can lead to increased elk mortality
due to animal harvest or vehicle collision and a reduction in suitable habitat due to avoidance
from an expanding human disturbance footprint (Benitez-Lopez et al. 2010, Webb et al. 2011).
Castle-Carbondale elk are exposed to all these human created pressures to varying degrees on
both their seasonal ranges and migration corridors (Moorehouse 2010, Muhly 2010, Northrup
2010).
My study suggests elk responses to wolf predation risk (RSF model of SW Alberta wolves,
Muhly et al. 2011) are less than responses to human predation risk represented by roads and road
densities. Proffitt et al. (2009) indicated during their study where hunters occurred, elk responses
to wolves were less than responses to human predation risk.
Percent Cover of Canopy
Migrating female elk selected stopovers with low forest canopy cover (mean = 28% spring and
33% fall) when compared to random locations in their home range. Lower canopy cover is
typically related to greater forage availability in forests with a more open over-story. During
spring migration low canopy cover forests or meadows would green-up sooner as elk migrate to
higher elevation summer ranges (Hebblewhite et al. 2008).
Thirty-two percent of the elk migrated through the footprint of the 2003 Lost Creek fire where a
rich supply of forbs and grasses would be available in spring in an area of low canopy cover.
Research in Yellowstone National Park after the large fires of 1988 reported that grass biomass
increased quickly in a few years (Romme et al. 2011) and patterns of elk habitat use followed
forage recovery patterns. Elk used burned forests randomly during the first three years post fire
then selected burned forests 12-14 years post fire (Boyce et al. 2003, Mao et al. 2005) and are
predicted to see these positive effects for up to 30 years (Singer et al. 1989). Detailed elk
migration movements are not known before the Lost Creek fire occurred, but present use and
research suggests migrating elk are and will be able to utilize the post fire vegetation for many
years to come.
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Female elk selecting for lower canopy cover at stopovers may also be displaying this behaviour
in an attempt to find the balance between quality food sources and predation risk to balance food
and danger for both the female and her calf (Kotler eta al. 2004, Pomeroy et al. 2006). Lower
canopy cover would provide more light for plant growth of forbs and grasses as well as
providing greater visibility to detect predators such as wolves or humans (Laundre et al 2001).
Alternately, risk of predation by wolves may increase selection for forested habitats where
detection of prey by predators is lower (Creel et al. 2005). In SW Alberta elk responses to wolf
predation risk (RSF model of SW Alberta wolves) seem to be less than human predation risk
represented by roads and road densities. Proffitt et al. (2009) indicated in their study where
hunters occurred, elk responses to wolves were less than responses to human predation risk.
Terrain Ruggedness
Terrain affects the grazing and traveling behaviour of ungulate species such as elk (Anderson et
al. 2005, Forester et al. 2007). Elk react to wolf presence by increased use of steep slopes and
rugged terrain combined with increased pathway sinousity (Laporte et al. 2010). The use of
rugged terrain and steep slope by elk as refuge from predation has been documented in elk
studies (Frair et al. 2005). Such a response is common in ungulates and is an effective anti-
predator response (Bleich 1999, Hamel and Côté 2007). In a hunted elk population such as the
Castle-Carbondale herd, elk may respond to humans in similar ways as they do canine predation
risk (Proffitt et al. 2010). Therefore, the risk-disturbance hypothesis may also explain avoidance
by animals of nonlethal human activity, which suggest animals would display the same
behaviour used by prey when encountering human predators (Berger et al. 1993, Frid and Dill
2002). It is probable that the results of the logistic regression (elk selecting for rugged terrain) is
a response to both human disturbance represented by roads and the potential to encounter a wolf.
The disturbance is greater during the fall probably due to the influence of hunting activity
(Proffitt et al. 2010).
Using rugged terrain is an effective method to reduce predation risk by elk. Although my model
does not examine the interaction between these variables, the overall separate effects of roads of
wolves are less predation risk than roads.
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Aspect
Studies have noted elk prefer specific aspects depending on the season. Skovlin et al. (2002)
found elk in winter preferred upper south facing slopes because of wind and solar radiation
where slopes become bare of snow. Results from western Oregon (Moeller 2010, Witmer and
deCalesta 1985) found migratory elk spent a greater percentage of their time on southern aspects
during all four seasons of the year. During the four years of my study, the elk population
typically used stopovers with southern aspects of 153 and 163 degrees during spring and fall
migration. There were individuals that used northerly and northeast facing slopes but they were
not common. Particularly during the spring, south and southwest slopes would green up the
quickest providing nutrient rich forage for migrating elk to replenish their bodies after winter.
Wolf
My model suggests elk are willing to risk contact to potential wolf predation rather than risk
exposure to human activity associated with roads. This aversion to human activity which was
represented by roads and road densities increased in the fall during hunting season (677m versus
525m). Such a behavioural response may suggest that elk are able to discern temporal variation
in predation (Gude et al. 2006, Proffitt et al. 2010). In Yellowstone National Park, elk respond to
wolf predation risk by moving to another area within one or less days after exposure (Creel et al.
2005). Elk may also respond to wolf predation risk by choosing forested areas where risk of
detection by predators is lower (Creel et al. 2005) or at other times elk groups have selected
grassland flats for their ease of detecting wolves or movement and maneuverability for escape
(Proffitt et al 2010). When exposed to predation risk from humans the behavioural response was
greater than if the risk was from wolves (Proffitt et al. 2009). Elk respond to changes in
predation risk over time periods of a week or months but they did not respond during diurnal
time scales (Proffitt et al. 2010).
CONCLUSION
My analysis of the Castle-Carbondale elk herd use of stopovers during migration indicates
stopovers are preferentially selected based on eight of nine habitat metrics when compared to
random sites within the MCP home range of the elk population. Elk use the same stopovers
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during each season of migration denoting the areas importance for elk. A study of mule deer
(Sawyer and Kaufmann 2011) also identified annual use of stopovers and they found higher
forage quality was available at stopovers compared to movement corridors. Forage values in
stopovers also increased along the elevational gradient as distance from winter range increased
(Sawyer and Kaufmann 2011). My study found elk used stopovers repeatedly during spring
migrations but stopover use shifted away from spring sites during fall migration and hunting
season (Table 4-4, 4-5).
Conservation of stopover sites for migratory birds has become a worldwide initiative reflecting
the significance of the areas to avifauna (Hutto 1998a). Birds will stop at these sites year after
year during migration. In the case of ungulate use, stopovers are less known but this study
indicates elk have a preference for sites along the migration route where they stopover regularly.
Another study of migrating mule deer showed fidelity to stopovers during different seasons and
years, suggesting the sites may be important for conservation of migratory ungulates (Sawyer
and Kaufman 2011). They suggested, the importance of individual stopovers along the
migration route will be difficult to quantify (Sawyer and Kaufmann 2011). In the Castle –
Carbondale migration network there are stopovers which overlap with winter range and a
number are nodes or hubs of connection for multiple migration routes. While all stopovers may
have important forage resources, security features or combinations of both. Stopovers used
during multiple seasons time such as winter and spring migration or spring and fall migration
may require a higher priority of conservation. Additional study could develop models using
vegetation indices such as NDVI associated to each elk GPS point during migration. Allowing
for two way interactions in the model between the wolf RSF and roads could provide additional
insights to my current results.
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CHAPTER FIVE: CONNECTIVITY OF ELK MIGRATION PATHWAYS IN SW ALBERTA
ABSTRACT
Increased recreation activity, industrial development and predator populations have the potential
to influence ungulate movements such as seasonal migrations. Conservation efforts often focus
on the habitat, viability requirements and connectivity for umbrella or keystone species such as
elk. In this study I use two connectivity modeling methods designed to assess connectivity, least
cost path and circuit theory. I obtained an existing resource selection model (RSF) of elk use in
SW Alberta then used the inverse of these data to develop a cost surface for use in the model
(Connectivity Analyses Toolkit). Preliminary results suggest the model confers with expert
knowledge based on regional and local scale assessments. Further quantitative assessment is
required to fully validate the model using migration and dispersal data not used in the model
development.
INTRODUCTION
Loss of habitat and fragmentation are detrimental to biodiversity from global to local spatial
scales (Crooks and Sanjayan 2006, Noss and Daly 2006, Laita et al. 2011). Fragmentation has
always been part of the ecological variation of habitat and does not necessarily threaten many
species (Baggio et al. 2011). What is of concern is the accelerated nature of fragmentation due
to human population growth, infrastructure development and urban sprawl increasing the rate
and scale of fragmentation that threatens species persistence (Baggio et al. 2011). Habitat loss
from human sources reduces the total amount of habitat by breaking up core areas necessary for
many species (Kindlmann and Burel 2008). This creates habitat fragmentation which confounds
and increases the effect of direct habitat loss (Andren 1994). The ecological effects of both are
intertwined and may be understood or measured using the concept of connectivity (Gilbert-
Norton et al. 2010, Laita et al. 2011). The concept of connectivity refers to the connections
between species and the habitats they utilize (Schumaker 1996). A particular landscape will
provide different degrees of connectivity, depending on behaviour, habitat preferences and
dispersal abilities of a particular species (Calabrese and Fagan 2004). Although species vary a
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great deal in their response to fragmentation it is invariably detrimental to natural ecosystems
(Johnson et al. 2005, Johnson and Klemens 2005).
Landscape permeability, also known in landscape ecology as connectivity, assesses the degree to
which organisms are able to traverse a landscape (Taylor et al. 1993, Tischendorf and Fahrig
2000). Connectivity is comprised of both structural and functional connectivity, where structural
connectivity relates to linkage of habitat patches by their adjacency (Keitt et al. 1997).
Functional connectivity relates to linkage of habitat patches by processes that reflect dispersal
and movement behaviour of species (Brooks 2003, Goodwin and Fahrig 2002). The foundation
of the functional connectivity concept is that the connectivity experienced by an animal is based
on the behavioural responses of the animal to physical landscape structure (Kindlmann and Burel
2008).
A reduction or obstruction of animal movements can have significant consequences for
conservation of biodiversity (Taylor et al. 1993, Minor and Urban 2008). Maintaining habitats
for animal travel areas enables juvenile dispersal, recolonization of unused habitats, seasonal
migration and metapopulation dynamics (Gilpin and Soule 1986). With climate change added to
the list of habitat influences managers need to consider long term management strategies for
maintaining movements of animals. Animals will need suitable habitat for range shifts to
conserve movement opportunities and genetic diversity (Minor and Urban 2008, Schemske et al.
1994).
The loss of connectivity throughout landscapes worldwide has led researchers to investigate the
effects of habitat fragmentation and human disturbance to animal migrations (Berger et al. 2008,
Harris et al. 2009, Hebblewhite et al. 2008, Mysterud et al.2001, Sawyer et al. 2009, Voeten et
al. 2009). Completing these migration movements are believed to be essential to migratory elk
populations and meta-populations (Coulon et al. 2006, Schmiegelow 2007). Elk migration is an
adaptive behavioural strategy that evolved to avoid constraints on resource availability in
temperate regions (Cook et al. 2004, Hebblewhite 2008). Movement to seasonal mountain
ranges allows elk to access optimal patches of nutrient rich vegetation for an extended time
period, enhancing fitness and reproduction (Mysterud et al. 2001, Phillips and Alldredge 2000,
Smallidge et al. 2010). In turn, elk contribute to ecosystems function and biodiversity by their
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grazing pressure on plants and influence on soil dynamics (Frank and Goffman 1998, Kie and
Lehmkuhl 2001). Migrating elk are part of a functioning ecosystem and maintaining the
connectivity of their migration pathways to ensure the migration strategy is not discontinued is
valuable. Connectivity for ungulates is not only important to migration but to ungulate dispersal.
Fragmentation can affect ungulate meta-population dynamics such as gene flow between
subpopulations (Coulon et al. 2004), therefore conserving dispersal routes for ungulate is
essential.
My objective for this chapter is to complete a local and regional connectivity analysis for elk to
identify areas where conservation efforts could be implemented for elk migration and dispersal.
Such knowledge will add to the existing corridor research completed for carnivores (Apps 1997,
Kansas 2002, Chetkiewicz and Boyce 2009).
STUDY AREA
The Castle-Carbondale study area encompasses approximately 1004 km2 in southwest Alberta.
It represents a large component of an internationally recognized area known as the Castle Crown
of the Continent (Figure 5-1). Alberta Sustainable Resources administers 100% of the public
forest reserve. On the eastern boundary of the provincial forest reserve are private ranchlands
intermixed with cropland. The study area includes portions of two municipal districts (M.D.
Pincher Creek, Municipality of Crowsnest Pass). Livestock grazing occurs seasonally on public
land and year-round on private land. Industrial activities in the area include forestry and natural
gas extraction. Human activity on the landscape is widely distributed, comprised of random
camping, off-road vehicles, mountain biking, hiking, hunting, and fishing combined with winter
activities of snowmobiling and skiing.
Elevations range from 1250 to 2330 meters. The four kilometre wide strip of private land on the
eastern boundary represents a transition zone between grassland and montane, continuing
westward along montane foothills, which quickly rise to subalpine and alpine environments of
high elevation mountains along the Continental Divide between Alberta and British Columbia,
Canada. The area is composed of two natural regions and three natural subregions. The Rocky
Mountain natural region is comprised of the Montane and Subalpine subregions and the
Grassland natural region includes the Foothills Fescue subregion. Environmental characteristics
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of the Rocky Mountain natural region include cool summers (13.9 Celsius), short growing
season, high annual precipitation (798 mm) and the highest snow loads found in Alberta
(Downing and Pettapiece 2006). The landscape is shaped by the prevailing Chinook winds
which create snow-free southwest facing slopes exposing winter grass and shrub forage for
ungulates. Montane and Subalpine subregions consist of rugged terrain with elevations from
825m to 2,300m. Dominant vegetation is lodgepole pine (Pinus contorta) Douglas fir
(Pseudotsuga menziesii), aspen (Populus tremuloides), subalpine fir (Abies lasiocarpa)
interspersed with grassland slopes, meadows, wetland complexes (Downing and Pettapiece
2006) and clearcuts. The Foothills Fescue subregion typically is rolling hills (elevation 800 m to
1,525 m) dominated by mountain rough fescue (Festuca campestris), bluebunch fescue (Festuca
idahoensis) and Parry’s oatgrass (Danthonia parryi). Portions of the subregion in the eastern
portion of the study area have been converted to cropland or tame pasture grass species.
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Figure 5-1 Study area for Castle-Carbondale elk, 2007 – 2010 (location 694298 E 5483627 N)
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MATERIALS AND METHODS
Capture, Collaring, and Data Collection
A helicopter and net-gun were used to capture 38 female and 14 male migratory elk on the
winter ranges of southwestern Alberta from January to March during 2007-2010 (University of
Alberta [Edmonton, Alberta, Canada] Animal Care Protocol number 353112). Elk were
blindfolded and hobbled to allow collaring and sampling with low impact to the elk. Elk were
fitted with Lotek 4400M GPS, 4400 GPS/Argos collars (Lotek,Newmark Ontario, Canada) and
Telonics GPS (Telonics, Mesa Arizona) equipped with mortality sensors that increased pulse rate
if the collar remained motionless for >6 hours. GPS units were programmed to obtain location
fixes every two hours (i.e. 12 per day). I located radio-collared elk from access roads at least
once a month and some subpopulations such as the Castle-Carbondale every week to confirm
location and status of the elk. Collars from elk that died were refitted on new elk. The collars
were outfitted with a remote drop off device programmed to disengage after 104 weeks. When
the device failed elk were recaptured by the helicopter with net-gun method to retrieve the
collars.
Network Models
A network modeling framework is well suited to assess connectivity of landscape heterogeneity
(Brooks 2006, Carroll 2012, Fall et al. 2007, Urban and Keitt 2001, Urban et al. 2009). A
network is represented by a set of nodes that are connected by edges that connect pairs of nodes
(Brande and Fleischer 2005) (Figure 5-2). When planned for conservation purposes, nodes
represent habitat patches, core areas or reserves and edges reflect the possibility for dispersal
(Minor and Urban 2008). Weights are assigned to nodes and edges to provide information
regarding their degree of connectivity, based on the size of nodes or the distance of edges in a
landscape. Including the spatial properties of nodes and edges is common in landscape
applications. Nodes can be defined as two dimensional patches with fixed locations and edges
can be defined as geo-referenced links between nodes connecting core nodes moving along
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routes of shortest or best connectivity based on suitability of the intervening matrix determined
by least-cost routes or circuit theory (Figure 5-2) (Carroll et al. 2011, Fall et al. 2007).
I conducted a method of regional and local analysis using current theory and shortest path
analysis to assess landscape connectivity for migrating and dispersing elk. The source area for
the local analysis was elk winter range and the targets were a long and narrow a north-south
orientated summer range on the eastern aspect of the Rocky Mountains. The approximately
5000 km2 regional connectivity analysis included seven elk subpopulations located in SW
Alberta. The analyses predicted the best connected pathways for migration and dispersal of elk
subpopulations at two different scales.
Figure 5-2 Network Modeling Framework
Data Analysis
I used the software package Connectivity Analyses Toolkit (CAT) for analysis. For an elk habitat
file I used a previously developed resource selection function (RSF) representing all elk in the
regional study area (Muhly et al. 2008). I used the inverse of the elk all season regional RSF
model to generate a cost surface for shortest path analyses. An assumption was made that higher
RSF values represented lower costs to movement than low RSF values (Chetkiewicz and Boyce
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2009). I transformed the elk RSF created for the regional study area into an .ascii file necessary
for connectivity analysis. There are three procedures to prepare the data for analyses and
presentation. The first is creation of hexmaps, second a graph file, and third a connectivity
shapefile which can be displayed in ArcMap GIS. Three types of linkage mapping methods are
possible, the shortest (least-cost path), current flow and network flow (Carroll et al. 2011). The
three techniques consider first the single shortest path, second the probalistic flow of all possible
paths, and lastly the optimal flow which will evaluate all possible paths but not use them all. For
my investigations the least-cost and current flow centrality metrics were used to evaluate
connections between all pairs of nodes on a landscape, both have similarities, but are very
complimentary when used together. The third method, network flow, was not used in this study
because of computational challenges of computer memory requirements and analysis times of
numerous days (Carroll et al. 2011). Different methods allow for different assumptions about
animal movement. Shortest path identifies and ranks the one or several shortest paths that
connect each pair of nodes on a graph and totals the quantity of shortest paths the node is
included in (Borgatti and Everett 2006). A loss of the node that is found within a large number
of the shortest paths will disproportionately lengthen distance and time travelled between nodes
(Brandes 2001). An inherent characteristic of shortest path is the individual dispersing is
assumed to have a landscape perspective of the optimum pathways available to it (Freeman
1977). Results from the shortest path analysis illustrate the minimum number of linkages within
the region whose loss would greatly reduce regional connectivity.
Current flow determines the centrality or importance of a node by how often, summed over all
node pairs the node is traversed by a random walk between two other nodes (Newman 2005).
This basically tabulates all paths between nodes, not only the shortest (McRae et al. 2008).
Current flow compliments the shortest path method by detecting areas of redundancy within a
possible linkage which could provide alternatives to the shortest paths. Areas of redundancy
provides insights to the potential resilience of the linkage and how it may be able to shift to
redundant areas to allow for changing environmental and land use patterns (Carroll et al. 2011).
Areas of narrow high current flow may identify pinch points, places where connectivity values
may be constrained in narrow linkages. Such narrow linkages could be further evaluated using as
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shortest path subset, to investigate how the pinch point may be improved to increase or maintain
its connectivity.
I used shortest path and current flow metrics in the program CAT to assess connectivity for
seven Rocky Mountain elk subpopulations across a regional landscape in SW Alberta. The
Connectivity Analysis Toolkit for the regional assessment used a new connectivity analysis
method where source and target patches are not designated (Carroll et al. 2011). I compare my
regional results with efforts from a multispecies linkage assessment across Highway 3 and local
knowledge of elk movement corridors in the area. A second analysis (local scale) used the two
complimentary connectivity metrics but designated a source (winter range) and target (summer
range) to assess connectivity of elk migration pathways. The local scale analysis extent was the
Castle-Carbondale elk subpopulation home range. The results of the local analysis were
compared with BBMM migration map outputs from Chapter 3.
RESULTS
Results from the regional analysis provide an assessment of the best shortest paths across my
regional and local study areas. The process ranks the shortest paths throughout the study extent
(Figure 5-3). GPS relocation data from collard elk found very few animals migrated north and
south (n=1), whereas a larger number of elk were noted to move north and south while
undertaking dispersal (n = 4). East and west movements are representative of migration or
dispersal. The regional shortest path assessment of connectivity predicts the minimal number of
quality movement areas across the landscape for elk. The analysis suggests there are numerous
quality movement pathways in the region which are predicted to provide connectivity for elk to
move east to west and north to south. These movement pathways would represent potential
dispersal corridors for elk between the seven subpopulations of elk found in SW Alberta, British
Columbia and populations of the northern United States.
In addition to the significance of maintaining regional connectivity it is important to conserve
local scale connectivity necessary for migration of elk in SW Alberta. Local scale shortest path
connectivity modeling predicts two areas of higher quality connectivity pathways for Castle-
Carbondale elk migration from their eastern winter range to the mountainous summer range
found along the continental divide in Alberta and British Columbia (Figure 5-4). The two
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pathways of highest connectivity correspond with population migration UD’s using the BBMM
in Chapter Three. The BBMM represents the UD of elk migration GPS locations from 38 female
and 12 male elk. In addition to the two highest quality pathways the shortest path analysis
indicates there are a number of other connected pathways as possible alternatives for elk
migration.
I conducted a second connectivity analysis using circuit theory methods (Figure 5-5). The output
from this method indicates there is a pinch point or narrowing in connectivity of the potential
migration pathway (yellow area). Adjacent to the pinch point of high connectivity there are
additional well connected areas suggesting that adjacent areas may be suitable for elk to shift
their migration pathway (dark blue area). Shortest path and current theory methods of
connectivity analysis provide complementary perspectives (Carroll et al 2011). The shortest path
denotes the shortest quality path for movement while the current theory method considers all
possible paths. Overlaying the current flow path output with the shortest path map provides
additional information to understand possible options for elk migration, particularly in areas of
narrow connectivity (Carroll et al. 2011). When interpreting the current flow map (Figure 5-5),
wider linkages such as the yellow does not mean that more area is needed to conserve
connectivity, it just means there are numerous options for movement that have good connectivity
(McRae et al 2008 ). For both analyses I assume that preferred high-quality habitat makes a
better corridor than less-preferred habitat.
DISCUSSION
The graph-theoretic approach provides a measure of habitat connectivity similar to
metapopulation theory which states that the importance of each habitat patch in maintaining
overall connectivity of the graph can be attributed to its topographical position and patch
characteristics (Urban et al 2009). The CAT provides tools for linkage mapping which focuses
on the relative importance of sites for maintaining connectivity across a landscape (Caroll et al.
2011).
With natural habitats being lost or changed throughout the world, conservation efforts are being
implemented to conserve plant and animal species. In Alberta as in a few other areas along the
Continental Divide, researchers have investigated the ability of rarer animals such as carnivores
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to move north and south along a continental travel corridor (Apps 1997, Weaver 2001,
Chetkiewicz and Boyce 2002, Carroll et al. 2001). These areas have been promoted by
international groups such as the Wildlife Conservation Society and Yellowstone to Yukon
Conservation Initiative (Yellowstone 2 Yukon 2004) to conserve North American animal
populations using indicator or umbrella carnivore species such as the grizzly bear (Carroll et al.
2001, Ray et al. 2005). Additional projects with similar connectivity and biodiversity objectives
use multispecies assessments comprised of a suite of animal groups (amphibians, birds,
ungulates and carnivores) (Penrod et al. 2001, Southern Rockies Ecosystem Project 2005,
Washington Habitat Connectivity Work Group (WHCWG) 2010, Home et al. 2012).
Multispecies connectivity research includes ungulates and other species guilds as part of
assessment of the connectivity for continental animal movement. The outcomes provide a
rounded ecological assessment of landscape connectivity. The results of my connectivity
analysis could compliment the knowledge learned from carnivore connectivity assessments to
provide additional understanding of wildlife movement along the Continental Divide.
In this study, I investigated the importance and modeled the existing connectivity of a portion of
the continental movement route using the ungulate species, elk. I have implemented a graph
theory method represented by two types of analysis: 1) shortest path (least-cost) and 2) current
flow methods based on circuit theory, to assess and identify potential movement areas of elk in
SW Alberta. The regional area of analysis provides insights to possible dispersal, migration or
exploratory routes for elk to British Columbia and across the International Boundary into the
United States. The regional study area also provides insights of potential movement linkage
zones for elk across Highway 3 in Alberta and B.C. Studies have noted Highway 3 as a fracture
zone for the movement of wildlife north and south along the Continental Divide (Apps 1997,
Chetkiewicz 2001, Clevenger et al. 2010). The shortest path results for elk support a number of
the linkage zones determined by expert opinion to conserve for multispecies movement across
Highway 3 (Figure 5-3). The least-cost analysis using RSF data from my elk study predicted
highway crossing areas in the Crowsnest West Linkage Zone as well as in the Crowsnest East
Linkage Zone. The highest rated corridor using expert opinion methods was the Rock Creek
Linkage where conservation efforts are in progress (Clevenger et al. 2010). The Crowsnest West
Linkage Zone is located in the Municipality of the Crowsnest Pass where land use consists of
land conservation efforts by the Nature Conservancy of Canada and human development
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activities such as country residential acreages and industrial development. These activities in the
Crowsnest Pass areas are located within the core winter range of the Crowsnest Pass elk
subpopulation. Local knowledge and a program called Road Watch have documented elk
crossing Highway 3 which bisects the winter range (Lee et al. 2006).
The least-cost analysis modeled multiple possible routes within the regional study area
suggesting habitat connectivity for elk is likely still reasonable. This is not a surprise since elk
are considered adaptable, habitat generalist species frequently occupying ecotones (Geist 2002).
Although research in the U.S. over the last few decades suggests increasing displacement of elk
from traditional and in some cases high quality habitats due to human activities (Rowland et al.
2005). High traffic volume roads such as Highway 3 represent a threat to connectivity for
wildlife movement north or south. As traffic volumes increase in the near term and if in the long
term Highway 3 is twinned the permeability of these movement areas will be reduced (Clevenger
et al. 2010). Elk movement across secondary Highway 507 is frequent as elk cross between
Lundbreck Hills and Byron Mountain. Two additional secondary crossings occur on Highway
507. The first is by the Castle River Bridge and the second is near the Screwdriver Creek
highway crossing.
The Livingstone Range and a majority of the Lundbreck Hills are comprised of controlled human
access to private land, low traffic volume roads, interspersed with small parcels of public lands.
Based on my analysis these areas appear to represent areas of higher quality connectivity for elk
than areas found in eastern sections of public land along the Continental Divide. Possibly this is
due to higher road density, traffic volumes or higher human activity on public lands which can
be significant human disturbance sources (Webb et al. 2011).
Castle-Carbondale Elk Migration Pathway Connectivity
A local scale analysis of the Carbondale elk subpopulation was conducted using a source habitat
patch defined by the eastern extent of the winter range with a target patched defined by the
westward edge of the elk subpopulations summer range. I used the least-cost path analysis and
circuit theory methods to determine the areas of least resistance for migration of elk and possible
pinch points. Based on a visual assessment of overlaying the least-cost path and circuit
migration pathways, I was able to identify potential areas on the migration pathway where
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connectivity has been reduced (Figure 5-6). The most connected pathways are depicted in red
with alternate routes shown in orange and pink. The best modeled routes for connectivity closely
mirror two of the migration routes from the BBMM analysis of the Castle-Carbondale population
(Chapter Three). Based on results of this model the current migration pathways have segments
that are well connected. The shortest path route also identified the mountain passes crossing the
Continental Divide from Alberta to BC as quality routes for elk to use. In fact they are the only
routes available to elk to move across the Continental Divide and are used by migrating elk.
During my study, two dispersing elk traveled through mountain passes to a new winter range in
British Columbia and Montana.
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Figure 5-3. Graph analysis of habitat connectivity for an elk population of SW Alberta using
two linkage mapping methods based on shortest path
Red is the best path, followed by yellow and then pink. The local area analysis boundaries are
represented by the rectangle outline.
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Figure 5-4 A local scale graph analysis of habitat connectivity for the Castle-Carbondale herd
from the Alberta population of elk using the shortest path technique.
Red is the best path, followed by yellow and then pink. Gas well sites are named WAT-#.
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Figure 5-5 A local scale graph analysis of habitat connectivity for the Castle-Carbondale herd
from the Alberta population of elk using the current flow technique.
Green areas are winter and summer ranges, yellow represents the best connected areas, next dark
blue fading to lighter blue representing lower connectivity. Gas well sites are named WAT-#.
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Figure 5-6 A local scale graph analysis of habitat connectivity for the Castle-Carbondale herd
from the Alberta population of elk using the shortest path and current flow techniques
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CONCLUSION
Using the shortest path and current flow methods the model predicted segments of known
migration routes for elk in a local analysis of the Castle-Carbondale study area. At a regional
scale the modeling results closely coincided with Highway 3 wildlife crossing areas determined
by expert opinion (Clevenger et al. 2010). One of the possible reasons for our positive results
was the availability of a fine scale RSF model built from recent elk GPS telemetry data in the
same study area. Although beyond the scope of this project, my connectivity analysis needs to
be validated to assess the models ability to predict known GPS dispersal routes for individual
animals (Sawyer et al. 2011). Results from my project indicate the ability of the CAT to model
potential movement zones appears to be effective. Further quantitative assessment is required to
validate the model’s ability to predict elk migration and dispersal corridors.
My study demonstrates the potential for the applied value of graph-based analysis to estimate
connectivity which may compliment other ecological data for landscape connectivity. One of the
challenges of modeling is to interpret model outputs appropriately given their limitations and
assumptions (Nichols 2001, Sawyer et al. 2011), realizing the best model predictions are
imperfect representations of the real world (Conroy 1993). My intent for the connectivity
modeling had two purposes. One was to provide additional information for managers to consider
in the balance of wildlife conservation and resource development and secondly to increase
awareness of wildlife connectivity requirements in SW Alberta.
.
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CHAPTER SIX: KEY RESULTS, MANAGEMENT RECOMMENDATIONS, AND FUTURE
RESEARCH
INTRODUCTION
Maintaining migrating elk populations in SW Alberta will require specific efforts to retain
critical habitats and landscape characteristics required by elk to continue their seasonal
movements from winter to high elevation summer ranges. These efforts will benefit elk and will
also help humans to utilize the same landscape and reduce detrimental effects. If elk were to
stop migrating, their contribution to the ecosystem would be lost due to reduced grazing on
summer and transitional ranges. Large keystone mammal species such as elk have been shown to
affect ecosystem processes such as nutrient flows, nutrient cycling and successional trajectories
of plant communities (Kie et al. 2003). A reduction in the area of elk distribution and subsequent
population size would be a loss of biomass for predators from winter and spring mortalities, and
direct predation of calves and adult elk through the seasons. The change in elk distribution
would impact vegetation dynamics by overgrazing on the winter range and undergrazing on
other ranges, resulting in a negative impact on plant productivity and biodiversity. Predator
species using elk biomass as a source of food may in turn change their distribution to overlap
with the changed elk distribution (Nelson et al. 2012). Finally, a permanent shift of elk and
predators to elk winter range would likely result in increased negative human / wildlife
interactions.
In Chapter Three, I documented the migration pathways of the Castle-Carbondale elk
subpopulation using the BBMM. Individual and population pathways were modeled using elk
GPS relocation points collected during migration. The Brownian bridge model framework was
used to prioritize the areas of most importance to the Castle-Carbondale elk subpopulation.
Chapter Four defined the characteristics of elk migration stopover sites as areas with rugged
terrain, low canopy cover, at mid elevations located greater than .5km from roads. For Chapter
Five, I used a resource selection function model of elk habitat use constructed from data in the
study are to assess connectivity of the migration routes and potential dispersal paths using
shortest path and circuit theory at both local and regional scales.
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RESEARCH FINDINGS
Migration Pathways
With greater than 90% of elk from the Castle-Carbondale subpopulation migrating, this research
will be very applicable to managing the elk herd. Knowing migration corridors and important
stopover areas will enhance wildlife managers’ ability to maintain migration movements of
migratory elk and to manage the impacts of human activities. GPS technology has improved,
enhancing my ability to study ungulates by providing increased frequency and accuracy of
relocation points, but the methods to analyze movement data are limited. It is limited by the
abilities of modeling to account for uncertainty in animal movements between known locations
(Horne et al. 2007, Sawyer et al. 2009) and by the difficulty to scale individual migration data to
population level routes. Until recently, migration was investigated by connecting successive
GPS location points of collared animals (Berger et al. 2006) which provided metrics such as
timing, distances traveled and movement rates of migration. The draw back from such methods
are that there is no defined area of route utilization based on error, thus we would not know if the
route is 10m or 1km wide (Sawyer 2010).
The quantitative framework I used, modeled migration routes for both individual and population
levels. I also calculated the Brownian bridge variance which is used to depict a migration route
with a variance estimate of relative use along the migration route. It provided an estimate of
probability of a elk migration UD that can be used to assess development options be it roads or
well sites away from the core areas of migration. My results also support results from other
studies (Sawyer 2010) where movement and stopover areas may be distinguished based on
different behavioural states. This is also consistent with other research that used non-linear
curve fitting (Johnson et al. 2002), state-space models (Forester et al. 2007), Markov models
(Franke et al. 2004), random walks (Morales et al. 2004) and first passage methods (Bailey and
Thompson 2006). Elk use of stopovers was followed by quick movements through travel routes
to a new stopover. This differentiation between movements may be a useful management
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opportunity, for my modeling found the elk population favoured some areas over others. These
areas could be targeted for conservation as well as habitat enhancement opportunities.
The BBMM analyses highlighted an important stopover at the junction of Castle and Carbondale
Rivers, located near the western boundaries of elk winter range. Elk are regularly observed here
in the spring, feeding in the large meadows surrounded by aspen where some of the first grass
green-up frequently occurs (Paton 2005). From this topographic hub, the elk select one of three
routes traveling westward along three drainages to different summer ranges. This stopover
within the winter range appears to be an important one for it is an area providing new spring
forage as elk migrate through the winter range. The combination of winter range and a migration
corridor/stopover in one area suggests it is very important for spring movement of elk to the
summer ranges and should be considered critical migratory habitat. The site is also located
within 1.5km of a well site and crosses a gated access road used by gas field workers. This
example illustrates how elk and human activity can be compatible within limits using appropriate
mitigation strategies.
Stopover Ecology
In Chapter Four, I develop a spring and fall resource selection function (RSF) for female elk
migration to understand their patterns of selection for stopovers and possible differences between
seasons. There were differences in use between stopovers by female elk during spring and fall
migrations. A comparison of habitat characteristics of stopover sites with random locations
within the Castle-Carbondale elk home range found stopover sites were in areas of rugged
terrain, with low canopy cover, mid elevations, and at least 500m away from roads.
Stopovers in the Sawyer study (2010) had higher forage quality compared to movement corridors
connected to them, forage quality improved as elevation and distance from winter range
increased. This would fit the strategy of migratory ungulates to follow the green-up of the most
nutritious vegetation to maximize energy intake during the growing season (Albon and Langvatn
1992, Fryzell et al. 2004, Holdo et al. 2009). In my study the largest concentration of stopover
areas were located in a 2003 Lost Creek fire footprint where forbs and grasses would green-up
quickly, providing rich forage for elk. Two other migration routes not passing through the burn
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had fewer stopover sites of a smaller area than the Lost Creek fire, possibly because elk using the
burn were inclined to stay in areas of very rich nutritional forage for extended time periods.
There appears to be differences in use between stopovers by female elk during spring and fall
migrations. A comparison of habitat characteristics of stopover sites with random locations
within the Castle-Carbondale elk home range found stopover sites were in areas of rugged
terrain, with low canopy cover, mid elevations, and at least 500m away from roads.
LANDSCAPE CONNECTIVITY FOR SW ALBERTA ELK
Landscape Connectivity for the Castle-Carbondale Elk Subpopulation
My study provides additional data regarding the effects of environmental and anthropogenic
effects on elk movement ecology. I delineate the migration pathways for elk for the Castle-
Carbondale subpopulation and assess connectivity of the landscape for elk movement at a
regional and local scale. My results will provide insights to help manage and possibly mitigate
for human influence on elk movement patterns, providing information to develop a strategy for
conservation and management. Here I summarize possible management opportunities based on
my study results.
MANAGEMENT RECOMMENDATIONS
1. Conserve stopover sites; particularly those that may be also used for calving, wintering
areas or by multiple migration routes. Stopovers are important areas for animals to rest,
forage and build-up body reserves critical for nursing and winter survival. This may
influence productivity. A long term reduction of female elk productivity will affect
population size.
2. When possible, plan new development outside of migration route core areas. A loss of
migration habitat could lead to eventual loss or reduction of migratory behaviour in elk.
Such a loss has the potential to increase human-elk land use issues. There may be a
reduction in ecological processes due to elk grazing and a possible change in distribution
of carnivores that utilize ungulates as food. The distribution change could be a shift in
wildlife from seasonal use of summer ranges in the mountain regions to wintering areas.
Increased wildlife use in areas of human settlement creates the likelihood of increased
wildlife management issues.
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3. Implement land management plans to conserve areas of winter range and migration
routes by putting private land into conservation easements or to have critical habitat
status on public land would be beneficial to elk and other species using the area.
4. Game management plans for elk should consider the impacts of harvesting males that
migrate through two wildlife management units during the rutting season and on to the
winter range.
5. Reduce and control human activity on roads within migration routes particularly new
road developments using a 300 - 1000m buffer from the migration route. The buffer size
will depend upon site conditions such as topography and forest cover. In dense forest a
300m buffer is adequate, but in open meadows or clearcuts elk can be disturbed by
certain types of disturbance 1 km away. Likewise terrain, measured by viewscapes could
have large effects. Since the intensity of road use is typically more critical than road
densities, in most cases the use of a gated road could be acceptable. New roads closer
than 500m from stopover sites may be acceptable if access within appropriate distance
(point 5) is controlled using gates and the roads are decommissioned after they are no
longer being used by industry.
6. Continuing to remove roads by gating or re-sloping road bed to reduce traffic volumes in
wildlife movement corridors would be another positive step to maintaining and
increasing connectivity for animals.
7. Conserve migrating elk highway crossing areas by building structures for them to move
under the highway or reduce speeds limits with signage on low traffic volume paved
roads.
F
UTURE RESEARCH
Recommendation: Develop studies to understand the link between elk productivity parameters
and level of disturbance which are important to understanding the costs of human development
in elk habitat.
Recommendation: Additional work is required on identifying development thresholds (e.g.
traffic volumes) at which elk use of migration pathways could be significantly reduced.
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Recommendation: Incorporating variables such as NDVI and volumes of road traffic into the
stopover model would enhance the existing model.
Recommendation: An important concept of maintaining linkage zones is to provide movement
corridors for multiple species. Future work could expand upon the elk connectivity map
products with additional species to build upon the expert based predictions currently available
for Highway 3 crossing areas and future road improvement projects which may occur on
Highways 22, and 507.
Recommendation: Compare predictions of least-cost and current flow models with empirical
data on dispersal.
Recommendation: Further analysis is required to understand the important role of dispersal in
SW Alberta elk populations.
My study may be the first verified account of dispersal and migration movements of young bull
elk to subpopulations of elk in Alberta, British Columbia and Montana. The sample size for
these movements was not large enough to allow for comprehensive analysis of why these
movements occurred or preferences of habitat during dispersal. Future examination of existing
data sets or additional field sampling of 2.5 year old bulls would help to understand the
movement of these individuals, which are important for the metapopulation dynamics of a
population.
Recommendation: Elk migration routes represent functioning corridors for movement between
seasonal ranges. During this study dispersing elk also used portions of the migration route to
disperse to other metapopulations. Further investigating the qualities and characteristics of a
migration route may provide insights into corridor conservation strategies and understanding.
Recommendation: Future connectivity analysis for elk would benefit from the use of a RSF built
with location points representing only migration time periods. This may best represent the spatial
and temporal movement periods of migrating and dispersing elk.
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Recommendation: Fine scaled analysis of stopovers sites regarding habitat features such as
vegetation association are important in public lands used as rangeland for cattle.
Recommendation: Repeating the delineati on of migration routes using BBMM for additional
migratory herds such as Crowsnest, Oldman and Livingstone.
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