Mule Deer Migration Project

Project Description 

Increased levels of energy development across the Intermountain West have created a variety of wildlife management and conservation concerns. Because many of the energy resources in the region occur in shrub-dominated basins, management concerns have focused on native shrub communities and associated species, including mule deer. Two of the more pressing concerns are how mule deer respond when critical habitats (e.g., winter range) are impacted by development and how their migration routes can be identified and prioritized for conservation.

To address the first, we examined how three types of natural gas well pads with varying levels of vehicle traffic influenced the winter habitat selection patterns of mule deer in western Wyoming. Our results showed that mule deer avoided all types of well pads and selected areas further from well pads that received high levels of traffic. Accordingly, impacts to mule deer could likely be reduced through technology and planning that minimizes the number of well pads and amount of human activity associated with them. To address the migration concerns, we developed a quantitative framework that uses global positioning system (GPS) data and the Brownian bridge movement model (BBMM) to: 1) provide a probabilistic estimate of the migration routes of a sampled population, 2) distinguish between route segments that function as stopover sites versus those used primarily as movement corridors, and 3) prioritize routes for conservation based upon the proportion of the sampled population that uses them. Mule deer migration routes were characterized by a series of stopover sites where deer spent most of their time, connected by movement corridors through which deer moved quickly. These findings suggest management strategies that differentiate between stopover sites and movement corridors may be warranted. Because some migration routes were used by more mule deer than others, proportional level of use may provide a metric by which routes can be prioritized for conservation. 

Although stopovers appeared to be a prominent feature of mule deer migration routes, the explicit study of stopovers (i.e., stopover ecology) has been limited to avian species. To assess whether stopover ecology has relevance to ungulates, we used fine-scale GPS data and BBMMs to quantify a suite of stopover characteristics and examine the ecological role of stopovers in the seasonal migrations of mule deer. Mule deer utilized a series of stopover sites in both spring and fall migrations, across a range of migration distances (18-144 km). Overall, mule deer used one stopover for every 5.3 to 6.7 km increase in migration distance during spring and fall migrations, respectively, and used the same stopovers year after year. Stopovers had higher quality forage compared to movement corridors, and forage quality increased with elevation, presumably because of delayed phenology along the altitudinal migration route. Stopovers likely play a key role in the migration strategy of mule deer by allowing them to migrate in concert with vegetative phenology and optimize their foraging during migration.

Project Publications 

Sawyer, H.S.M.J. Kauffman. 2011. Stopover ecology of a migratory ungulate. Journal of Animal Ecology 80:1078-1087.

Sawyer, H., M. J. Kauffman, R. M. Nielson, and J. S. Horne. 2009. Identifying and prioritizing ungulate migration routes for landscape-level conservation. Ecological Applications 19:2016-2025.pdf.jpg

Sawyer, H., M. J. Kauffman, and R. M. Nielson. 2009. Influence of well pad activity on the winter habitat selection patterns of mule deer. Journal of Wildlife Management 73:1052-1061.pdf.jpg

Project Reports

Sawyer and Kauffman. 2009. Identifying mule deer migration routes to and from the Pinedale Anticline Project Area pdf.jpg

Sawyer and Kauffman. 2008. Identifying mule deer migration routes in the Atlantic Rim Project Area pdf.jpg

Sawyer and Kauffman. 2008. Identifying mule deer migration routes along the Pinedale Frontpdf.jpg

Project News

Contact information

Hall Sawyer, Ph.D.
Western Ecosystems Technology (WEST), Inc.
200 South 2nd Street, Suite B
Laramie, WY 82070


 Hall Sawyer


SawyerMug.pngHall is a research biologist and project manager with Western Ecosystems Technology, Inc. (WEST). Hall earned a B.S. degree in wildlife biology from Colorado State University and M.S. and Ph.D. degrees in Zoology from the University of Wyoming. Hall worked with the Wyoming Cooperative Fish and Wildlife Research Unit as a research scientist from 1997-2001, coordinating research projects that focused on elk, mule deer, white-tailed deer, pronghorn, and bighorn sheep. Hall joined the WEST team in 2002 and his specialty areas include migration ecology, resource selection, animal capture, GPS-telemetry, and impact assessment of ungulates. He currently leads several long-term studies that evaluate the migration ecology and potential impacts of energy development on mule deer, elk, and pronghorn. Hall lives in Laramie, Wyoming and enjoys backpacking, skiing, rock climbing, and hunting.

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Project Funders

Wyoming Wildlife & Natural Resource Trust  ·  University of Wyoming, School of Energy Resources  ·  Bureau of Land Management  ·  Wyoming Conservation Landscape Initiative  ·  Wyoming Game & Fish Department  ·  Wildlife Heritage Foundation of Wyoming

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