Habitat use and migration ecology of mule deer in developing gas fields of western Wyoming

Increased levels of energy development across the Intermountain West have created a variety of wildlife and habitat management concerns. Because many of the energy resources in the region occur in shrub-dominated basins (e.g., Powder River, Piceance, Great Divide, and Green River basins), management concerns have focused on native shrub communities and associated species, including mule deer (Odocoileus hemionus). 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, I 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. My 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, I 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 reasonable 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 was relevant to mule deer, I again 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 1.9 and 1.5 stopovers for every 10 km increase in migration distance during spring and fall migrations, respectively. 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. My results suggest stopovers were a critical component in the altitudinal migrations of mule deer and that conservation of stopover sites may improve efforts aimed at sustaining migratory mule deer populations.