Evaluating the Influence of Development on Mule Deer Migrations

Migratory ungulates are often exposed to anthropogenic disturbance along their migrations. Understanding the influence of development on migratory behavior and phenology tracking is critical to successful planning and conservation. It is well understood that impermeable barriers to migration have detrimental effects on migratory ungulate populations, but the influence of semi-permeable barriers, where connectivity between seasonal ranges is maintained, remains unclear. We used GPS collar data to evaluate the influence of development on behavior and phenology tracking of mule deer (Odocoileus hemionus) in western Wyoming, USA. We found that deer increased movement rate under intense development conditions, shifted stopover areas, but largely maintained fidelity to individual routes. Phenology tracking---the ability of deer to access the highest quality forage patches in spring---declined over time in areas with rapidly expanding energy development. These results indicate that development in migration routes will alter the behavior of deer and diminish the foraging benefit of migration, with potential to cause long-term decline of migratory populations.