Evaluating the influence of energy and residential development on the migratory behavior of mule deer

Migratory ungulates are often exposed to anthropogenic infrastructure along their migration routes. Understanding the influence of such development on migratory behavior is critical to successful planning and conservation. Impermeable barriers have obvious and detrimental effects to migratory ungulate populations, but the influence of semi-permeable barriers, where the connectivity of migration habitat is maintained but the migration routes are compromised by anthropogenic development, remains unclear. We evaluated the influence of development on the migratory behavior of individual mule deer (Odocoileus hemionus) in western Wyoming, USA. We used fine-scale movement data to evaluate the influence of anthropogenic infrastructure on deer movement rates, stopover use, and fidelity to migration routes for individual animals across multiple seasons and years. Deer avoided human infrastructure when selecting stopover sites. Fidelity to migration routes and stopover areas, as measured by the degree of spatial overlap between years, was not influenced by development, except in one heavily developed area. Our results suggested that deer increased rate of movement, reduced time in stopovers, and shifted stopovers in areas of intense development. In most cases, deer maintained fidelity to migration routes, regardless of development, suggesting that deer mediated exposure to development by altering movement-rates and timing-rather than the routes they traversed. This work adds to a growing number of studies indicating that development can disrupt migratory behavior. Understanding how different types and intensities of development influence migration can help inform land-use planning and conservation of migratory ungulates.