The seasonal migrations of ungulates are increasingly threatened by various forms of anthropogenic disturbance, including roads, fences, and other infrastructure. Although roadway impacts (e.g., wildlife-vehicle collisions and landscape permeability) to species such as mule deer (Odocoileus hemionus) can largely be mitigated with underpasses and continuous fencing, similar mitigation may not be effective for pronghorn (Antilocapra americana) or other ungulate species that are reluctant to move through confined areas. The Wyoming Department of Transportation recently installed 6 underpasses and 2 overpasses along 20 km of U.S. Highway 191 in western Wyoming, USA, where we evaluated species-specific preferences by documenting the number of migratory mule deer and pronghorn that used adjacent overpasses and underpasses for 3 years (autumn 2012 to spring 2015) following construction. We also measured the amount of back-and-forth movement across the highway for each species through time. We documented 40,251 crossings of the highway by mule deer and 19,290 crossings by pronghorn. Of those highway crossings, 79% of mule deer moved under, whereas 93% of pronghorn moved over the highway. These strong species-specific differences were evident at both sites and support the notion that overpasses are more amenable to pronghorn than underpasses. Concurrently, we documented a 64-306% increase in the amount of back-and-forth movement of mule deer and pronghorn across the highway during migration periods. Such movement flexibility is presumed to improve their ability to respond to changing environmental conditions by easily accessing habitats on either side of the highway. Our results highlight that species-specific preferences are an important consideration when mitigating roadway impacts with wildlife crossing structures. Ó 2016 The Wildlife Society.

Animal populations face increased threats to mobility and access to critical habitat from a variety of human disturbances including roads, residential development, agriculture, and energy development. Disturbance from human hunting is known to alter habitat use in ungulates, but recent work suggests that hunting may also trigger the onset of migration. Whether this holds true across ungulate species and hunting systems warrants further empirical testing. We used global positioning system location data from mule deer (Odocoileus hemionus) in south‐central Wyoming, USA, to evaluate the sex‐specific effects of hunting on habitat selection and migratory behavior from 2016 to 2018. We modeled habitat selection before and during hunting season using a step selection function, and we used time‐to‐event models to evaluate if hunting triggered migration. We found habitat selection and migration timing to be sex specific. Males responded to hunting season by selecting security habitat away from motorized routes, whereas females used habitat through hunting season that retained higher forage quality. Weather, as indexed by temperature and precipitation (i.e., snowfall), influenced migration timing for males and females. Migration timing in males was influenced by migration distance, where individuals traveling >50 km tended to migrate earlier than individuals moving <50 km. For deer that survived to rifle season, hunting was less influential on migration timing than environmental factors. Rifle season increased the likelihood of migration by 2% in females and <0.01% in males compared to outside rifle season. Our findings suggest that roadless areas on mule deer summer ranges and within migration corridors reduce the effects of hunting disturbance. Consequently, managers may consider limiting the use of motorized vehicles as a method for reducing effects on migration from hunting disturbance. © 2020 The Wildlife Society.

Sexual segregation has been intensely studied across diverse ecosystems and taxa, but studies are often limited to periods when animals occupy distinct seasonal ranges. Some avian and marine studies have revealed that habitat segregation, when sexes differ spatially or temporally in use of the physical landscape, is common during the migratory period and characterized by sex-specific differences in migratory behaviors. Recent research highlights the importance of understanding movement patterns in the context of the full annual life cycle and highlights the need to extend relevant theories of sexual segregation to the migratory period. We tested predictions from two leading hypotheses of sexual segregation, the forage-selection hypothesis (FSH) and the reproductive strategy hypothesis (RSH) as applied to the migratory period. We collected global positioning system (GPS) location data for male and female mule deer (Odocoileus hemionus) in south-central Wyoming and northwest Colorado and tested the main predictions of the FSH and RSH. Both sexes showed high fidelity to their migratory routes, but route fidelity was more variable in males. Males also started spring migrations earlier, ended spring and autumn migrations later, and spent 22% more time on stopover sites during spring migrations. Consequently, males took twice as long in spring and 44% longer in autumn to complete migration. Our results revealed clear sex-specific migratory behaviors and supported predictions of the RSH that male foraging behaviors optimize body condition for the autumn rut, and females prioritize foraging while balancing reproductive constraints. Specifically, males timed their movements with spring green-up as optimally as females, and the timing of male migrations and use of stopovers suggested that males prioritized time in areas of high-quality forage. This refutes predictions of the FSH during the migratory period that males should consistently choose habitats with abundant, low-quality forage. Our findings provide an important contribution to sexual segregation theory by extending relevant theories to understand male and female movements during the migratory period.