Book Description

Seasonal migrations along elevational and latitudinal gradients allow a diversity of wildlife species to persist in the face of dramatic seasonal shifts in habitat quality. Recent work to better understand ungulate migration has produced a suite of analytical tools for identifying the mechanisms behind migration and quantifying associated behaviors. While environmental variables like weather and plant phenology are thought to be the main drivers of migration, emergent evidence suggests that anthropogenic disturbances, such as hunting, as well as intrinsic factors like age and sex can also influence migratory patterns. However, critical gaps in understanding of the influence of both the intrinsic and extrinsic factors that influence migratory behaviors remain common. We used three years (2016–2018) of GPS-collar data for a herd of migratory mule deer (Odocoileus hemionus) in south-central Wyoming to compare key migratory behaviors between sexes, identify factors that influence the timing of migration, and evaluate habitat selection in and around the autumn hunting season. Overall, migratory behaviors were sex specific. Both sexes showed high-fidelity to their migratory routes, but route fidelity was more variable in males. Males also migrated 30% farther on average, spent 14% more time on stopover sites, and took twice as long in spring and 44% longer in autumn to complete migration. Additionally, we found that weather, mainly precipitation events (i.e., snowfall), not hunting disturbance, was the main driver of autumn migration, increasing the likelihood of migration in both males and females by 14%. Our findings suggest that response to disturbance from hunting season is sex-specific. The hunted sex (males) more intensively sought refugia, whereas the less-hunted sex continued to use areas with good forage. Overall, our findings contribute to a broader understanding of migration ecology and the factors that influence migration and habitat selection of wild ungulates in western landscapes.