The role of spatiotemporal variation in resources in the diverse movement strategies of temperate ungulates

The current framework for understanding large-scale animal movement strategies (i.e., migration, nomadism, or residency) suggests that each strategy is associated with specific combinations of resource spatial heterogeneity and temporal predictability. While there is support for this framework across ecosystems, modern tracking data has revealed that all three strategies can occur in a single population. Using 21 years of GPS data from seven populations (n = 239) of pronghorn (Antilocapra americana) and twelve populations (n = 283) of elk (Cervus canadensis) across Wyoming, USA, we examined the support for resource-based hypotheses in predicting the occurrence of migrants, nomads, and residents. Using model selection, we found support for the hypothesis that greater spatial homogeneity and less temporal predictability are associated with residency, and vice versa for migration or nomadism. However, spatiotemporal heterogeneity did not explain the differentiation between nomadic and migratory individuals. We found that climate and anthropogenic features influenced individual movements: elk were more likely residents if they experienced more mild winters, and pronghorn were more likely residents if they resided closer to roads. Our findings demonstrate that ungulate movement strategies are consistently linked to spatiotemporal resource variation across scales and identify additional mechanisms for localized behavioral differences.