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

Abstract

Animal movement strategies are thought to be determined by the spatiotemporal variation of resources in an environment. Observations of various species indicate that the occurrence of migratory versus resident movements depends on resource predictability and the associated costs and benefits of tracking resource availability versus remaining in a familiar range. Here, we use 21 years of GPS data from seven populations (n = 239) of pronghorn (Antilocapra americana) and 12 populations (n = 283) of elk (Cervus canadensis) across Wyoming, USA to test if resource-based hypotheses predict individual movement strategies within a common geographic range. We identified three distinct movement strategies in each species—residents, dual-range migrants and multi-range migrants. Spatiotemporal variation in resources did explain variation in strategies in both pronghorn and elk, with residents experiencing less spatial and greater year-to-year variation than migratory individuals. However, spatiotemporal variation did not predict differentiation between dual- and multi-range migrants in either species. Climatic conditions were also important, especially in elk, where individuals were less likely to be resident when they experienced worse winters. Our findings demonstrate that the movement strategies of temperate ungulates are consistently linked to spatiotemporal resource variation across scales, but additional mechanisms can also facilitate localized behavioural differences.