Investigating Flexible Migration in Hudson Bay Woodland Caribou (Rangifer tarandus caribou)

Abstract

Facultative migration has been hypothesized as a strategy to optimize energetic gain in response to environmental fluctuations. The forest-tundra and forest-dwelling ecotypes of Ontario woodland caribou (Rangifer tarandus caribou) are often presumed to differ in migratory strategy, however their potential for facultative migration has yet to be explored. Understanding the inherent variation of migration could help improve habitat management. We compared GPS telemetry-based movement data from 109 radio-collared caribou across northern Ontario with estimates of vegetation, snow cover, and human disturbance to identify environmental drivers associated with migration. We also evaluated whether caribou exhibited a migratory syndrome, using measures of selection and movement in comparison with movement strategies. We found evidence of facultative migration from both ecotypes, with little evidence of an overlying migratory syndrome. Both probability and distance of migration were positively correlated with snow, while only probability increased with vegetation. Plasticity in migration may suggest resilience to change.