Continental-scale, seasonal movements of a heterothermic migratory tree bat
M.B. Wunder (UC Denver), P.M. Cryan (USGS), C.A. Stricker (USGS)
Our aim was to infer seasonal movements of individual hoary bats to better understand their migration and seasonal distribution in North America. We analyzed the stable isotope values of non-exchangeable hydrogen in the keratin of bat hair of animals killed at wind turbine facilities from across North America. We combined isotope data with museum-based distributional information to derive relative probability density surfaces for the geographic origins of individuals. We then mapped directions and distances of seasonal movements. Results indicate that hoary bats summer across broad areas. In addition to previously suspected patterns of latitudinal migration, we uncovered evidence of regular longitudinal movement by hoary bats from inland summering grounds to more thermally stable coastal regions during autumn and winter. Hoary bats migrating through any particular area, such as a wind turbine facility in autumn, are likely to have originated from a geographically expansive summering range. Heavily used migratory routes were not readily apparent and hoary bat migration may be more facultative than previously believed. Better characterization of hoary bat migration patterns and wintering behaviors illuminates our understanding of the evolution of migration and provides context for conserving these migrants.