Roosting Behaviour and Thermoregulation of the Northern Long-Eared Bat (Myotis septentrionalis) Near the Northern Extent of its Range

Abstract

Reproductive female mammals have high energetic demands. This may be particularly true for small, nocturnal mammals at high latitudes, where temperatures are relatively low and summer nights are short. Tree roosts are colder than building roosts, likely resulting in greater energetic constraints for tree-roosting bats. My research goal was to determine how reproductive, tree-roosting Myotis septentrionalis reduce the costs of roosting in relatively cool roosts near the northern extent of their range. I investigated the roosting behaviour of M. septentrionalis, and the thermoregulatory patterns and reproductive timing of M. septentrionalis and building-roosting M. lucifugus in the Northwest Territories, Canada. Myotis septentrionalis exhibited roosting behaviours that should reduce energetic costs. Despite lower tree-roost temperatures, the two species used similar thermoregulatory patterns, suggesting higher energetic costs for M. septentrionalis. However, M. septentrionalis foraged for longer, perhaps compensating for these higher costs, resulting in similar reproductive timing and rates between species.