Abstract:
Little brown bats are sensitive to cold winters but consistent records of roosts in interior Alaska for 30 years indicate that the range of this species expands into the subarctic. We hypothesized that the little brown bat in interior and northern Alaska has adapted to high environmental demands by shifting foraging strategies. We analyzed guano to describe prey composition by microhistology, DNA analysis, stable isotope analysis, and image fragment recognition software. Alaskan bats consumed moths and flies, which was similar to the diet of southern conspecifics. However, bats in Alaska also consumed spiders. The stable isotopes of N and C in hair from bats in interior Alaskan bats were significantly different from bats in Yukon and coastal Alaska, which indicated the use of a separate habitat through summer. We used citizen science to collect reports of bats that ranged over most of Alaska and included sightings in the Arctic during autumn. Alaskan bats stored similar amounts of body fat to southern bats in autumn but unlike southern bats that migrate over 200 km, radio tracked bats in Alaska migrated short distances (<100km) to hibernacula in human structures. Expansion of the range of the little brown bat is apparently associated with a shift in foraging behavior to include gleaning of arthropods from surfaces. Overwintering at the extremely low air temperatures in interior Alaska is unlikely. Consequently, the persistence of bats in interior and northern Alaska may be related to consistent availability of human structures.
