Temperature-dependent consumption of spiders by little brown bats (Myotis lucifugus), but not northern long-eared bats (Myotis septentrionalis), in northern Canada

Abstract

Intraspecific variation in diet has been observed in many species, including the geographically widespread little brown bat (Myotis lucifugus (Le Conte, 1831)). Spider consumption by M. lucifugus is more common in northern regions of their distribution, possibly due to reduced availability of aerial prey during low temperatures. However, in previously studied northern regions, M. lucifugus was the only bat species captured. The purpose of our study was to examine whether there is overlap in the diet and morphology of M. lucifugus and the northern long-eared bat (Myotis septentrionalis (Trouessart, 1897)), a species that commonly gleans prey, in the Northwest Territories, Canada. There were significant differences in the dietary composition and wing morphology of the two species, suggesting partitioning of resources. Both species consumed spiders, although unlike M. septentrionalis, the probability of M. lucifugus consuming spiders was significantly greater at low temperatures. Myotis lucifugus demonstrated a different pattern of spider consumption than in other northern regions where it consumes spiders throughout the summer, suggesting the possibility of resource competition where M. lucifugus overlaps with M. septentrionalis. Further research is needed to determine whether arthropods are seasonally limiting at high latitudes and to examine how these species capture nonaerial prey, including spiders.