Systematic variation in the stable hydrogen isotope (δ2H) composition of fur from summer populations of two species of temperate insectivorous bats

Stable hydrogen isotope techniques are increasingly used to investigate the migratory ecology of bats. This approach relies on the presence of predictable continental scale patterns in the stable hydrogen isotope composition of bat fur (δ2Hfur). While these patterns have been demonstrated repeatedly, there is local variation in δ2Hfur and the systematic patterns of variation are not well described for many bat species. We investigated local scale δ2Hfur variation in two species of North American bats, little brown myotis (Myotis lucifugus) and eastern red bats (Lasiurus borealis) obtained at two sites in southwestern Ontario. We found systematic differences in the δ2Hfur of multiple fur samples taken from the same bat, between mothers and their dependent young, and over the course of the summer season. We found substantial differences in the δ2Hfur profiles of two species from the same location as well as between populations of the same species at different but proximate locations. Our results inform sampling protocols for future stable hydrogen isotope investigations of bat ecology.