Using Hydrogen Isotopes to Assign Origins of Bats in the Eastern United States

Abstract

Stable hydrogen isotopes (dDs) in metabolically inert tissues such as feathers and hair provide a set of endogenous markers that may be useful for establishing migratory connectivity in animals. We tested the assumption of a clear relationship between dD values of growing-season–weighted average precipitation (dDp) derived from 2 geographic information system (GIS) models or latitude (LAT) and dD values in bat hair (dDh), and examined intra- and interspecific variation in dDh of 4 bat species in the eastern United States. We analyzed 251 hair samples from 1 long-distance migrant (eastern red bat [Lasiurus borealis]) and 3 regional migrants (Indiana bat [Myotis sodalis], northern long-eared bat [M. septentrionalis], and little brown bat [M. lucifugus]) captured during the reproductive period (pregnancy and lactation) when bats are resident. LAT explained more of the variation in dDh than dDp derived from either of the GIS-based models, although 1 model of dDp performed better for some species. We found significant intraspecific differences in the relationships between dDh and LAT and between dDh and estimates of dDp derived from Bowen et al. (dDpB) for L. borealis, and significant variation in the regression equations of dDh and LAT and dDh and dDp among species for adult females and adult males. Stable hydrogen isotope analysis may be a valuable tool for studying migratory connectivity in bats, but significant intra- and interspecific variatio ni ndDh values suggests that pooling across sex and age categories and use of surrogate species should be avoided.