Variation in catchment areas of Indiana bat (Myotis sodalis) hibernacula inferred from stable hydrogen (δ²H) isotope analysis

Understanding seasonal movements of bats is important for effective conservation efforts. Although female Indiana bats (Myotis sodalis Miller and Allen, 1928) have been documented to migrate >500 km, knowledge of their migratory patterns is still extremely limited. We used the relationship between latitude and stable hydrogen isotope ratio in bat hair (δ²H_hair) to estimate the north–south extent of the summer range (catchment area) of bats hibernating in 14 Indiana bat hibernacula in eight states throughout its range. Range of δ²H_hair values varied substantially among hibernacula, suggesting large differences among sites in the north–south distance travelled by bats between summer and winter habitats. In particular, hibernacula in the southern portion of the range had greater catchment areas than those in the central and northern portions of the range. Variability in movement distances among sites was not associated with the number of hair samples analyzed or colony size. Significant year-to-year variation (2007–2008 to 2008–2009) in the distribution of δ²H_hair for two sites in Tennessee was observed. Currently, hibernacula considered important for species conservation are largely determined by population size, but our results suggest that migratory diversity should also be considered.