Print PageThe little brown bat, Myotis lucifugus (Chiroptera: Vespertilionidae), is an insectivorous, cave-dwelling bat common in most of North America, with populations distributed from northern Canada to the highlands of Mexico. Temperate, insectivorous bats are apex predators, important consumers of nocturnal insects, and may help control pests, such as mosquitoes. M. lucifugus, like other cave-dwelling bat species, escape the extreme physiological demands of winter by hibernating, generally in subterranean sites. However, because appropriate sites for hibernation are naturally rare, cave-dwelling bats must also migrate between summer roosts and hibernacula. The cumulative effects of emerging threats, such as white-nose syndrome and wind energy development, along with continued loss and disturbance of hibernacula, may threaten the continued viability of even large populations of M. lucifugus and other cave-dwelling bat species. Despite their critical importance, the identification and preservation of hibernacula is complicated by uncertainty in the geographic significance of individual hibernacula. Understanding the connectivity and timing seasonal movements between summer roosts to winter hibernacula is essential to predict the spread of disease, estimate potential impacts of wind-energy development and to identify and preserve critical habitat. Banding studies of bats to understand connectivity are generally limited by extremely low recapture rates and intractable statistical problems. Bats, in particular, also suffer increased morality from bands. Other extrinsic markers, such as radio and satellite transmitters, are presently limited by size and expense. Techniques have been developed to use stable isotope ratios as endogenous markers and the use of stable hydrogen isotopes has recently been applied to bat migration. Stable isotope analysis of hair samples permitted us to refine molt period estimates and the hair-precipitation relationship for stable hydrogen isotopes for M. lucifugus, and then model the provenance to M. lucifugus hibernating in mines of upper Michigan.
Results/Conclusions
Probability density surfaces of geographic catchment area for each mine indicate that provenance can be assigned with better latitudinal than longitudinal control. Development of additional probability density surfaces for other isotopes, e.g. strontium, and a priori limits on migration capability may provide better longitudinal control. This study helps identify critical habitat for M. lucifugus and also develops the experimental models needed to protect key habitats of other bat species, including the endangered Indiana myotis (M. Sodalis). Additionally, the ability to monitor bat migration will help develop environmentally responsible wind energy and provides a practical framework for predicting the spread of the lethal bat white-nose syndrome pathogen.
