Variation in the Echolocation Calls of Little Brown Bats (Myotis lucifugus) in Response to Different Habitats

Abstract

Among different bat species, echolocation call structure varies predictably according to habitat use. Much of this interspecific variation in echolocation calls reflects the physical constraints of sound propagation and echo formation in open versus spatially complex habitats. Bats must use calls that are suitable for detecting obstacles and prey in a particular setting; thus, bats that use similar habitats and catch similar prey produce similar calls. The same can be true for variation in echolocation calls within a single species that uses a variety of habitats. I recorded the echolocation calls and habitat use of a habitat generalist bat, Myotis lucifugus in order to determine whether the echolocation calls of M. lucifugus vary predictably across habitats, and if call variation is the result of individual flexibility in habitat use and echolocation behavior. I found that M. lucifugus used calls with higher frequencies, shorter durations and steeper frequency modulation in cluttered habitats than in open habitats. This type of call is consistent with a short-range target-detection strategy whereas the lower frequencies, longer call durations and shallower frequency modulation of bats in open habitats are consistent with longer-range target detection strategies. Furthermore, radiotelemetry indicated that individuals routinely foraged in different habitats. Taken together, these results suggest that call variation across habitats is the result of individual plasticity in echolocation behavior.