Gabriel Reyes

The hoary bat is a migratory, foliage-roosting bat with a mostly solitary roosting habit. Little is known about the social interactions of this species, but as a solitary roosting bat, most interactions between conspecifics are thought to involve mating behavior or territorial disputes. Developing a more complete understanding of the social behavior of this species may provide critical insight to reduce and manage the high fatality rates from wind turbines during the fall migration and mating season. I tested the response of hoary bats to conspecific social call playback during the spring and fall migration to: 1) test whether conspecific social call broadcasting attracts or repels individual bats; 2) examine whether there are seasonal differences in these responses; and 3) describe the structure and variation of recorded social calls. I conducted trials along migration routes in New Mexico, during the spring northward migration, and California, during the fall southward migration. Hoary bats were attracted to social call broadcasting during both the spring and fall migration. A lack of females detected at study sites precluded the determination of sex-specific responses. Hoary bats used these calls during the spring migration, when only males were present, suggests a social function not associated with mating. While calls were variable in frequency and length, there was no evidence of distinct syllables or types of calls. Conspecific call broadcasting can be used as an acoustic lure to aid in capturing hoary bats, and can thus assist subsequent investigations of this extremely elusive and difficult to study species.