GRILLIOT, Matthew E. ; MENDONCA, Mary T.*; BURNETT, Stephen C.; Auburn University, Auburn; Auburn University, Auburn; Clayton State College and University, Morrow: Sexual Dimorphism in the Ultrasonic Signals of Big Brown Bats in the Mating Season

Investigating the communicative function of ultrasonic signals in a social context provides valuable insight into one of the most sophisticated communication mechanisms utilized by any species. In many animal species, ultrasonic signals are used in intraspecific and interspecific communication for a variety of social purposes (Sales and Pye 1974). Bats are well known for their use of ultrasound for navigation and foraging. However, few studies examine bat ultrasound in a social context, and none conclusively demonstrate a role for ultrasonic communication in bat courtship and mating. We have a captive colony of big brown bats housed in environmental chambers that allow us to alter temperature and photoperiod in order to mimic seasonal changes and induce mating behavior. This offers us a unique opportunity to investigate potential sex differences in ultrasonic signals used for courtship and mating and those used for echolocation. In the reproductive season, we recorded the echolocation signals of 20 adult male and 20 adult female big brown bats on tether lines in the field. We compared these signals to previously collected data of ultrasonic signals used in courtship and mating. We show that the ultrasonic emissions of big brown bats are sexually dimorphic when used for courtship and mating, but not when used for echolocation. This provides evidence for the role of ultrasonic communication in courtship and mating behaviors in the big brown bat.