Tree calls of three hylid treefrogs: Environmental triggers of calling frequency During the breeding season, males of several treefrog species emit a diurnal call that is commonly called a rain call or tree call. The mating benefit of these daytime calls broadcast from the tops of trees is unknown; they may attract distant females or advertise territories. Currently, there is no information on tree calls in any frog species. I investigated how environmental variables affect tree call frequency (number of calls per hour) of barking treefrogs (Hyla gratiosa), pinewoods treefrogs (H. femoralis) and squirrel treefrogs (H. squirella) by testing the null hypothesis that tree call frequency is unaffected by temperature, relative humidity and barometric pressure. I predicted that high temperature and relative humidity and low barometric pressure would stimulate more tree calls because they indicate impending rain that precedes amphibian breeding. Results of my study indicate that environmental parameters when tree calls were given varied among species. For example, Hyla femoralis gives tree calls at a lower mean temperature than both H. gratiosa and H. squirella, which called at similar mean temperatures. All three species preferred a different mean relative humidity at which to give tree calls; Hyla femoralis at the highest, H. gratiosa a little lower, and H. squirella at the driest. Hyla squirella also called at a lower barometric pressure than both H. femoralis and H. squirella. My results can be used to develop monitoring strategies for conservation and restoration efforts for these treefrogs and other species that give tree calls. It also provides information on the life history and mating behavior of H. femoralis, which is used as an indicator species by the U.S. Forest Service. Abstract of Kristine's oral presentation to 2005 joint meeting of the American Elasmobranch Society, American Society of Ichthyologists and Herpetologists, The Herpetologists' League and the Society for the Study of Amphibians and Reptiles, Tampa, Florida.

Kristine's thesis research: tree calls of hylid frogs