SCHAD, KM*; FAUTH, JE; Univ. of Central Florida, Orlando; Univ. of Central Florida, Orlando: Tree call of treefrogs: more than just rain calls

During the breeding season, males of several treefrog species give diurnal vocalizations that are commonly called rain calls or tree calls. The mating benefit of calling 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. We tested the null hypothesis that tree call frequency (number of calls per hour) of barking treefrogs (Hyla gratiosa), pinewoods treefrogs (H. femoralis) and squirrel treefrogs (H. squirella) is independent of temperature, relative humidity and barometric pressure. We predicted that high temperature and relative humidity and low barometric pressure would stimulate tree calls because these environmental variables indicate impending rain that precedes amphibian breeding. Our results indicate that environmental and temporal parameters associated with tree calls varied among species. For example, Hyla femoralis gave tree calls at a lower mean temperature than both H. gratiosa and H. squirella, which called at a similar mean temperature. 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. H. squirella called at a lower barometric pressure than both H. femoralis and H. gratiosa. Hyla femoralis called more often from 0600-0800 h and H. gratiosa peaked from 0800-1000 h; whereas H. squirella called more frequently from 1600-1800 h. Our results indicate that these tree calls are more than simple indicators of rain or good breeding conditions, and may be advertisement calls. Our results can be used to develop monitoring strategies for conserving and restoring populations of treefrogs and other amphibian species that give tree calls.