GORDON, N.M.*; GERHARDT, H.C.; HELLMAN, M.L.; TEGTMEYER, C.G.; University of Missouri, Columbia; University of Missouri, Columbia; University of Missouri, Columbia; University of Missouri, Columbia: Conspecific acoustic signals influence ovarian development and hormonal levels in female gray treefrogs (Hyla versicolor).

Conspecific acoustic signals can act as cues regulating reproduction in vertebrates. We tested the hypothesis that females of the gray treefrog, Hyla versicolor, respond to conspecific male signals by increasing the extent of ovarian development and adjusting the steroid hormone levels that regulate this development. Gray treefrog females that had recently oviposited were exposed to playbacks of either 1) filtered pink noise or 2) conspecific calls for the duration of a breeding season (nine weeks in 2005). Ovarian morphology was then monitored weekly by candling frogs and examining changes in ovarian development. Samples of blood plasma were taken for steroid analysis as ovarian changes were observed. We found that H. versicolor females exposed to conspecific calls develop new follicles more rapidly and reabsorb unused follicles more slowly when compared to frogs exposed to filtered pink noise (p<0.0001). Additionally, changes in ovarian development reflected changes in hormonal levels, with estradiol levels increasing as the ovaries enlarged. Our findings suggest that female H. versicolor exposed to conspecific calls may be more likely to return sooner to a breeding chorus for oviposition than would females that are not exposed to these sounds. The stimulated females are thus more likely to produce a second clutch during the breeding season, potentially improving an individuals’ annual reproductive fitness. Previous work on anuran acoustic communication has emphasized the role of male calls in sexual selection and male-male competition. Our results provide support for a third function of male calling behavior: stimulating female reproductive development.