Meeting Abstract

S3.9  Sunday, Jan. 4  Hormonal regulation of vocalization in anuran amphibians: insights from toads with alternative mating tactics LEARY, C.J.; University of Utah leary@biology.utah.edu

Despite the long history of anuran amphibians as models in physiology and acoustic communication, relatively little is known about the relationships between circulating hormone levels and vocal performance. In this presentation, I will present data on hormone-vocal relationships in two toad species, Bufo woodhousii and B. cognatus, that conditionally alternate between calling and non-calling mating tactics. In both species, high levels of corticosterone (CORT) suppress vocalization and elicit the adoption of the satellite mating tactic. In the former species, CORT level does not appear to alter various call parameters important in mate selection. In B. cognatus, however, CORT administration experiments indicate that, prior to cessation of vocalization, there is a progressive decrease in call duration as CORT levels increase. This effect of CORT on call duration also influences interactions among males in natural choruses; calling males with associated satellite males have lower levels of circulating CORT and longer calls than calling males without satellites. Satellite males thus appear to maximize their chances of intercepting mates by associating with those calling males that are also preferred by females. Attractive males with low levels of circulating CORT may, however, experience a decrease in mating success by attracting satellite males. In none of these studies could the behavioral changes be attributed to changes in androgen levels, as has been predicted by recent models for the regulation of vocal performance in anuran amphibians. These results highlight that stress hormones like CORT can have considerable influence on male traits important for sexual selection.