Meeting Abstract
Whether differences in hormone levels among males that alternate between mating tactics are a cause or a consequence of tactic expression is central to understanding the mechanisms regulating such behavioral decisions. This issue is particularly relevant in anuran amphibians where males switch between being callers or non-calling “satellites” because the social acoustic environment can mediate changes in both tactic expression and hormone levels. Hence, it is not clear whether males adopt different tactics in response to rival male signals, hormone levels, or both. We previously showed that acoustic signals produced by male green treefrogs, Hyla cinerea, can increase corticosterone (CORT) and decrease androgens in male signal receivers. These changes result in hormone levels similar to those found in satellite males in natural choruses. We now combined vocal playback experiments with measurement of circulating hormone levels. In response to vocal playbacks, 24% of calling males adopted a satellite tactic. These males previously produced less attractive calls than males that continued to call, but the two groups had similar CORT and androgen levels, suggesting that tactic decisions are based on the relative attractiveness of competing males and independent of any detectable differences in hormone levels. We then increased CORT levels in calling males to determine how acoustic stimulation of CORT production in rival males benefits male signalers. CORT injections reduced vocal attractiveness and induced satellite behavior. Thus, signal quality and hormone levels both can play a critical role in tactic decisions and different hormone levels in callers and satellites can be both a cause of tactic expression and a consequence of interacting with callers after adopting the satellite tactic.
