Meeting Abstract
Circulating hormone levels vary among males competing for mates, but how this variation affects the signaling phenotype is poorly understood. In green treefrogs, Hyla cinerea, males competing for mates engage in vocal contests that increase corticosterone (CORT) and decrease androgens in contest losers, who adopt a non-calling “satellite” mating tactic. We previously showed that CORT administration to calling males reduces vocal effort and increases the probability of satellite behavior during simulated territorial intrusions, suggesting that elevated CORT compromises vocal quality and decreases the propensity to call in a context-dependent manner. However, the extent to which these effects reflect variation in vocal behavior of males in natural choruses is unclear. Here, we examined how hormone levels, social context, body size and condition relate to vocal attributes and behavior in calling males and in satellites after removal of calling “host” males. Results revealed that satellites had higher CORT, lower androgens, were smaller, and in poorer condition than hosts. Host removal resulted in vocalization in 74% of satellites. These males invested less effort in vocalization than hosts and CORT level best explained these differences. The remaining 26% of satellites did not vocalize after host removal and had lower androgens than satellites that vocalized. Results provide support for context-dependent effects (i.e., host presence/absence) of elevated CORT on the probability of vocalization and link high CORT to reduced vocal quality. In contrast, low androgens were associated with a low probability of vocalization regardless of social context and androgen level was a poor predictor of vocal attributes.
