Meeting Abstract
Males of many anuran amphibians alternate between calling and an alternative non-calling “satellite” mating tactic. Satellite males remain in close proximity to calling conspecific males and attempt to intercept females attracted to the calling male’s vocalizations. Most studies on alternative mating tactics in anurans have focused on how the social-acoustic environment influences tactic decisions. The underlying hypothesis is that males assess the relative attractiveness of other males and adopt a satellite tactic when they are unable to effectively compete with conspecifics. However, vocal playback studies that are commonly used to address this hypothesis report considerable variation in the probability of satellite tactic expression and no such studies have shown that variation in the responses of individuals is attributable to differences in vocal attractiveness. We examined whether variation in the responses of calling male green treefrogs (Hyla cinerea) to close-range broadcast advertisement calls (simulating the approach of another male) was related to vocal attractiveness or circulating levels of corticosterone (CORT) and androgens – hormones known to affect the probability of calling behavior in anurans. Calling male H. cinerea exposed to broadcast calls either: 1) continued to produce advertisement calls, 2) stopped calling (and adopted a satellite tactic), or 3) responded with aggressive vocalizations. We predicted that males that stopped calling in response to broadcast calls would be as attractive as males that continued to call but that males that stopped calling would have significantly higher CORT levels and lower androgen levels; males that responded aggressively were expected to have the highest androgen levels. We present results from field-based experiments that test these hypotheses.
