Signaling, intersexual dynamics and the adoption of alternative male mating behaviors in green treefrogs, Hyla cinerea

Animals which produce a sexual display and conditionally switch between alternative mating behaviors over a short time period in response to local environmental conditions provide an opportunity to study the interplay of intrinsic (physiology) and extrinsic (social environment) factors that mediate this decision. Male green treefrogs (Hyla cinerea) produce acoustic signals to attract females; however, some silent satellite males attempt to intercept females attracted to nearby calling males. Females select mates on the basis of the quality of their advertisement calls. The primary objective of my dissertation research was to determine how sexual selection, in the form of male-male competition and female mate choice, mediates the probability and conditions under which males adopt alternative mating tactics.; Satellite males appear to have intrinsic constraints on their competitive ability. These males tend to be smaller and in poorer body condition than calling males. Field observations and laboratory experiments indicate that males in poor condition produce less intense and higher frequency advertisement calls at a lower rate than similarly sized males in good condition. If these call characteristics are important for male-male competition or female choice, males in poor condition may adopt the satellite tactic because they are poor acoustic competitors.; Male frogs form aggregations where they produce advertisement calls. This chorusing behavior results in intense acoustic competition among neighbors to be detected and preferred by females. To determine whether acoustic competition mediates male mating tactic decisions, I conducted a field playback experiment in which I broadcast synthetic calls of varying frequency and intensity and observed male calling and mating behaviors. Although males that stopped calling did not produce calls of lower amplitude, significantly more of their calls were overlapped by the stimulus. Calling males unable to maintain high call rates switched to the satellite tactic, as did males with spectral components higher in frequency those of the stimulus.; Differential responses to a simulated acoustic competitor did not indicate whether mating tactic switches were mediated acoustically via male-male competition or female choice. To determine whether female mate choice preferences might be important in mating tactic switches, I conducted a series of two speaker choice experiments to determine female preferences for several call characteristics. Females strongly preferred calls produced at higher rates and calls with lower-than-average spectral components.; This study supports the hypothesis that condition-dependent sexual signaling and intersexual dynamics are important factors in conditional mating tactic adoption.