Date of Award
In many anuran species (frogs and toads), males alternate between calling and a non-calling satellite mating tactic. Satellite males characteristically associate with calling males and attempt to intercept females that are attracted to the vocalizations of the calling host male. The prevailing hypothesis is that the decision to adopt a calling or satellite mating tactic is based on relative attractiveness — males are predicted to adopt a satellite mating tactic when the vocalizations of nearby males are more attractive than their own. In support of this hypothesis, previous studies have shown that satellite males can be induced to call by removing the associated calling host male. However, there is considerable variation in the responses of males in host removal experiments, suggesting that the physiological status of males may play a central role in tactic decisions. For my honors research, I investigated the role of circulating hormone levels in mediating mating tactic decisions in the green tree frog, Hyla cinerea. I performed host removal experiments wherein calling males were removed in natural satellite-caller associations. I then observed whether satellite males adopted a calling tactic or remained as non-calling males and subsequently obtained blood samples for hormone analysis. Based on recent models describing the hormonal basis for calling behavior in anurans, I predicted that satellite males would have lower levels of circulating androgens, higher levels of stress hormones, be in poorer condition, and produce calls that are less attractive than calling males. Moreover, satellite males that did not call subsequent to removal of the calling host male were predicted to have lower circulating androgen levels and higher levels of CORT than satellite males that called subsequent to removal of the calling host male. Consistent with these predictions, satellite male H. cinerea had lower levels of dihydrotestosterone (DHT), higher levels of corticosterone (CORT), were in poorer condition and invested less energy in their calls than calling host males. Satellite males that called subsequent to host removal also had significantly higher DHT levels; however, circulating CORT levels did not differ for the two groups of males. My results suggest that circulating androgen levels play a central role in mediating mating tactic decisions in H. cinerea.
Pratt, Brooks, "Hormonal and Social Factors Influencing Alternative Mating Tactic Decisions in Male Green Treefrogs, Hyla cinerea" (2016). Honors Theses. 144.