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In the túngara frog, Physalaemus pustulosus, males alter calling behavior with changes in their social environment, adding ‘chucks’ to their advertisement calls in response to the calls of conspecific males. Other studies demonstrate that adding chucks increases the attractiveness of calls to females but also increases the risk of bat predation. In the current study, subcutaneous injections of the neuropeptide hormone arginine vasotocin (AVT) significantly increased chuck production in male túngara frogs. The effects of AVT on chuck production did not depend on the presence of playback stimuli, suggesting that AVT increased either the males’ general motivation to produce chucks or their responsiveness to the calls of distant males. Injections of AVT also increased the probability that males would call and decreased the latency to call after injection, supporting the hypothesis that AVT influences motivation to call. Finally, AVT inhibited a drop in call rate after the termination of a playback stimulus and increased call rate at a lower dose of AVT. The effects of AVT on chucks and call rate appear to be independent of each other, as there was no correlation between change in chuck production and change in call rate in individual males. We conclude that AVT may play an important role in socially-mediated call changes that result from competition for mates. The behavioral changes induced by AVT might increase a male’s attractiveness to females, and also may be consistent with an aggressive response to another túngara frog male.

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Aggression can have a critical impact on the functioning of societies. Some aspects of aggression have received considerable attention, such as links between parenting behavior and offspring aggression in humans. Although acknowledged as being important to the understanding of human aggression, animal aggression has been relatively unstudied. Recent mammalian animal research is emerging that addresses issues relevant to the study of parenting and aggression. This has been accomplished primarily by focusing on nontraditional mammalian model systems. We integrate human and nonhuman animal studies to (a) further elucidate the potential impact that the behaviors of fathers have on offspring aggression, (b) study the influence of paternal behavior on the behavior of offspring and transfer of aggression across generations, and (c) explore neural and physiological underpinnings for variation in paternal behavior and aggression.

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