Vasotocin induces sexually dimorphic effects on acoustically-guided behavior in a tropical frog.

The neuropeptide arginine vasotocin (AVT) promotes sexual advertisement and influences vocalization structure in male anuran amphibians. In the present study, we used wild túngara frogs (Physalaemus pustulosus) to investigate the effects of AVT on phonotaxis in males and females-thereby controlling for potential task differences between the sexes. Using a combined within- and between-subjects design, we showed that acoustic choice behavior in female frogs is not influenced by injection per se (vehicle) or by AVT. Latency to choice in females, however, tends to decrease after AVT injection, supporting the hypothesis that AVT promotes female sexual arousal. In contrast, male choice behavior and latencies are negatively impacted by injection (vehicle) but rescued to pre-injection levels if administered with AVT. The sexes differed in area restricted searching (ARS) following choice-a measure of locomotor perseverance-with females but not males exhibiting ARS. AVT did not influence ARS behavior but ARS frequency was positively associated with the attractiveness of the acoustic stimulus. Finally, we showed that a female's latency behavior is correlated with her partner's behavior. Collectively we show that AVT promotes phonotaxis in both sexes in a dimorphic manner-a result that is consistent with sex differences in the neural vasotocin system.