A dopamine agonist affects the social decision-making of calling male túngara frogs

When vocalizing, many animals engage in decision-making processes that integrate information regarding the current social context. The midbrain dopaminergic system may provide a conserved mechanism underlying this process. For instance, in songbirds, modulation of dopamine release appears to contribute to social context-dependent changes to song. However, relatively little is known about the degree to which dopamine may contribute to similar vocal production and decision-making processes in other taxa, particularly the highly vocal anurans (frogs and toads). Here, we treated wild-caught male túngara frogs (Engystomops pustulosus) with a general dopamine agonist (apomorphine) and assessed its effects on motor performance and motivation as well as vocal decision-making in response to auditory stimuli that varied in social relevance. We found that the dopamine agonist generally increased vocal speed, with decreases in response latencies and call durations. Additionally, we found that dopamine increased call complexity, but only in response to the most socially relevant auditory stimulus (conspecific call). Finally, dopamine treatment and auditory stimulus interacted to affect decision-making regarding call timing and overlap with the stimulus. Compared to controls, frogs with apomorphine were more likely to overlap the playback stimulus in a manner predicted to be more attractive to females. These results highlight a role of dopaminergic circuits in modulating vocal outputs based on social inputs within a species of basal tetrapod.