Social regulation of androgenic hormones and gestural display behavior in a tropical frog

Many animals use forms of gesture and dance to communicate with conspecifics in the breeding season, though the mechanisms of this behavior are rarely studied. Here, we investigate the hormone basis of such visual signal behavior in Bornean rocks frogs (Staurois parvus). Our results show that males aggregating at breeding waterfalls have higher testosterone (T) levels, and we speculate that this hormone increase is caused by social cues associated with sexual competition. To this end, we find that T levels in frogs at the waterfall positively predict the number waving gestures-or foot flags-that males perform while competing with rivals. By contrast, T does not predict differences in male calling behavior. In these frogs, vocal displays are used largely as an alert signal to direct a rival's attention to the foot flag; thus, our results are consistent with the view that factors related to reproductive context drive up T levels to mediate displays most closely linked to male-male combat, which in this case is the frog's elaborate gestural routine.

Automated summary

Many animals use forms of gesture and dance to communicate with conspecifics in the breeding season. This study focuses on the hormone basis of visual signal behavior in Bornean rocks frogs. The results indicate that the aggregation of males at breeding waterfalls leads to higher testosterone levels, which may be caused by social cues related to sexual competition. The study also finds that testosterone levels positively predict the number of waving gestures while competing with rivals, but do not predict differences in male calling behavior.