Reproductive and agonistic interactions mediated by multimodal signals of a Neotropical torrent frog

Frogs primarily mediate their intraspecific social relations through acoustic signals, but other communication modes such as chemical, seismic, and visual cues are also used. When signals from different channels are emitted together or alternated, they create a multimodal form of communication that serves to enhance, complement, or convey crucial information. This holds particular significance for species inhabiting noisy environments, such as members of the Hylodidae family, which comprises species that dwell in rivers and streams (rheophilic frogs) and exhibit a diverse behavioral repertoire, including acoustic, visual, and tactile signals. In this natural history study, we observed a Hylodes heyeri population, documenting their reproductive and agonistic interactions among individuals. The H. heyeri social interactions are mediated by acoustic, visual, and tactile stimuli, in a multimodal context. We reported the use of four different visual signals – arm and leg lifting, leg stretching, and toe flagging. Most males exhibited aggressive behavior when intruder males entered their calling area and demonstrated site fidelity for consecutive days. Although diverse, their behavioral repertoire is still less extensive than that of congeneric species, and it is likely that a more comprehensive study would reveal a richer communication system. In spite of that, these observations contribute to filling a gap in our understanding of the multimodal communication of Hylodes species.