The loss of visual and acoustic information affects the behaviour of Boana albopunctata and Dendropsophus cerradensis (Anura Hylidae) during territorial interactions

Acoustic and visual communication play a crucial role in anurans’ behaviour, but environmental interference, from natural or anthropic sources, can directly impact the quality of signals and affect the outcome of intra-specific interactions. In this study, we tested the hypotheses (1) that the degradation of a visual signal elicits increases in the receiver’s aggressiveness as a coping strategy that generates a supranormal rate of emissions, and (2) degradation of the stimulus acoustic leads to a shift toward visual signalling to enhance the efficiency of the information transfer. To test these hypotheses, we conducted an in situ experiment using two treefrog species, Boana albopunctata and Dendropsophus cerradensis. We simulated a territory intrusion by a conspecific male by displaying visual (mirror experiment) and acoustic signals (playback experiment). We designed a gradient of signal interference of 0, 25, 75 and 100% by covering the mirror with a green tape and by masking the audio playback with white noise. We performed a Generalised Linear Mixed Models, using the treefrog’s behavioural rate of emission as the response variable, the treatments as a fixed factor (four levels: 0, 25, 75 and 100% of signal interference) and individuals as a random factor (repeated measures). Boana albopunctata increased its visual display rate (e.g. finger trembling) in response to an increase in acoustic interference, and interference in visual signals resulted in supranormal aggressive acoustic behaviour. In contrast, D. cerradensis males maintain aggressiveness when exposed to low acoustic interference but reduce them significantly under high interference, also modified spectral and temporal parameters of the call, but changes in the quantity of visual signal interference did not elicit any response. In conclusion, our hypotheses were supported for B. albopunctata, while D. cerradensis diverged from our expectations.