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20 December 2023 Visual Signals Are Not Performed More Frequently by Nocturnal Treefrogs in Naturally Noisier Environments
Raíssa Furtado, Sabrina P. Santos, Fausto Nomura
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Natural selection favors signals that maximize information transfer relative to background noise, reducing signal and/or information degradation. When background interference is unavoidable, multiple signals can arise, sending redundant information to ensure proper communication. Herein, we test the hypotheses that visual signaling in anurans can be an alternative to (H1a) or a reinforcement of (H1b) acoustic signaling when communication occurs in naturally noisier environments. If H1a is correct, we expect that an increase in background noise level will result in a decrease in call rates coupled with in an increase in visual displays. Alternatively, if H1b is correct, we expect an increase in visual displays without reducing call rates. To test these predictions we counted the visual and acoustic responses of male anurans exposed to artificial models constructed to simulate a conspecific male intruder. These counts were correlated with the sound pressure level of the environment where the experiments were conducted. We tested three nocturnal treefrog species, one that reproduces in fast-torrent streams (Bokermannohyla sapiranga) and two that form choruses (Boana albopunctata and B. goiana). The rate of call emission was not influenced by the background noise level. Despite the observed diversity of visual displays (limb lifting, face wiping, toe/finger trembling, upright posture, vocal sac display, head bobbing), only the emission of face wiping displays by males of B. sapiranga was correlated with background noise, but it was reduced with the increase of the background noise level. Thus, we did not find empirical support for our hypotheses, which suggests that these species might be fully adapted to the natural noisy background variation from where they breed.

Raíssa Furtado, Sabrina P. Santos, and Fausto Nomura "Visual Signals Are Not Performed More Frequently by Nocturnal Treefrogs in Naturally Noisier Environments," South American Journal of Herpetology 29(1), 1-9, (20 December 2023).
Received: 6 October 2020; Accepted: 2 April 2023; Published: 20 December 2023
background noise
Boana albopunctata
Boana goiana
Bokermannohyla sapiranga
multimodal communication
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