In many anuran species, males vocalize to attract females and to defend their territory. Advertisement and territorial calls provide listeners with a wealth of information about the emitting individual, and are composed of spectral and temporal components. While the former mainly depend on intrinsic characteristics of the calling male, the latter can be profoundly influenced by the surrounding environment. Noises, both natural and produced by humans, can therefore affect - and potentially  impair - anuran communication.

In order to assess the impact of anthropogenic noise on an urban population of Aplastodiscus leucopygius in Sao Paulo (Brazil), 20 adult males were recorded before, during and after exposure to a 1-minute recording of traffic noise. Recorded individuals were then captured, weighted and measured to calculate their Scaled Mass Index, a valuable proxy for the amount of energy reserves stored by the animals. 

While exposed to traffic noise, male A. leucopygius increased the interval between calls and reduced their calling activity. Shorter and less frequent calls are often observed in Anuran species exposed to anthropogenic noise, which impact the quality of communication towards potential mating partners. After the noise disturbance, however, the studied individuals increased their call rate, devoting a greater amount of energy to vocalization. While apparently beneficial, such behavior may indeed be harmful, distracting energy and resources from other important functions (such as reproduction, foraging, avoiding predators). 

In conclusion, the study soon to be published in Acta Herpetologica strongly suggests that traffic noise severely impacts vocalization in  Aplastodiscus leucopygius, both during and after the disturbance. Since the species is adapted to very silent environments, however, more research is needed to verify if similar responses are observed to natural noise and white noise

Click here to read the full manuscript!

See you in two weeks!