Acoustic characteristics of four frog species

<p>Human activities worldwide are increasingly releasing low-frequency noise into the environment. Anthropogenic noise imposes a novel stress for wild animals and has become an increasing global concern. Many animals have been found to mitigate noise disturbance by modifying their acoustic parameters, yet the calling behaviours of species that breed near airports have not been explored in detail, especially for amphibians. Here, we measured the environmental noise of a swamp close to the runway at Haikou Meilan Airport in China. We also recorded the calls of four anuran species that reproduce in this swamp, and we measured the sound pressure levels of each focal species. These frogs vary in their call amplitude and possess disparate spectral and temporal traits. We show that two frog species characterized by lower frequency calls increase their call frequency when an airplane takes off. Moreover, three anuran species characterized by higher call rates significantly reduce their call rates (or call efforts) in response to airplane flyby. These results suggest that animals' behavioural adaptation to human-made noise may be species specific. Because call frequency and call effort have close relationships with reproductive success, we deduce that such noise-induced behaviour adjustments may influence the fitness of taxa that depend on communication by sound.</p>