Breeding season blues: Noise disrupts female wood frog attraction to a male chorus

Background/Question/Methods

Human-induced rapid environmental change is creating novel habitats that impose new selective pressures on native species. For example, noise created by human activities can be heard at varying levels throughout the world. This noise “pollution” can pose challenges for animals that rely on sound for survival and reproduction. Research has typically focused on the effects of noise on signaler behavior, demonstrating that many animals modify their vocalizations in noisy environments, presumably to enhance signal transmission. Less is known about the ecological impacts of noise on receivers. We explored how noise impacts the reproductive behavior of an explosive breeder, the wood frog (Rana sylvatica) in central Pennsylvania. We used field playback experiments to test the hypotheses that: a) female wood frogs are attracted to the sounds of a male wood frog chorus, and b) noise impacts this attraction. We placed individual gravid female wood frogs in the center of a circular field arena and used a single-stimulus experiment with a stratified random design to broadcast either: 1) male chorus, 2) white noise, 3) male chorus + white noise, or 4) silence, from two speakers positioned adjacent to each other outside of the arena. 

Results/Conclusions

We found that female wood frogs traveled more slowly, shorter distances, and in a more random direction when male chorus was not audible. These results suggest that noise may directly impact female wood frog fitness by impeding their travel to male breeding aggregations.