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Biology
Completed Project

Effects of Deer Browsing on Sound Propagation in Northeastern Temperate Forests

Timothy Boycott, Vassar College ’16, Jingyi Gao, Vassar College ’16 and Prof. Megan D. Gall
White-tailed deer density in the northeast has steadily increased over the past 100 years. This increased density has led to greater impacts of deer on the vegetation structure of native habitats. These changes in vegetation have implications for the ecology of many taxa. For instance, deer browsing alters the behavior of many bird species by altering foraging, roosting, and breeding habitats. However, we do not yet know what impact deer browsing may have on acoustic communication in birds, although there is a large body of literature on the effects of vegetation structure on sound propagation. Here we investigated the effects of deer browsing on sound propagation in temperate deciduous forest. We used playback experiments at the Vassar Farm and Ecological Preserve to determine whether sound fidelity and sound attenuation of three types of acoustic stimuli (white noise, pure tones, and trills) would differ between deer browsed and deer excluded plots. We found that sound fidelity, but not sound attenuation, differed between habitats, with deer browsed habitats having great sound fidelity than deer excluded habitats. This difference in sound propagation characteristics between the two habitats may influence the efficacy of acoustic communication. For example, bird vocalizations are more likely to retain sound information after propagation in deer browsed habitats than in deer excluded habitats, thus potentially making communication more effective. However, the possibility of eavesdropping by predators and competitors could also be greater under such circumstances. These effects could influence the fitness of individuals or success of species by altering reproductive success or by increasing the risk of predation. Overall our results suggest a fundamental impact of deer browsing on sound propagation in temperate deciduous forest, which could have implications for acoustic communication in avian species and their broader ecology.