Bats in a noisy landscape: ecological and behavioural effects of anthropogenic noise disturbance

Anthropogenic noise is an increasing ecological problem, causing animals to alter their behaviour in various ways. Foraging constitutes a major daily activity for many animals, but foraging ability under noisy conditions has surprisingly been largely overlooked. Among these animals are the bats (Chiroptera), which represent an important mammalian group, both ecologically and in terms of species numbers. The aim of this proposal is to elucidate the effect of anthropogenic noise on foraging behaviour in insectivorous (echolocating) bats. I outline a series of field and laboratory experiments that will contribute to the understanding of how anthropogenic noise affects bats’ foraging abilities, as well as the underlying mechanisms. In experiment 1, I test the effect of different noise treatments (silence, traffic noise, and white noise) on foraging activity of bat assemblages in a natural setting at several distances to the noise source. I expect noise to negatively affect foraging activity, with a decreasing effect with distance from the sound source. In experiment 2, I test captive brown long-eared bats (Plecotus auritus) for their foraging capacity under similar noise treatments, using either hearing-impaired or non-impaired moths as their prey, to elucidate whether the bats, the moths, or both are affected by noise; different scenarios are discussed for this experiment. In experiment 3, I test the ability of brown long-eared bats to use foraging-related public information under noisy and silent conditions in a laboratory experiment, and expect impaired abilities under noisy conditions. In experiment 4, I use a captive but outdoor population of common pipistrelle bats (Pipistrellus pipistrellus) to test whether chronic daytime noise exposure affects foraging activity and stress levels in these bats, and expect relative foraging activity to decrease and stress hormone levels (as a proxy for stress levels) to increase upon onset of noise; noise-induced effects are expected to diminish gradually with time due to habituation. In the final experiment, I test whether experimentally enhanced stress levels (simulated by a glucocorticosteroid hormone injection) indeed affect foraging activity in pipistrelle bats, and predict that relative foraging activity decreases upon administration of stress hormones. The experiments described here will provide novel insight into how anthropogenic noise affects foraging behaviour in an internationally protected and ecologically important taxonomic group