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First published online September 19, 2008
Journal of Experimental Biology 211, 3174-3180 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.022863
Foraging bats avoid noise
1 Zoological Institute, Department of Animal Physiology, University of
Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
2 Max Planck Institute for Ornithology, Sensory Ecology Group,
Eberhard-Gwinner-Strasse, 82319 Seewiesen, Germany
* Author for correspondence (e-mail: siemers{at}orn.mpg.de)
Accepted 14 August 2008
Ambient noise influences the availability and use of acoustic information in animals in many ways. While much research has focused on the effects of noise on acoustic communication, here, we present the first study concerned with anthropogenic noise and foraging behaviour. We chose the greater mouse-eared bat (Myotis myotis) as a model species because it represents the especially vulnerable group of gleaning bats that rely on listening for prey rustling sounds to find food (i.e. `passive listening'). In a choice experiment with two foraging compartments, we investigated the influence of background noise on foraging effort and foraging success. We tested the hypotheses that: (1) bats will avoid foraging areas with particularly loud background noise; and (2) the frequency–time structure of the noise will determine, in part, the degree to which it deters bats. We found a clear effect of the type of noise on the allocation of foraging effort to the compartments and on the distribution of prey capture events. When playing back silence, the bats made equal use of and were equally successful in both compartments. In the other three treatments (where a non-silent sound was played back), the bats avoided the playback compartment. The degree to which the background noise deterred bats from the compartment increased from traffic noise to vegetation movement noise to broadband computer-generated noise. Vegetation noise, set 12 dB below the traffic noise amplitude, had a larger repellent effect; presumably because of its acoustic similarity with prey sounds. Our experimental data suggest that foraging areas very close to highways and presumably also to other sources of intense, broadband noise are degraded in their suitability as foraging areas for such `passive listening' bats.
Key words: environmental noise, anthropogenic noise, traffic noise, foraging, road ecology, Myotis myotis, gleaning bats, passive listening, echolocation, masking
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K. Phillips BATS PICK UP RUSTLES AGAINST HUMAN NOISE J. Exp. Biol., October 1, 2008; 211(19): i - ii. [Full Text] [PDF] |
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