The foraging performance of acoustic predators like bats is impaired by the noise which humans produce. This anthropogenic noise pollution should be included in environmental impact assessments of human activities, according to German researchers Siemers and Schaub. They conducted research on the foraging succcess of mouse-eared bats under different circumstances, simulating the noisy environment of a highway.
The results show that the bats need more search time to locate their prey when getting closer to the acoustically simulated highway. In other words, it gets harder for the bats to find the large ground-running arthropods, that make only faint rustling sounds, by ear. Nevertheless it is amazing that the bats perform above chance level, when detecting and localising the faint sounds of the arthropods under the noisy circumstances so close to the ‘heavy-used’ highway. This is probably due to the fact that these acoustic predators evolutionarily are adapted to foraging under conditions with natural noise such as wind or running water.
The study provides experimental evidence that traffic noise (and probably other anthropogenic noise) degrades foraging habitat quality for acoustic predators like bats, and probably also owls, carnivores and others. Through interference with the predators sensory performance or attention, the traffic noise can reduce predation pressure. This could alter the predator-prey dynamics, which in turn could ultimately interfere with ecosystem stability. Therefore, the researchers suggest that the effect of anthropogenic noise and other sensory pollution should be part of the assessment of the environmental impact of human activities.
Though not surprising, it is unnerving to realise how disturbing human activities are for ecosystems and as a consequence for the services they provide, such as clean water, clean air, food and other lifesaving basic material. (Source: ‘Hunting at the highway: traffic noise ……’ by Siemers and Schaub, Proceedings of the Royal Society, 17.11.2010)