While environmental assessments of new roads focus on the danger of habitat destruction, or bats colliding (碰撞) with traffic, the first ever controlled field experiment to investigate the impact of vehicle noise suggests the thunder of road traffic is likely to drive away bats and cause bat activity to decrease by two-thirds.
Researchers played noise recorded from the A38 dual carriage way in demon, with a "dusk average" of 26 vehicle passing per minute, in locations where different bat species flew and fed. The wild bats, including pipistrelle species, were monitored with bat detectors (探测器) placed beside, and 20 metres away, from the recorded noise.
Ultrasonic (超音速) sounds from vehicle were found to block some bat species' high-frequency echo - location calls, which they use to find insect prey (捕获物) such as moths. But more significant was that most bat species sought to avoid audible (听得见的) traffic noise.
"Just like us, bats are likely to find audible road noise an irritation, something they would prefer to avoid rather than it jamming their echo-location," said Fiona Matt hews, lead author of the paper in Environmental Pollution.
Matthews said the effect of ordinary traffic noise on bats meant that the negative impact of new roads on bat populations was likely to be more far-reaching than realized.
She said: "This is important, as it means we could expect to see negative effects continue at a considerable distance from the road. We know that lower frequency road noise travels well beyond 50 metres — the scale at which ecological impact assessments are conducted. "
Dr. Henry Schofield, from Vincent Wildlife Trust, which jointly funded the research, said: "We have raised people's awareness that bat species face barriers in the landscape that impede (妨碍) their ability to access suitable feeding areas and reduce their chances of survival. Along with habitat destruction and artificial lighting at night, this research has added road noise to the list of anthropogenic (人为的) factors reducing habitat quality for these protected species. "
