Hunting in a Mechanized World

We've always imagined bats to use echolocation in a quiet neighborhood to locate their next meal with pinpoint accuracy, but how well can they find their prey in a noisy and unnatural environment? In a recent study by Björn Siemers from the Max Planck Institute for Ornithology in Germany, Siemers tests to see if bat's hunting abilities are impaired by man made noises.

Siemers and his colleagues let a group of young male greater mouse-eared bats to forage for worms in a soundproof room divided into two equal parts. The bats spent an equal amount of time foraging in both areas of the room, locating their meals with ease, but with the presence of white noise in one half of the room, the bats spent over 80% of their time foraging in the quieter environment. Siemers next introduced a recording of a highway to one of the divided rooms. The bats were significantly less bothered by the highway noise, spending almost 40% of their time in the "highway" environment, and were still able to find their prey with precision. Oddly enough, the bats had a much more difficult time locating their quarry in a naturally made sound of rattling reed beds, a noise they may naturally encounter daily.

Although not completely sure how the bats are affected by man made noises, Siemers hopes his work will help build a more friendly environment to help protect these endangered species.

The full article can be found here.

Posted by Dan Hong (3)


Update:

Although not mentioned in the article, the greater mouse-eared bats are a European species. Their habitat generally lies near human settlements. They are currently in the status of endangered, and considered to be extinct within the United Kingdom.

White noise is simply a power density within a fixed bandwidth of a frequency. The greater mouse-eared bat uses echolocation with a frequency ranging from 22-86kHz. If a white noise were to be played within the range of these bat's echolocation frequency, it would be a disturbance, and their performance in locating prey could possibly be hindered. Man made noises, and possibly that of highway noises, would have a lower frequency than the frequency used for echolocation, which is a possible reason why these bats were not affected by the highway recordings.