Researchers from Tel-Aviv University have discovered that the intensity and duration of bat calls increase when they are among crowds of other bats in order to hear themselves in the chaos, according to a news release.
Bats are known to use echolocation to locate objects in their surrounding environment and avoid collision as well as to hunt prey, but little research has been done into how they recognize their own echoes when travelling or hunting with large groups. Although some have hypothesized that bats achieve recognition by changing the frequency of their tone, no studies have yet to test this theory.
In the current study, the researchers trained numerous bats to land on a roost on command and then placed speakers connected to a source that emitted bat sounds next to the roost in order to mimic certain bat group sizes in the area. While exposing the bats to different levels of noise, they examined the tones of the bat's echolocation calls and found that they tended to increase the duration of their calls and make them more intense in the presence of higher levels of competing tones.
The researchers also found that when landing on a quiet roost, bats tended to produce short calls whereas when approaching a loud roost, they produced continuous, high intensity calls. These behaviors are likely to avoid noise jamming, which could hinder their ability to land.
Interestingly, they found little evidence of spectral shifts, which conflicts with conventional theory, and when these shifts were observed, they did not decrease the overlapping of similar tones.
The findings were published in the Dec. 23 issue of the Proceedings of the Royal Society B.
