Bats produce longer, louder calls when traveling among lots of other bats. Photo Sarun T / Shutterstock

TEL AVIV, Israel, Dec. 24 (UPI) -- New research shows bats produce longer, more intense echo-location calls when flying in large groups, surrounded by the noise of other bat calls.

Scientists have previously theorized that bats change the frequency of their call to identify it among the noise created by their peers, but the hypothesis had never been tested.


To figure out how bats echo-locate in a crowd, researcher at Tel Aviv University trained several bats to fly to a roost on command. Speakers placed near the roost pumped out bat calls to mimic the presence of different sized groups of bats.

Their experiments showed bats compete with "severe interference," or excessive crowd noise, by lengthening their calls and producing more intense calls -- the more bats, the longer and more intense the call.

Scientists found no evidence that the bats shift the tone, or frequency, of their call in order to navigate among company.

"Results suggest that the bats' response aimed to increase the signal-to-noise ratio and not to avoid spectral overlap," researchers wrote in their study, published this week in the Proceedings of the Royal Society B.