For a long time, it has been known that microbats use echolocation, or sonar, to determine where objects are, to help them navigate and hunt. Echolocation involves transmitting a high pitched call and then using the sound transmitted back- in the form of an echo- to pinpoint where objects are. Bats use this to locate their prey and once they have found food, they will emit a fast paced ‘feeding buzz’ before swooping in to take the meal.
For the first time ever, recent research shows that one bat species, the mexican free-tailed bat, Tadarida brasiliensis, actually uses its echolocation to block the signal of other bats during feeding so they can sneak in to steal the meal, which is a fascinating example of intraspecific food competition.
Aaron Corcoran was studying the Grote’s tiger moth, Bertholdia trigona, and it’s ability to jam the sonar of the big brown bat, Eptesicus fuscus, whilst being hunted. Whilst carrying out this research, he discovered that one call of the mexican free-tailed bat was very similar to the sound emitted by the tiger moth whilst jamming the big brown bats signal and decided to investigate the mexican free-tailed bat further, with the help of William Connor. Whilst carrying out this research, Connor and Corcoran found that the mexican free-tailed bat did indeed emit a strange sound when one bat was about to have a successful hunt:
“It sweeps through the frequency range that bats use, and that’s the standard method used to jam sonar and radar,” Conner told LiveScience.
Connor and Corcoran used video and audio equipment to record wild mexican free-tailed bats and then used the recordings to play back to the bats to see how they were affected. They played the jamming signals back, along with other signals, during the feeding buzz of bats and at other times during the hunt. The evidence showed that the jamming signal only really affected the bats when it was played back during a feeding buzz and the figures show that a bat that hears the jamming signal during a feeding buzz is 86% more likely to miss the meal.
With this evidence, the study concluded that mexican free-tailed bats can indeed block each others signal whilst hunting and that they choose an optimum time to to do this- just as the first bat emits its feeding buzz and swoops for the meal, the second bat sends the jamming signal, causing the first bat the lose its bearing and the second to be able to swoop in and steal the food.
The full study ‘Bats jamming bats: Food competition through sonar interference’ can be found online in the Science Journal here: http://www.sciencemag.org/content/346/6210/745.
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