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Just like Navy engineers who jam the sonar of enemy ships, bats can jam the signals of other bats to ward off competition for food, a new study finds.
Bats hunt by echolocation, which means they emit high-pitched sounds and listen to the echoes that bounce off their prey. But competition for food can be fierce, and Mexican free-tailed bats emit a special call that can interfere with the sonar of other bats that are pursuing a meal.
"They get into amazing aerial dogfights," said William Conner, a biologist at Wake Forest University in Winston-Salem, North Carolina. "One will jam the other, and the other will jam back." [See video of bats emitting jamming signals]
Conner and his colleague Aaron Corcoran studied Mexican free-tailed bats using high-speed cameras and microphone arrays. Corcoran was examining the interaction between the bats and their prey, moths, when he noticed that the bats produced a strange sound — which they made only when another bat was homing in on the moth.
"It sweeps through the frequency range that bats use, and that’s the standard method used to jam sonar and radar," Conner told LiveScience.
Conner and Corcoran set up audio and video systems to watch as wild bats hunted tiger moths. The researchers played recordings of the jamming signals or other sounds, such as pure tones or white noise.
When a bat is about to nab its prey, it emits a "terminal buzz" that is thought to help it lock on to its meal's location. The scientists played the jamming signals both during the buzz and also at other times during the hunt. Bats that heard the jamming signal just as they were about to attack a moth were 86 percent more likely to miss. This finding supports the idea that the sounds the bats made were indeed jamming signals.
The next step is to figure out the mechanism by which the jamming signal interferes with the networks of neurons involved with echolocation. To find out, scientists would have to record the signals from the bats' brains while they're listening to the jamming sound.