Moths Jam Bat Sonar, Throw the Predators Off Course

Matt Kaplan
for National Geographic News
July 17, 2009

Developing ultrasound blasts to disrupt enemy sonar may sound more like a submarine arms race than animal evolution. But, believe it or not, some moths have done just that to evade hungry bats, a new study says.

Bats emit high-pitched cries, then listen as the sound waves bounce off nearby objects—allowing the bats to find and eat tiny insects in the dark, among other things.

(Related: "Early Bats Flew First, Developed 'Sonar' Later.")

Yet bats aren't the only ones making waves.

Some tiger moth species make ultrasonic clicks with their bodies.

"These clicks were puzzling to us, because we did not know if they were being used to startle attacking bats, warn the bats that the moths tasted bad, or somehow confuse the bats by jamming their sonar," said study co-author William Conner, a biologist at Wake Forest University.

To find out, Wake Forest research team had so-called big brown bats hunt tiger moths in a chamber fitted with ultrasonic recording equipment and high-speed infrared video.

If the moth sound is used to startle bats, then in the chamber the bats should be disrupted on first attack, then learn to ignore the ultrasonic click, the team figured.

That didn't happen.

If the moths' clicks are warnings that the insects taste bad, then the bats should hear the click, bite the moth—and never do so again whenever they hear the sound.

That didn't happen either.

Instead, the bats regularly missed the moths when the ultrasonic clicks were emitted—proof, the team says, that moths have evolved a way to jam bat sonar.

(See bat pictures from National Geographic magazine.)

Findings published in today's issue of the journal Science.

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