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Crickets Craft Tools Out Of Leaves To Make Their Mating Call Louder, Scientists Say

(SOUNDBITE OF CRICKET CHIRPING)

AILSA CHANG, HOST:

Male tree crickets advertise their availability by rubbing their wings together to chirp. And larger, louder males find more favor with the females.

MARY LOUISE KELLY, HOST:

But smaller, less desirable males do have a trick to juice up their prospects - they amplify their chirps by punching a hole in a leaf and sticking their head through it. Rittik Deb of India's National Center for Biological Sciences described it like this.

RITTIK DEB: You know those collars that they put on dogs when they're putting some vaccine or something on the dogs? It looks something like that.

CHANG: This technique, known as baffling, can more than double the volume of a cricket's mating call. Ed Baker of the Natural History Museum in London says the leaf works sort of like a loudspeaker.

ED BAKER: You effectively increase the size of the wing, which makes the sound appear to be louder.

KELLY: Here are two recordings - same cricket. First, without the leaf.

(SOUNDBITE OF CRICKET CHIRPING)

CHANG: All right, now with the leaf.

(SOUNDBITE OF CRICKET CHIRPING)

CHANG: Whoa. I got to turn down my headphones now.

(LAUGHTER)

KELLY: This phenomenon was first documented in the mid-1970s. But what Deb's team found is it has real consequences for small crickets. His team estimates quieter males can go from zero dates a night to three simply by cranking the volume of their calls up to about 11.

CHANG: And once female crickets are reeled in, they hang around longer, too, which gives smaller males a better chance at passing on their genes. The results were published by the Royal Society.

KELLY: A question, though - if baffling works so well, why don't all crickets use it? Deb says loud males don't have much to gain.

DEB: The loud males are already getting the optimal number of mates they can mate with within a night.

CHANG: (Laughter) And though we might think of primates or crows as the smart tool-using animals, Deb says crickets deserve some credit, too.

DEB: The have the tiniest of all the brains that is possible, and yet they produce such complex behaviors.

CHANG: The chance of finding a mate, it seems, is all it takes to turn crickets into audio engineers.

(SOUNDBITE OF THE MIDNIGHT SONG, "YOUTH") Transcript provided by NPR, Copyright NPR.