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This Frog Hears With Its Mouth

The tiny Gardiner's frog does not possess an eardrum, but it has come up with a convenient evolutionary hack to get around that

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Most sound (99.9 percent) bounces off the frog, but the mouth captures and amplifies key vibrations needed for the frogs to pick up on one another’s croaks. Photo: R. Boistel/CNRS

The tiny Gardiner’s frog does not possess an eardrum. But it has come up with a convenient evolutionary hack to get around that. The peculiar little frog from the Seychelles uses its mouth as an echo chamber, allowing it to “hear” the vibrations produced by sound. National Geographic explains how researchers teased this system apart:

When the team added the animal’s mouth to their simulations, they found that it resonates at a frequency of 5,738 Hertz. Sounds of this frequency cause the mouth to reverberate strongly, turning it into an amplifier.

And guess what the average frequency of the frog’s call is? It’s 5,710 Hertz—roughly an F note, four octaves above middle C.

X-ray images revealed only a thin film of tissue separating the frog’s mouth and inner ear, LiveScience writes, suggesting that they lost their middle ear and eardrum to the whims of evolution at some point in time.

The frog’s mouth is not a perfect ear, however. When scientists played calls from other frogs, NatGeo writes, the Gardiner’s frog didn’t react, possibly because it couldn’t catch the vibrations of those non-F notes. 

More from Smithsonian.com:

How Did Frogs Evolve? 
An Extinct Frog Reappears in Israel 

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