Frogs hear with their mouths

WASHINGTON – Some of the tiniest frogs on Earth have no middle ears or eardrums but can hear by using their mouths, scientists said on Monday.

Gardiner’s frogs live in the rainforests of the Seychelles, a series of 115 small islands in the Indian Ocean, north of Madagascar.

Most frogs have eardrums on the outsides of their heads. The eardrums vibrate when incoming sound waves hit, sending the vibrations to the inner ear, then the brain. But not the wee Gardiner’s frogs, which measure about a centimetre long or the size of a thumbtack.

Researchers thought that the creatures might be deaf, until they tested them by playing pre-recorded sounds of other frogs croaking. They found that male Gardiner’s frogs croaked back, as if in conversation, proving they could hear.

Advanced X-ray images showed that neither the lungs or the muscles of the frogs were helping transmit sound to their inner ears.

Instead, scientists realised that the frog’s mouth is what acts as an amplifier for the sound frequencies the frog emits.

The system is boosted by very small amount of thin tissue between the mouth and inner ear. – Nampa-AFP

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