Frog Hears With Its Mouth

The Gardiner’s Seychelles frog is the smallest frog ever found, at only 11 millimeters in length.  This frog doesn't have a middle ear, so scientists assumed it was deaf. Or were they? An experiment in which frogs sounds elicited a response indicated they could hear! But How?

So the scientists refocused their experiments on the frogs’ heads. By making various 3-D simulations of how sound travels through the frogs’ heads, the scientists found that the bones in their mouths act as an amplifier for sound waves.

Further x-rays showed that sound travels from the mouth to the inner ear, thanks to an evolutionary adaptation: The frogs have thinner and fewer tissue layers between the mouth and inner ear.

In essence, these frogs' mouth bones act as the equivalent of the hammer, anvil, and stirrup bones in humans. Read more about the experiments at NatGeo News.