Gardiner’s frog shouldn’t be able to hear. This dime-sized amphibian doesn’t have the right equipment for it.

In your head, sound waves pass through the flappy bits of your ear and vibrate a taut membrane—the eardrum. On the other side, three tiny bones transfer these faint air-borne vibrations into the fluid-filled inner ear, amplifying them along the way. In the inner ear, little hairs detect the vibrations and convert them into electrical signals that travel to your brain. This is how you hear, and it all depends upon the eardrum and the three bones within the so-called middle ear. Without these structures, 99.9 percent of the energy of incoming sound waves would be lost.

Gardiner’s frog doesn’t have a middle ear or