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This is Sign- 60 Second Science.

I'm Jason Goldman. In the shadow of Wanshan Mountain in southeastern China lives a beige frog with black stripes.

The concave-eared torrent frog, or Oterana-Tormota, gets its name from its unusual hearing apparatus.

It has kind of ear canal-like structure, like humans, and like most mammals.

For most prospecies, the eardrums are located on the body surface, on the lateral part of the body surface.

But here the eardum is invisible because it is embedded deep inside the head to the skull.

Biologist Albert Feng from the University of Illinois

at Urbana-Champaign.

Back in 2006, Feng and colleagues, discovered that this unusual anatomy allows the frogs to hear

ultrasound, which includes frequencies greater than 20 kilo-hertz.

Biologists had always assumed that ability was restricted to some mammals because it was only known in bats, whales, dolphins, and some rodents. We can't hear in that range.

The streams that the frogs live in are quite noisy, but most of those sounds are low frequency.

By restricting their vocalizations to the higher frequencies, including ultrasound,

the frogs are better able to including ultrasound.

The frogs are better able to hear each other. The higher the frequency, the less the signal is distorted,

or at least masked by the ambient noise.

In many animals, females prefer mating with larger males, usually because that's a sign of

health and strength.

And bigger males tend to produce lower frequency vocalizations.

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