Most female frogs don’t call; most lack or have only rudimentary vocal cords. A typical female selects a mate from a chorus of males and then –silently – signals her beau. But the female concave-eared torrent frog, Odorrana tormota, has a more direct method of declaring her interest:
She emits a high-pitched chirp that to the human ear sounds like that of a bird.
O. tormota lives in a noisy environment on the brushy edge of streams in the Huangshan Hot Springs, in central China, where waterfalls and rushing water provide a steady din. The frog has a recessed eardrum, said Albert Feng, a professor of molecular and integrative physiology at the University of Illinois and team leader on the new study.
In the world we know of only two species – the other one in southeast Asia – that have the concave ear,” Feng said. “The others all have eardrums on the body surface.”