Female Croakers - Noisy Frogs are not always the Men

Of all the members of the frog world, it has always been thought that the noisiest croakers are the males, who sing out to attract mates.

But now it seems that female frogs may occasionally do the same thing. Just before they are about to lay their eggs, female concave eared torrent frogs from the Huangshan Hot Springs in central China, call out with an ultrasonic peep to attract a male to come and fertilise them.

That's what a team of researchers led by Jun-Xian Shen from the Chinese Academy of Sciences in Beijing found out when they took some of these frogs into the laboratory.

They already suspected that the females had the ability to call, because when they dissected one, they discovered well developed vocal chords - something that most female frogs don't have.

And when they listened to the frogs with ultra-sonic detectors, they did indeed hear the females calling out when it was time to lay.

The team recorded these calls and played them back to males who responded immediately by hopping directly towards the source of the sound, sometimes in a single, well-aimed leap.

It is thought the females shriek at such a high pitch so they can be heard over the noisy babbling of the streams they live next to. And this puts these frogs among a small group of animals that communicate with ultra sound including bats, whales, dolphins and some insects.

And as well as telling us more about the wonderful goings on in the natural world, these findings may also have implications for studies of human hearing. By understanding more about how these frogs can so accurately detect and locate the source of particular calls may help scientists design more effective hearing aids for people.