Ultrasonic Frog Tunes Its Ears Like a Radio Dial

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The finding is detailed in this week's issue of the Proceedings of the National Academy of Sciences.

"This mechanism is truly unique in the animal kingdom," commented James Saunders, an auditory expert at the University of Pennsylvania.

Saunders pointed out that humans can also "selectively hear" different sounds. For instance, people can single out the sound of a bassoon over other instruments during an orchestra recital.

But selective auditory attendance in humans is mostly a trick of the mind. It involves neurons in the brain homing in on sounds coming from certain directions.

By contrast, the Chinese frogs have evolved the biological equivalent of earmuffs to block out all sounds of a certain frequency range.

Switching Channels

Study co-author Feng speculates that the frogs' tunable ears are an adaptation to their noisy home environments.

For example, shifting to high-frequency hearing could help the frogs pick out mating calls during a storm, when the low-pitched noises of plunking raindrops, booming thunder, and rushing water dominate.

"If you or I were in this situation, we would be trapped," Feng said.

"The background noise is coming from everywhere, so our kind of selective hearing wouldn't do us any good.

"The frogs just say, I'm not hearing this. I'm going to switch to another channel."

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