Narins and Arch have an idea about why the frogs, which live along a noisy stream, use both ultrasonic communication and calls that are audible to humans.
"Our hypothesis is that these frogs have shifted to use higher frequencies in their communication to avoid the interference of sound produced by rushing water in the lower-frequency range," Arch said. "However, high-frequency sounds do not transmit as far. By producing some lower-frequency calls, they can transmit calls over a greater distance, so they can communicate with frogs that are farther away. But by also producing some calls that are high-frequency all ultrasonic they may be able to communicate better over that background noise.
"Producing both types of calls might be a bet-hedging strategy to be heard," Arch said. "This is how males attract females, communicate with one another and establish territorial boundaries."
The research may have implications for improving human hearing aids and addressing hearing loss. Most hearing aids, Narins said, simply amplify sound, including unnecessary background noise. Better hearing aids that are directional, for example, could result from the research.
In 1998, Kraig Adler, a professor of neurobiology and behavior who had been Narins' professor at Cornell University, told Narins he should go to China to see "a frog with an ear canal like a human," Narins recalled.
Narins took the advice. Along with colleagues, including Albert Feng from the University of Illinois, Urbana-Champaign, he discovered a frog species that lives in rushing streams and waterfalls in east-central China called Odorrana tormota (formerly known as Amolops tormotus). Odorrana tormota, Narins found, could detect and
|Contact: Stuart Wolpert|
University of California - Los Angeles