The Lungs of Female Frogs Tune Out Unwanted Males

They work like noise-cancelling headphones.
Loukia Papadopoulos

It has often been said that nature works in mysterious ways, and the more we find out about it the more we are impressed. Recently, scientists discovered that female frogs can use their lungs like noise-canceling headphones to silence the many unwanted male mating calls they are subjected to.

"In essence, the lungs cancel the eardrum's response to noise, particularly some of the noise encountered in a cacophonous breeding 'chorus,' where the males of multiple other species also call simultaneously," said lead author of the new research Norman Lee of St. Olaf College in Minnesota.

This practice is called "spectral contrast enhancement" and it makes the frequencies in the spectrum of a male's call stand out relative to noise at adjacent frequencies.

"This is analogous to signal-processing algorithms for spectral contrast enhancement implemented in some hearing aids and cochlear implants," added senior author Mark Bee of the University of Minnesota-Twin Cities.

"In humans, these algorithms are designed to amplify or 'boost' the frequencies present in speech sounds, attenuate or 'filter out' frequencies present between those in speech sounds, or both. In frogs, the lungs appear to attenuate frequencies occurring between those present in male mating calls. We believe the physical mechanism by which this occurs is similar in principle to how noise-canceling headphones work."

What's especially cool about this work is that it used publicly available data from a citizen science project called the North American Amphibian Monitoring Program. It was the researchers' analysis of this data that led them to conclude that the green treefrog's inflated lungs would make it harder to hear the calls of other species while leaving their ability to hear the calls of their own species intact.

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