The experiment also raised the question of whether frogs might use ultrasonics for echolocation, the method bats and dolphins use to find their way around. "They usually respond by producing calls and approaching the speaker, presumably to ward of an intruder," Feng told LiveScience. One croaked 18 times in response to the test. The researchers set up a speaker that played both audible and ultrasonic torrent frog croaks and tested how eight males responded to the calls.įive of the males produced more croaks to both audible and ultrasonic calls than they'd normally belt out spontaneously. This assembly is similar in structure to the tweeter speakers in your stereo, and is prime for hearing ultrahigh-frequency sounds. It also allows for the ear bones that connect the drum to sound processing part of the ear to be shorter and lighter. Being recessed prevents the eardrums from tearing on twigs and brush. But torrent frogs have extremely thin eardrums recessed in their ears. Most frogs have thick eardrums close to the surface of their skin. The key to hearing the sounds is these frogs' special ear configuration. Torrent frogs, however, have been recorded chirping at 128 kHz-way above the 20 kHz at which most humans tap out. So torrent frogs evolved the ability to both produce and hear ultrasonic sounds, which most animals cannot pick up on.įor most amphibians, reptiles, and birds, the upper frequency limit for hearing sits around 12 kilohertz. It also broadcasts the frog's location to potential predators. Producing extra-loud calls is like trying to shout for long periods of time-it consumes a lot of energy and is difficult to maintain. The other is to shift frequency away from the background noise." "If the frogs want to communicate, they have two options," said Albert Feng of the University of Illinois at Urbana-Champaign.
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