A frog in Anhui Province in China warbles and flutes with so much versatility that researchers, upon first hearing it, couldn’t believe it was what it is.
Frog calls rarely show a lot of diversity, says Albert S. Feng of the University of Illinois at Urbana-Champaign. The Boophis frogs of Madagascar once wowed the world with 28 distinct types of calls–which is why Feng rates the recent discovery in China “extraordinary.”
He and his colleagues were getting frustrated one night waiting for a little Amolops tormotus frog to make some noise. Feng and another researcher took a break from their vigil to try to find the source of warblerlike trilling coming from a nearby tangle of underbrush. When they got there, they didn’t find a bird at all; they found a frog. “Upon a closer inspection,” says Feng, “we were in for a bigger surprise: The callers were the very frogs we wanted to study.” The team simply hadn’t recognized their varying calls.
These frogs make “countless vocalizations,” the researchers report in the August Naturwissenschaften. Analysis of 12 hours of tapes from 21 males found no two calls to be identical either between animals or within an individual’s repertoire.
Also, the recordings chronicle the first known ultrasonic noises from frogs.
The frogs’ vocal variety, including multiple upward and downward sweeps of notes, are reminiscent of sounds made by birds, whales, and primates, say the researchers.
As for physiological quirks, the frogs’ eardrums are unusually deep in their skulls. Also, Feng says, video analysis suggests that a double set of vocal sacs contributes to the animals’ virtuosity.
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