What’s so great about ‘chuck’?

From Burlington, Vt., at a meeting of the Animal Behavior Society

A little “chuck” sound that a kind of male frog can add to his call proves attractive to friends and foes alike. Now, researchers suggest an explanation for the sound’s wide appeal.

Small, dark túngara frogs, found in Mexico and northern South America, have become a classic animal for studies of communication. Males gather in pools and call, and females follow the sounds to find mates.

Unfortunately for the male frogs, their calls also reveal their locations to predators. The frog-eating bats Trachops cirrhosus swoop out of the night sky and grab calling males. Mosquitolike flies in the genus Corethrella will land on the back of a vocalizing frog, stroll to his nose, and take a meal from blood vessels in his nostrils.

Earlier work had established that bats, as well as female frogs, prefer a whining call followed by some chuck noises instead of a plain whine. It now turns out that flies also prefer the whine-chucks, says Ximena Bernal of the University of Texas at Austin.

Coincidence? Maybe not, says Bernal. She and her colleagues have been investigating whether chucks might indicate something about males that all three groups would benefit from knowing.

To see whether frequent chuckers might be high-quality males, for both mating and eating, the researchers measured frogs and recorded their calls. They found no correlation between frog physique and tendency to chuck.

Bernal and her colleagues found, however, that frogs are more likely to chuck as males crowd together. Detecting the presence of a bigger cluster of possible mates or meals could benefit all the searchers, the researchers suggest.

To hear an audio file of the plain whining call, click here.

To hear an audio file of the whining call followed by three chuck noises, click here.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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