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In anurans—the group of tailless amphibians to which frogs and toads belong—vocalization is all about sex. Males produce the majority of these sounds, most often to attract mates and defend territories. Many species have vocal sacs that amplify these so-called advertisement calls, which vary widely. “Every species has [its] own unique call,” says population geneticist Benjamin Pierce of Southwestern University in Georgetown, Texas. “Some are grunts, some are trills, some are peeping noises.”
A DIVERSITY OF CHORUSES: Dozens of frog species call for mates. Vocalizations range from low frequency grunts to broad-spectrum trills. (Call of Hyla versicolor, pictured above, is not shown.)Despite the differences in vocalizations among frogs and toads, the repetitive nature of the calls is seen across diverse species. “Many of them call at—more or less—a fixed rhythm,” says zoologist Mike Ryan of the University of Texas at Austin. And heard in groups, he adds, “a lot of them sound very musical.”
Frogs rarely call in isolation. Males typically broadcast amongst a gaggle of competitors, and across the population, vocalizations overlap and syncopate—the animals are said to be chorusing. “Listening to a chorus of frog calls, it definitely has rhythm—it builds, it dies down—and it certainly can be ‘music,’” says Carlos Davidson, a professor of environmental studies at San Francisco State University.
“There’s melody, harmony, and repetition in frog calls,” agrees Phil Bishop, who studies amphibian communication ...
