Complex call production in the tungara frog

摘要

Animals' sound-producing organs often act as an integrated whole - particular vocal structure are not directly associated with the creation of discrete syllables. But here we show that the 'chuck' of the 'whine-chuck' mating call of the tungara frog, Physalaemus pustulo-sus, is caused by a fibrous mass attached to the vocal folds; the chuck is eliminated by removal of this structure, although the frog still tries to produce the sound. Sexual selection affects the acoustic complexity of the frog's call, so evolution may have shaped this unusual vocalization, which is akin to the two-voiced song of songbirds.