Frequency modulated calls and species recognition in a neotropical frog

Summary The neotropical frogPhysalaemus pustulosus (Leptodactylidae) has a complex advertisement call and different call components perform different functions. The whine is a necessary and sufficient stimulus for species recognition. The chuck provides information about male body size that is used by females in mate choice (Ryan 1980, 1983), but the chuck must be combined with the species-identifying whine to elicit maximum behavioral responses from males and females. One of the important features of the whine in eliciting behavioral responses from both sexes is the direction of frequency modulation. This suggests that current models of species recognition in anurans based on a frequency filtering mechanism of the peripheral auditory system and selective responses to combinations of frequencies in the central nervous system are not sufficient to explain species recognition inP. pustulosus. Recent neurophysiological studies of the anuran torus semicircularis are discussed in terms of a mechanism for decoding frequency sweeps.