Recognition of spectral patterns in the green treefrog: neurobiology and evolution

The natural communication behavior of frogs has provided a framework for studying both the mechanisms and evolution of sound pattern recognition. In the green treefrog behavioral studies using synthetic stimuli have identified the pertinent acoustic properties of its complex but stereotyped vocal signals. There are two optimal frequency bands: the most effective signals have about the same amount of energy in the two bands. Neurophysiological studies revealed biases for these two frequency bands at the level of the peripheral auditory system. Furthermore, the neural response properties in an auditory thalamic area are especially well correlated with selective phonotaxis based on the appropriate combination of low- and high-frequency sound energy. Comparing the optimal frequency bands in terms of female preferences with the range of frequencies produced by males in natural populations suggests that intraspecific mate choice based on call frequency alone is unlikely.