Lungs contribute to solving the frog's cocktail party problem by enhancing the spectral contrast of conspecific vocal signals

Noise impairs signal perception and is a major source of selection on animal communication. Identifying adaptations that enable receivers to cope with noise is critical to discovering how animal sensory and communication systems evolve. We integrated biophysical and bioacoustic measurements with physiological modeling to demonstrate that the lungs of frogs serve a heretofore unknown noise-control function in vocal communication. Lung resonance enhances the signal-to-noise ratio for communication by selectively reducing the tympanums sensitivity at critical frequencies where the tuning of two inner ear organs overlaps. Social network analysis of citizen-science data on frog calling behavior indicates the calls of other frog species in multi-species choruses are a prominent source of environmental noise attenuated by the lungs. These data reveal that an ancient adaptation for detecting sound via the lungs has been evolutionarily co-opted to create spectral contrast enhancement that contributes to solving a multi-species cocktail party problem.