Synchronous Vocal Response Mediated by the Amphibian Papilla in a Neotropical Treefrog: Behavioural Evidence

Acoustic playback experiments with treefrogs (Eleutherodactylus coqui Thomas) in their natural habitat reveal that males readily synchronize their vocalizations with synthetic calls containing frequencies equal to or lower than their own. Low-level artificial stimuli were used in order preferentially to stimulate auditory fibres originating in the amphibian papilla while avoiding excitation of basilar papillar or saccular fibres. Moreover, the synchronous vocal response persists unabated, even when the synthetic calls were simultaneously 'masked' with narrowand wide-band noise, which strongly excited a large fraction of the basilar papillar fibres. These behavioural findings support the hypothesis that the amphibian papilla alone mediates this critical vocal behaviour.