| Abstract: | Summary The frog Heleioporus (Anura: Leptodactylidae) calls from a burrow. This paper examines the acoustic properties of the burrow by experimentally actuating plaster casts taken from five species: H. eyrei, H. psammophilus, H. albopunctatus, H. inornatus and H. barycragus. These findings are correlated with the properties of both natural calls of the frogs from the burrow and calls induced from the frog outside of the burrow. The morphology of the burrow enhances the principal frequency component of the call by resonance. Frogs call from a slight bulge beneath the burrow entrance. This calling site corresponds to the optimum position for generating a sound pressure maximum within the burrow. This was determined experimentally in an artificially constructed burrow with a complex internal sound source. In addition to optimizing the acoustic properties of the burrow the frog, in this position, has an open visual field from the burrow entrance. We conclude that the burrow system may compensate for the lack of a vocal sac in these frogs. |
