Environmental influences on anuran sound communication

Abstract

Studies of anuran vocal behavior in the South American temperate forest may represent the southernmost influence of Robert Capranicas comparative approach to sound communication. Vocalizations of leptodactylid frogs in this region exhibit patterns of propagation characteristic for different microhabitats. Calls containing frequencies above about 1 kHz experience higher attenuations in bogs as compared to marshes, irrespective of the species native environment. A similar lack of optimal relationships between signal structure and habitat properties for call propagation occurs in sound environments other than the temperate austral forest, as indicated by joint studies with colleagues from Cuba in Caribbean tropical forests and from Spain in European Mediterranean habitats. Anurans from southern Chile calling in bogs have peculiar acoustic adaptations: males call from burrows inside which the calls of neighboring cospecifics are amplified considerably. This effect potentially counteracts the constraints for signal propagation of sound-attenuating environments. The evidence presented indicates that anuran calls have not been subjected to environmental selection pressures, to the extent vocalizations of other vertebrates have. Dispersion of anurans is limited by availability of water sources, but males can choose locations favoring signal broadcast and reception in their relatively restricted breeding areas. [Work supported by FONDECYT Grant No. 1010569.]