FROG CALL INTENSITIES AND SOUND-PROPAGATION IN THE SOUTH-AMERICAN TEMPERATE FOREST REGION

Sound pressure levels and the spectral structure of the advertisement calls of five species of frogs from the South American temperate austr al forest were analyzed. Males of Eupsophus emiliopugini, Batrachyla a ntartandica and B. leptopus call from the ground in bogs, while males of Hylorina sylvatica and Pleurodema thaul call from the water surface in marshes. Calling males of the species from bogs and marshes spaced at average distances that were shorter and longer than 2 m, respectiv ely. The properties of these habitats for sound propagation were evalu ated by broadcasting pure tones, broadband noise and tape-recorded adv ertisement calls of the three species from bogs and of H. sylvatica. E xcess attenuation and spectral degradation were higher for calls broad cast in bogs than in the marsh. The calls of B. antartandica and B. le ptopus, with dominant frequencies of about 2 kHz, were more affected t han those of E. emiliopugini and H. sylvatica, with dominant frequenci es below 1.5 kHz. These results show the lack of an optimal relationsh ip between properties of habitats for sound transmission and the spect ral structure of these anuran calls. Body size imposes an important co nstraint on call spectra and propagation, which frogs counteract by di stribution patterns and auditory capabilities.