Effect of natural and synthetic noise on evoked vocal responses in a frog of the temperate austral forest

Animals using sound communication have developed different strategies to overcome noise interference, but studies have rarely examined animals behaving in their natural environments. Males of the leptodactylid frog Eupsophus calcaratus exposed to natural noises of wind, rain, creek and sea surf and to a band-pass noise encompassing the main spectral components of the conspecific advertisement call increased their call rate in the presence of noises of moderate level, and this effect was particularly strong for the band-pass noise. Frogs exposed to band-pass noise of different intensities increased their call rate in response to exposures of 66-78 dB RMS sound pressure level. Call duration followed similar trends, but the effects of noise exposure on this measure of evoked vocal response were not as strong as those on call rate. The vocal responsiveness of males of this species in the presence of noise denotes adaptations to cope with high interference, in spite of the relatively simple acoustic environment of the austral temperate forest. (c) 2005 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.