Susceptibility of evoked vocal responses to noise exposure in a frog of the temperate austral forest

Animals that communicate by means of acoustic signals show diverse strategies in the presence of noise interference. Penna et al. (2005, Animal Behaviour, 70, 639–651) found that the leptodactylid frog Eupsophus calcaratus from the temperate austral forest increases its vocal output in the presence of natural noises and a band-pass noise overlapping the main spectral components of its advertisement call. We subjected the sympatric species E. emiliopugini to similar experimental conditions to assess its response to noise exposure. Male E. emiliopugini showed no increase in vocal activity in the presence of moderate noise levels (67 dB RMS SPL, fast weighting) and decreased their vocal output in the presence of band-pass noise of increasing intensity (49–85 dB RMS SPL, fast weighting). However, E. emiliopugini, like E. calcaratus, increased the amplitude of their vocal responses in these circumstances. The vocal responses of males of E. emiliopugini under noise exposure and their contrast with the congeneric species unveil different strategies in confronting interference, whose origins and adaptive significance warrant further study.