Vocal plasticity at different time spans during exposures to biotic and abiotic natural sounds in an austral temperate forest frog.

Several instances of short-term plasticity of reproductive behaviors are known to modulate interactions among competing individuals. Habituation and sensitization processes result in decrements and increments, respectively, of agonistic behaviors in breeding areas. The occurrence of such phenomena in the long term have been reported to a quite restricted extent. Frogs communicating acoustically experience auditory activation during days of exposure to conspecific signals, and thus we looked for vocal activation over such time span in male frogs Batrachyla taeniata. A total of 72 frogs were exposed during 8 or 10 days to 5 h of natural chorus sound, rain sound or left in silence, and subjected to stimulation with synthetic conspecific calls before and after such treatments. Results showed no significant variation of vocal activity between pre- and post-exposure days, indicating that no long-term plasticity phenomena occurred. However, within each day of exposure, an initial increment followed by a decrement in call rate was observed, pointing to processes of short-term sensitization and habituation or fatigue, respectively, but potential effects of photoperiod and energy depletion also need to be assessed. The lack of long-term sensitization of vocal activity contrasts with the auditory system activation for such time span reported for other anurans. The mismatch between both phenomena could relate to constraints imposed by the high energy expenditure that characterizes anuran vocal activity.