Vocal Responses to Conspecific Call Variation in the Neotropical Frog Physalaemus enesefae

Abstract

Female Physalaemus enesefae prefer long calls, low and average dominant frequency calls, and calls repeated at short intercall intervals over short calls, high dominant frequency calls, and calls repeated at long intercall intervals. I tested the hypothesis that males modify their vocal behavior when faced with potential competitors in ways that make them more attractive to females and that the more attractive the competitor, the greater the modification. In playback experiments, I examined the responses of males to the same stimuli used to test female responses: long and short calls, calls with low or high dominant frequency, long and short intercall intervals, and average calls for all traits. Among the variables analyzed, only the intercall interval was modified in the presence of the experimental stimuli. Males significantly reduced the intercall interval (called at a faster rate) in response to all experimental calls, compared with that when vocalizing alone, except in response to short calls and to long intercall interval calls. Males did not respond differently to calls of average and above average attractiveness. There was no difference in the intercall interval in response to average and above average attractive stimuli. However, the intercall interval in response to unattractive calls was significantly longer than that in response to calls of average attractiveness. The results partially support the hypothesis: males modify their spontaneous calling behavior when faced with a competitor but do not show finely tuned graded responses in relation to the attractiveness of the competitor.