Calling strategies of male túngara frogs in response to dynamic playback

AbstractTúngara frogs produce calls of varying complexity that consist of a whine followed by 0–7 chucks. In previous studies using static playbacks, males increase chuck number in response to calls with 1 versus 0 chucks but not in response to 2 or 3 versus 1 chuck. Here we use dynamic playback in which an automated interaction program counts the number of chucks present in a call and responds according to a specified calling strategy which determines the number of chucks in the response call. Males added progressively more chucks in response to the models' strategies of de-escalate, match or escalate; there was a significant difference in the focal males' responses to the de-escalate versus the escalate strategies. Similarly, males changed their calling strategy in response to the de-escalate strategy of the model. There was no evidence of change in calling patterns, as estimated by entropy, among treatments and between experimental and field data. Males produced significantly more chucks in these experiments than in the field, but in both contexts the mean chuck number is low and never approaches the maximum observed in nature. These data suggest that males are cost-sensitive when it comes to adding chucks and that they are more influenced by vocal competitors that de-escalate rather than escalate number of chucks. These are patterns of calling not previously revealed in studies using static playbacks, and this study is another demonstration of the usefulness of dynamic playback in studies of animal communication.