Patterns of vocal interactions in a bullfrog (Rana catesbeiana) chorus: Preferential responding to far neighbors

In chorusing species, males seem to be spaced non-randomly, and their vocal interactions may be governed by particular behavioral rules. We monitored patterns of vocal interactions in a natural bullfrog (Rana catesbeiana) cho rus to determine the probability with which calls of individual frogs would follow each other's in dyadic sequences. Expected probabilities of respons es in a dyad were calculated based upon the joint probabilities of calling (relative calling rates) of the individual frogs; observed probabilities of response reflected the actual number of following responses in each dyad. Results of statistical tests comparing observed and expected probabilities of responding revealed that, when dyads were closely spaced, observed proba bilities of a following response were significantly less than the expected probabilities. Conversely, when dyads were composed of more distant males, observed probabilities of responding were significantly greater than expect ed. Observed probabilities of response were correlated with inter-male dist ances; males called more frequently than expected following calls of far ne ighbors, and less frequently than expected following calls of near neighbor s. These data suggest that males attend to both nearby and distant callers, and adjust the onset of their own vocalizations appropriately. Males may b e actively inhibited by calls of their near neighbors, and their calling ma y be actively elicited by the calls of their far neighbors.