Bee, M.A.*; Gerhardt, H.C.: Getting to Know You: Habituation as a Mechanism for Territorial Neighbor Recognition

Territorial animals commonly exhibit low levels of aggression toward familiar neighbors in their usual territories and high levels of aggression toward strangers and neighbors in novel locations. Vocal recognition of neighbors is well known in songbirds, and also has been demonstrated in bullfrogs, Rana catesbeiana. Habituation has been suggested as a learning mechanism for neighbor recognition. However, no study has tested the hypothesis that repeated exposures to a neighbor’s acoustic signals allow territorial animals to learn about individually distinct signal properties and the usual location of signal origin. We conducted 3 field playback experiments using a habituation/discrimination procedure to test the hypothesis that habituation functions as a mechanism of neighbor recognition in bullfrogs. Synthetic bullfrog calls were broadcast to territorial males during a habituation phase until aggressive responses declined. We then presented novel stimuli during a subsequent discrimination phase. In experiment 1, a change in fundamental frequency, an individually distinct call property, elicited renewed aggression. In experiment 2, a 180^o change in stimulus location elicited renewed aggression. In experiment 3, changes in fundamental frequency, location, or both frequency and location elicited renewed aggression. Responses were highest to changes in fundamental frequency, and these responses were independent of location; responses to changes in location alone were intermediate between responses to changes in frequency and controls. Our data indicate that repeated exposure to a neighbor’s call resulted in stimulus-specific and location-specific response decrements, suggesting that habituation could function as a mechanism for neighbor recognition in bullfrogs.