Neighbour–stranger discrimination by territorial male bullfrogs (Rana catesbeiana): II. Perceptual basis

Abstract

Territorial animals commonly display lower levels of aggression towards familiar neighbours in familiar locations than towards neighbours in unfamiliar locations and towards unfamiliar individuals. A combination of acoustic signals and spatial cues mediates this form of social recognition in a variety of animals, including the North American bullfrog,Ranacatesbeiana . In this study, we conducted two field playback experiments to investigate the perceptual basis of neighbour–stranger discrimination in bullfrogs. In a discrimination test following habituation training, a change of 10% in the fundamental frequency or 180° in the broadcast location of a synthetic bullfrog advertisement call elicited significant recovery of habituated aggressive responses. Hence, male bullfrogs can learn about an individually distinct property of acoustic signals and the signal's location of origin by repeatedly hearing the signal from a particular location. This study represents the first direct test of the hypothesis that territorial residents can learn about a specific property of a neighbour's acoustic signals and the location from which these are normally produced as a result of repeated exposures to the signal. We suggest that reduced aggression between territorial neighbours could be partially mediated by habituation to a neighbour's signals and location in bullfrogs.