Some territorial animals exhibit a form of social recognition, commonly termed the "dear enemy effect", in which territory residents display lower levels of aggression toward familiar neighbors compared to unfamiliar individuals who are non-territorial "floaters". Despite the widespread occurrence of territorial social systems and use of acoustic signals for communication in anuran amphibians, only two previous studies have demonstrated vocally mediated dear enemy behavior in a territorial frog. In this study, I conducted neighbor-stranger discrimination playback experiments in a third species of territorial frog, the strawberry dart-poison frog, Dendrobates pumilio (Anura, Dendrobatidae). In the first experiment (n=24), I broadcast the calls of a subject's nearest neighbor and the calls of an unfamiliar individual from the approximate midpoint between the subject's and the neighbor's territories. Although males responded to the stimuli, they did not exhibit differential responses to the calls of neighbors and strangers. In a second experiment (n=22), I broadcast the calls of a neighbor and a stranger to subjects through a speaker located in the approximate center of the neighbor's territory. Males also responded to the playback, although less intensely than in the first experiment, but no discrimination between the calls of neighbors and strangers was found. Thus, territorial males of the strawberry dart-poison frog appear not to discriminate behaviorally between the advertisement calls of neighbors and strangers. Several proximate and ultimate-level hypotheses for this lack of vocally mediated neighbor-stranger discrimination are discussed.
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Acknowledgements I thank John Christy, Luis Mao, Carlos Dixon, and Enrike Downer for logistical support in Panama, Carl Gerhardt for equipment, and Sarah Humfeld, Vince Marshall, Stephanie Palmer, and Sandra Blumenrath for comments on earlier versions of the manuscript. The author was supported by a Doctoral Dissertation Improvement Grant from the National Science Foundation and a Short-term Fellowship from the Smithsonian Tropical Research Institute. The research in this study was approved by the University of Missouri IACUC (protocol no. 3479) and the Republic de Panama Instituto Nacional de Recursos Naturales Renovable (permit no. 26-200) and complies with all of the laws of the United States of America and Panama.
- Dart-poison frog
- Dear enemy effect
- Dendrobates pumilio
- Neighbor recognition
- Territorial aggression