title: Rival assessment among northern elephant seals: evidence of associative learning during male-male contests.
abstract: Specialized signals emitted by competing males often convey honest information about fighting ability. It is generally believed that receivers use these signals to directly assess their opponents. Here, we demonstrate an alternative communication strategy used by males in a breeding system where the costs of conflict are extreme. We evaluated the acoustic displays of breeding male northern elephant seals (Mirounga angustirostris), and found that social knowledge gained through prior experience with signallers was sufficient to maintain structured dominance relationships. Using sound analysis and playback experiments with both natural and modified signals, we determined that males do not rely on encoded information about size or dominance status, but rather learn to recognize individual acoustic signatures produced by their rivals. Further, we show that behavioural responses to competitors' calls are modulated by relative position in the hierarchy: the highest ranking (alpha) males defend their harems from all opponents, whereas mid-ranking (beta) males respond differentially to familiar challengers based on the outcome of previous competitive interactions. Our findings demonstrate that social knowledge of rivals alone can regulate dominance relationships among competing males within large, spatially dynamic social groups, and illustrate the importance of combining descriptive and experimental methods when deciphering the biological relevance of animal signals.
authors.affiliation: Department of Ecology and Evolutionary Biology, and , University of California Santa Cruz , Santa Cruz, CA 95060, USA.
authors.forename: Caroline
authors.initials: C
authors.lastname: Casey
authors.affiliation: Equipe Communications Acoustiques, Neuro-PSI, CNRS UMR 9197 , Université Paris Sud , 91405 Orsay, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Charrier
authors.affiliation: Equipe Neuro-Ethologie Sensorielle, ENES/Neuro-PSI, CNRS UMR 9197 , Université de Lyon/Saint-Etienne , 23 rue Michelon, 42023 Saint-Etienne cedex 2, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Mathevon
authors.affiliation: Institute of Marine Sciences, Long Marine Laboratory , University of California Santa Cruz , Santa Cruz, CA 95060, USA.
authors.forename: Colleen
authors.initials: C
authors.lastname: Reichmuth
keywords: Mirounga; acoustic communication; individual recognition; male–male conflict; playback experiments; social network