Data from: Rival assessment among northern elephant seals: evidence of associative learning during male-male contests

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.

处于竞争状态的雄性所释放的特化信号，通常能够传递与其战斗能力相关的诚实信息。学界普遍认为，信号接收者会借助此类信号直接评估自身的竞争对手。本研究针对冲突代价极高的繁殖系统，揭示了雄性所采用的一种另类交流策略。我们对繁殖期北象海豹（Mirounga angustirostris）雄性的声学展示行为进行了评估，结果发现：通过与信号发出者的过往互动所获得的社会认知，足以维持结构化的群体支配关系。借助声学分析以及天然、修饰化信号的回放实验，我们证实雄性个体并不会依赖编码有体型或支配地位信息的信号，而是通过学习识别竞争对手所产生的个体声学特征标识。此外，我们还发现，雄性对竞争者鸣声的行为反应会随其在社会等级中的相对位置发生调节：最高等级的阿尔法（alpha）雄性会针对所有对手守卫其配偶群，而中等级别的贝塔（beta）雄性则会根据过往竞争互动的结果，对熟悉的挑战者做出差异化响应。本研究结果表明，仅依靠对竞争对手的社会认知，即可在大型空间动态社会群体中调控竞争雄性间的支配关系；同时也阐明，在解析动物信号的生物学意义时，结合描述性与实验性研究方法的重要性。