A multilevel society of herring-eating killer whales indicates adaptation to prey characteristics

Non-social factors can influence animal social structure. In killer whales (Orcinus orca), fish- versus mammal-eating ecological differences are regarded as key ecological drivers of their multilevel society, including group size, but the potential importance of specific target prey remains unclear. Here, we investigate the social structure of herring-eating killer whales in Iceland and compare it to the described social structures of primarily salmon- and seal-eating populations in the Northeast Pacific, which form stable coherent basic units nested within a hierarchical multilevel society. Using 29023 photographs collected over 6 years, we examined the association patterns of 198 individuals combining clustering, social network structure, and temporal patterns of association analysis. The Icelandic population had largely weak but non-random associations, which were not completely assorted by known ranging patterns. A fission–fusion dynamic of constant and temporary associations was ob...

非社会因素可影响动物的社会结构。在虎鲸（Orcinus orca）中，以鱼类为食与以哺乳类为食的生态差异被认为是其多层级社会（multilevel society，包括群体规模）的关键生态驱动因素，但特定目标猎物的潜在重要性仍不明确。本研究针对冰岛海域以鲱鱼为食的虎鲸种群的社会结构展开调查，并将其与东北太平洋主要以鲑鱼和海豹为食的虎鲸种群已被描述的社会结构进行对比——后者形成了嵌套于层级式多层级社会中的稳定连贯基本单元。本研究依托6年间收集的29023张照片，结合聚类分析、社会网络结构分析以及关联时序分析方法，对198头个体的关联模式进行了考察。冰岛虎鲸种群的关联整体较弱但并非随机，且未完全按照已知的活动范围模式进行分组。持续关联与临时关联并存的裂变-融合动态（fission-fusion dynamic）已被观测到……