Data from: Individual, unit, and vocal clan level identity cues in sperm whale codas

The ‘social complexity hypothesis’ suggests that complex social structure is a driver of diversity in animal communication systems. Sperm whales have a hierarchically structured society in which the largest affiliative structures, the vocal clans, are marked on ocean-basin scales by culturally transmitted dialects of acoustic signals known as ‘codas’. We examined variation in coda repertoires among both individual whales and social units—the basic element of sperm whale society—using data from nine Caribbean social units across six years. Codas were assigned to individuals using photo-identification and acoustic size measurement, and we calculated similarity between repertoires using both continuous and categorical methods. We identified 21 coda types. Two of those (‘1+1+3’ and ‘5R1’) made up 65% of the codas recorded, were shared across all units and have dominated repertoires in this population for at least 30 years. Individuals appear to differ in the way they produce ‘5R1’ but not ‘1+1+3’ coda. Units use distinct 4-click coda types which contribute to making unit repertoires distinctive. Our results support the social complexity hypothesis in a marine species as different patterns of variation between coda types suggest divergent functions, perhaps representing selection for identity signals at several levels of social structure.

‘社会复杂性假说（social complexity hypothesis）’提出，复杂的社会结构是驱动动物通讯系统多样性的核心动因。抹香鲸（sperm whale）拥有层级化的社会结构，其中最大的亲和性社会单元——发声宗族（vocal clans）——以大洋盆地尺度上经文化传承的声学信号方言为标识，这类声学信号被称为‘codas（断音序列）’。我们借助横跨6年的9个加勒比海社会单元的观测数据，针对个体鲸鱼以及社会单元——抹香鲸社会的基本构成单元——的断音序列曲目差异展开了系统分析。研究中通过照片识别与声学参数测量将断音序列分配至对应个体，并分别采用连续型与分类型方法计算曲目间的相似性。我们共识别出21种断音序列类型。其中两类（‘1+1+3’与‘5R1’）占记录到的断音序列总数的65%，在所有社会单元中均有分布，且至少30年来始终为该种群的优势曲目。个体在产出‘5R1’断音序列的方式上存在显著差异，但在‘1+1+3’断音序列的产出模式上则无明显区别。各社会单元拥有独特的4次点击断音序列类型，这一特征使得不同单元的断音曲目具备辨识度。我们的研究结果为海洋物种中的社会复杂性假说提供了实证支撑：不同断音序列类型的变异模式存在分化，暗示其功能存在差异，这可能代表了针对不同层级社会结构下身份标识的选择压力。