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）’指出，复杂的社会结构是驱动动物通讯系统多样性的关键因素。抹香鲸具有层级化的社会结构，其最大的社交联结单元——发声宗族——在大洋盆地尺度上，以经文化传承的声学信号方言作为标识，这类信号被称为‘CodA（codas）’。本研究基于6年间采集自9个加勒比海社交单元的观测数据，分析了个体抹香鲸以及抹香鲸社会的基本构成单元——社交群体——的CodA曲目库变异特征。研究通过照片识别与声学尺度测量技术将CodA归属至对应个体，并同时采用连续型与分类型两种方法计算曲目库间的相似度。本研究共识别出21种CodA类型，其中两种（‘1+1+3’与‘5R1’）占总记录CodA的65%，在所有社交单元中均有分布，且至少30年来始终主导该种群的曲目库。个体间在‘5R1’的发声方式上存在显著差异，但‘1+1+3’的发声方式则无明显个体差别。各社交单元会使用独特的4次喀哒CodA类型，这一特征使得不同单元的曲目库具备专属辨识度。本研究结果在海洋物种中验证了社会复杂性假说：不同CodA类型的变异模式存在分化，暗示其功能各异，这或许代表了针对多层级社会结构下身份标识信号的选择压力。