title: Individual, unit and vocal clan level identity cues in sperm whale codas.
abstract: 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.
authors.affiliation: Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Jutland, Denmark; Department of Biology, Dalhousie University, Halifax, Canada B3H 4J1; Centre for Social Learning and Cognitive Evolution, and Sea Mammal Research Unit, School of Biology, University of St Andrews, St Andrews KY16 9TH, UK.
authors.forename: Shane
authors.initials: S
authors.lastname: Gero
authors.affiliation: Department of Biology , Dalhousie University , Halifax, Canada B3H 4J1.
authors.forename: Hal
authors.initials: H
authors.lastname: Whitehead
authors.affiliation: Centre for Social Learning and Cognitive Evolution, and Sea Mammal Research Unit , School of Biology, University of St Andrews , St Andrews KY16 9TH, UK.
authors.forename: Luke
authors.initials: L
authors.lastname: Rendell
keywords: cetaceans; communication; conformism; individuality; social complexity hypothesis; social structure