The structure of stereotyped calls reflects kinship and social affiliation in resident killer whales (Orcinus orca)
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A few species of mammals produce group-specific vocalisations that are passed on by learning, but the function of learned vocal variation remains poorly understood. Resident killer whales live in stable matrilineal groups with repertoires of seven to 17 stereotyped call types. Some types are shared among matrilines, but their structure typically shows matriline-specific differences. Our objective was to analyse calls of nine killer whale matrilines in British Columbia to test whether call similarity primarily reflects social or genetic relationships. Recordings were made in 1985–1995 in the presence of focal matrilines that were either alone or with groups with non-overlapping repertoires. We used neural network discrimination performance to measure the similarity of call types produced by different matrilines and determined matriline association rates from 757 encounters with one or more focal matrilines. Relatedness was measured by comparing variation at 11 microsatellite loci for the oldest female in each group. Call similarity was positively correlated with association rates for two of the three call types analysed. Similarity of the N4 call type was also correlated with matriarch relatedness. No relationship between relatedness and association frequency was detected. These results show that call structure reflects relatedness and social affiliation, but not because related groups spend more time together. Instead, call structure appears to play a role in kin recognition and shapes the association behaviour of killer whale groups. Our results therefore support the hypothesis that increasing social complexity plays a role in the evolution of learned vocalisations in some mammalian species.
KeywordsVocal learning Gene-culture coevolution Social network Kin recognition
We thank David E. Bain, David A. Briggs, Graeme M. Ellis, Alexandra Morton, Helena Symonds, Frank Thomsen and Stephen Wischniowski for contributing additional recordings for analysis. Helena Symonds and Nicola Rehn provided valuable comments on the manuscript. VBD was supported by a DAAD-Doktorandenstipendium aus Mitteln des 3. Hochschulsonderprogramms and a Marie-Curie Intra-European Fellowship.
- Bartlett P, Slater PJB (1999) The effect of new recruits on the flock specific call of budgerigars (Melopsittacus undulatus). Ethol Ecol Evol 11:139–147Google Scholar
- Bigg MA, Olesiuk PF, Ellis GM, Ford JKB, Balcomb KC (1990) Social organization and genealogy of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. Rep Int Whaling Comm Spec Issue 12:383–405Google Scholar
- Ford JKB (1987) A catalogue of underwater calls produced by killer whales (Orcinus orca) in British Columbia. Canadian Department of Fisheries and Oceans, Nanaimo, p 161Google Scholar
- Ford JKB, Ellis GM, Balcomb KC (2000) Killer whales—the natural history and genealogy of Orcinus orca in British Columbia and Washington State. University of British Columbia Press, VancouverGoogle Scholar
- Zar JC (1996) Biostatistical analysis. Prentice Hall, Upper Saddle RiverGoogle Scholar