Killer whales (Orcinus orca) are thought to learn their vocal dialect. Dispersal in the species is rare, but effects of shifts in social association on the dialect can be studied under controlled conditions. Individual call repertoires and social association were measured in three adult female killer whales and three males (two juveniles and an adult) during two periods, 2001–2003 and 2005–2006. Three distinct dialect repertoires were represented among the subjects. An adventitious experiment in social change resulted from the birth of a calf and the transfer of two non-focal subjects in 2004. Across the two periods, 1691 calls were collected, categorized and attributed to individuals. Repertoire overlap for each subject dyad was compared with an index of association. During 2005–2006, the two juvenile males increased association with the unrelated adult male. By the end of the period, both had begun producing novel calls and call features characteristic of his repertoire. However, there was little or no reciprocal change and the adult females did not acquire his calls. Repertoire overlap and association were significantly correlated in the first period. In the second, median association time and repertoire similarity increased, but the relationship was only marginally significant. The results provided evidence that juvenile male killer whales are capable of learning new call types, possibly stimulated by a change in social association. The pattern of learning was consistent with a selective convergence of male repertoires.
↵* Present address: National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115, USA.
A.E.B. was responsible for study design and oversight and statistical analysis. J.L.C. was responsible for data collection, reduction and analysis. A.G. supervised animal research and provided data on behavior. A.E.B. and J.L.C. prepared and edited the manuscript.
The authors declare no competing financial interests.
Funding for the study was provided by Hubbs-SeaWorld Research Institute (HSWRI) and the Hubbs-SeaWorld Society. J.L.C. received funding from the University of San Diego and the Hannon Foundation.
Supplementary material available online at http://jeb.biologists.org/lookup/suppl/doi:10.1242/jeb.094300/-/DC1
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