The basic social unit of killer whales is the matrilineal unit, consisting of a female, her offsprings, and often a third generation. The dialect of each such matrilineal unit consists of a characteristic and unique set of calls. Most matrilineal units possess at least some calls which are unique to its members, but may share others with other, related, matrilineal units. However, such shared calls usually exist in several distinct versions, one for each matrilineal group which makes it.
Above is an example of such a shared call, the N4 call as made by 9 different matrilineal units of the Northern Resident Community inhabiting the coastal waters of British Columbia. On the left hand side you see spectrograms of the groups' versions of the N4 call. Click on the graphs to listen to the sounds.
The acoustic phylogeny on the right hand side was generated by training an artificial neural network to discriminate between 24 N4 calls of the different groups. Groups which link in the yellow have relatively similar calls, and the neural network could not tell them apart consistently, groups which link in the red are acoustically distinct, and gave good discrimination.
Spectrograms were made using Canary 1.2 and MATLAB.
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