Distinctions in sound patterns of calls by killer whales (Orcinus Orca) from analysis of computer sound features

Abstract

Calls of killer whales, Orcinus orca, were analyzed using computed sound features to classify sound patterns and identify call similarties. Calls were classified and separated according to the podfamily group within clans identified previously by John Ford (U. BC) in the Vancouver whale populations. Acoustic characteristics of the same call type from different individuals were extremely similar, so that discriminating these different sounds was the goal. The WHOI AcouStat program and associated database systems were used to define numerical statistics for each call, and then, these were compared to sort and classify the sounds. The results were in agreement with Ford's descriptions of the calls derived from visual inspection of sound spectrograms of calls. The classification analyses demonstrated that although specific shared calls from different killer whales were much alike, they could be sorted by the pod/subpod of the whales producing the calls. A typical analysis, for example, of the N4 call from Clan A (Vancouver, BC), classified 97% of the calls correctly according to the pod/family of the whales producing the calls. Remaining calls were variant, and likely a result of individual differences in call sounds. Similar classification analysis were tested on unsorted, unalyzed recordings from different populations of whales, and these too could be distinguished, with 98.5% correct separation of the calls.