Acoustic Behavior of Antarctic Killer Whales (Orcinus orca) Recorded Near the Ice Edge of McMurdo Sound, Antarctica

摘要

Underwater acoustic recordings of a group of seven to nine killer whales (Orcinus orca) were made opportunistically along a lead within the fast-ice in McMurdo Sound, Ross Sea, Antarctica in early December 1979. At the time of the recordings, the killer whale group was chasing Adelie penguins (Pygoscelis adeliae); however, no predation events were observed. A total of 87 min and 39 s were recorded and examined, with 506 sounds analyzed. The animals produced echolocation clicks, buzz sequences, pulsed signals, and whistles. Seven previously undocumented call types were described from these killer whales based on consistent aural and spectrographic analysis of signals. Acoustic measurements were made in the frequency and time domains using spectrographic and power spectrum analysis. This preliminary study is the first quantitative report on the acoustic features of underwater sounds produced by a specific group of killer whales in Antarctic waters. The acoustic characteristics are similar to sounds described from killer whale populations throughout the world, and the consistent repetition of call types suggests a pod-specific repertoire. Three different ecotypes of killer whales have been described in Antarctic waters based on their color pattern, habitat use, and prey preference. The group of animals recorded in this study is believed to be Type C killer whales based on photographs as well as behavioral observations at the surface. In order to compare vocal repertoires and acoustic behavior with analogous sympatric ecotypes from, for example, the Northeast Pacific, it will be necessary to analyze calls made from the other known Antarctic ecotypes. Acoustic analyses could very likely be a reliable diagnostic tool for identifying sympatric ecotypes in Antarctic waters.