Characteristics of whistles from the acoustic repertoire of resident killer whales (Orcinus orca) off Vancouver Island, British Columbia

The acoustic repertoire of killer whales (Orcinus or-cn) consists of pulsed calls and tonal sounds, called whistles. Although previous studies gave in formation on whistle parameters, no study has presented a detailed quantita tive characterization of whistles from wild killer whales. Thus an interpre tation of possible functions of whistles in killer whale underwater communi cation has been impossible so far. In this study acoustic parameters of whi stles from groups of individually known killer whales were measured. Observ ations in the field indicate that whistles are close-range signals. The maj ority of whistles (90%) were tones with several harmonics with the main ene rgy concentrated in the fundamental. The remainder were tones with enhanced second or higher harmonics and tones without harmonics. Whistles had an av erage bandwidth of 4.5 kHz, an average dominant frequency of 8.3 kHz, and a n average duration of 1.8 s. The number of frequency modulations per whistl e ranged between 0 and 71. The study indicates that whistles in wild killer whales serve a different function than whistles of other delphinids. Their structure makes whistles of killer whales suitable to function as close-ra nge motivational sounds. (C) 2001 Acoustical Society of America.