Acoustic behaviour of resident killer whales (Orcinus orca) off Vancouver Island, British Columbia

Abstract

Recordings of underwater vocalizations and behavioural observations were collected from 16 photographically identified resident pods of killer whales (Orcinus orca) off Vancouver Island, British Columbia, during 1978–1983. Vocalizations recorded during 43 days spent with three representative pods were analyzed for each of five activity states: foraging, travelling, group-resting, socializing, and beach-rubbing. The whales produced three types of sounds that were assumed to be social signals: discrete calls, variable calls, and aberrant calls. Discrete calls dominated vocalization in most contexts. An increase in production of variable and aberrant calls was observed during socializing and beach-rubbing activities. Each resident pod had a group-specific repertoire of 7–17 discrete call types (mean = 10.7) that was consistent over a number of years. The relative use of different calls varied with activity, but no call type was correlated exclusively with any behaviour or circumstance that could be identified. Discrete calls probably function as intragroup contact signals to maintain pod cohesion and coordinate activities. Structural modulations of standard call formats and variations in frequencies of call use appear to carry information on the emotional state of vocalizing individuals. Group-specific repertoires of calls may increase the effectiveness and reliability of this contact system and function as indicators of pod affiliation.

High-frequency modulated signals of killer whales (Orcinus orca) in the North Pacific

“…Samarra et al (2010) reported two different types of killer whale HFM signals with the two call types exhibiting similar structure, but with higher and lower frequency content. If the two signal types recorded in SCB were produced by different individuals, HFM signals could be used to identify individual group members or maintain group cohesion as described for discrete calls (Ford, 1989). The higher frequency content and lack of consistent down-sweeps of signals recorded in the Atlantic by Samarra et al (2010) may be a consequence of the spatial separation and variable use of high frequency signals between the populations.…”

“…Killer whales (Orcinus orca) produce a variety of acoustic signals including echolocation clicks for foraging and pulsed calls and whistles for communicative purposes (Ford, 1989). Killer whale echolocation clicks and pulsed calls have distinct characteristics, which together allow for the discrimination to species level (Au et al, 2004;Barrett-Lennard, 1996).…”

“…Killer whale echolocation clicks and pulsed calls have distinct characteristics, which together allow for the discrimination to species level (Au et al, 2004;Barrett-Lennard, 1996). North Pacific killer whales are known to produce whistles from 1-18 kHz (Thomsen et al, 2001;Ford, 1989). Samarra et al (2010) recently reported on Norwegian and Icelandic killer whales that use a high-frequency whistle type with observed fundamental frequencies ranging from 16.9-74.7 kHz.…”

Orchestration : the movement and vocal behavior of free-ranging Norwegian killer whales (Orcinus orca)

“…Resident pods possess unique vocal repertoires of stereotyped pulsed calls with primary energy between 1 and 6 kHz (Ford, 1989). These calls contain both a high-frequency component (HFC between 2 and 12 kHz, Hoelzel & Osborne, 1986) beamed forward from the melon and a less directional low frequency component (LFC between 80 and 2400 Hz, Ford, 1987).…”

“…The relative energy of these two components may cue conspecifics into the orientation of the signaler (Miller, 2002). Discrete, stereotyped calls constitute the majority of vocalizations in most behavioral contexts (Ford, 1989). Hitherto, the individual call type has largely been regarded as an arbitrary and interchangeable unit without any specific behavioral significance.…”