Killer Whale Calls

Killer whales, Orcinus orca, live in matrilineal (mother plus her offspring) social groups. In the summer these groups sometimes come together with up to seven other matrilineal groups to form a "pod". Unlike many other mammals, male offspring tend not to disperse; they remain with their mother. Female offspring ultimately have offspring of their own and eventually split from their maternal group to form their own group. Whales fitting this social pattern are termed "residents". Transient killer whales show less group affiliation tendencies, but their social behavior is not as well understood.

Killer whales make calls and echolocation clicks. Calls are repeated (pulsed) sounds in the 1 to 10 Khz range; between 7 and 17 calls can be recognized by scientists, depending on the matrilineal group under study. Scientists recognize calls by listening to them, or by examining a graphical representation of the physical characeristics of the call, called a sonograph. It is more difficult, experimentally, to determine exactly how many different calls the whales actually perceive, and this remains an area of active scientific investigation.

Calls may be stereotyped, so that a call is quite similar each time it is given and varies little among individuals who give it. Information in stereotyped calls can be interpreted based on genetically coded information in the receiver. Stereotyped calls fit the model for innate releasing mechanisms of classical ethology. Call stereotypy is particularly valuable when the communicatory context is critical, such as an alarm call.

Alternatively, calls may vary among invididuals or social groups. Call variation can encode information about age, sex, social group membership, or other aspects of social status. In order to take advantage of variable calls, animals must be able to perceive call differences, associate a behavioral context to the call, learn that association, and remember it for future use. Variable calls are particularly useful in more complex aspects of social interactions.

Miller and Bain (2000) statistically analyzed calls from killer whales. They found that calls were more similar within matrilineal groups than between groups, and that over time, groups became more distinctive in their calls. Thus killer whale calls contain information that can be used to identify social groups, and may play a function in maintaining kin groups over time.

Miller, P. J.O. and D. E. Bain. 2000. Within-pod variation in the sound production of a pod of killer whales, Orcinus orca. Anim. Behav. 60:617-628.

Ford, J. K. B. 1989. Acoustic behavior of resident killer whales (Orcinus orca) in coastal waters of British Columbia. Can. J. Zool. 67:727-745.

Ford, J. K. B. 1991. Vocal traditions among resident killer whales (Orcinus orca) in coastal waters of British Columbia. Can. J. Zool. 69:1454-1483.