Taxonomy

The genus Orcinus is considered to be monospecific, with a single species: O. orca. A second species, O. rectipinna, the Pacific killer whale, has been suggested, but is nowadays not considered to be a valid species (Duffield, 1986). Also O. nanus and O. glacialis have been suggested for a dwarf form of killer whale in the Antarctic, but also these species are considered invalid (Matkin and Leatherwood (1986), Klinowska (1991)).

Appearance

Killer whales are robust animals. Males grow to 6.7-8.2 m (maximum 9.5 m) and weigh 3,600-5,400 kg). Females are smaller at 5.2-7.3 m and they weigh 1,400-3,600 kg) (Fad, 1996). The head has a characteristic bulbous melon. The flippers are highly mobile and rounded, looking like large paddles. In males, these flipper can measure 2x1.2 m. The most striking feature is the large dorsal fin. It is tall ( 1.8 m or more) and triangular in males and may even be curved slightly forward. In juveniles, the dorsal fin is smaller and falcate (sickle-shaped).

The coloration is basically black dorsally and white ventrally. There is a grey "saddle" just behind the dorsal fin, a white patch behind the eye and a white or greyish intrusion on the side above the genital region. There is a lot of variation on the color and shape of the saddle and this can potentially be used for identification of individuals (Matkin and Leatherwood, 1986).

Distribution

Killer whales are true cosmopolitans and can be found in virtually all oceans and major seas. Usually they are found within 800 km from the coast (Klinowska, 1991). They occur in groups of 1 to 70-100 animals. Most studies have been done on the resident population in British Columbia and on the North Atlantic population. In the Eastern North Atlantic they are seen along the coast and also pelagically. Occassionally there are strandings and/or sightings in the Baltic Sea, the North Sea and the Mediterranean (Hammond and Lockyer, 1988).

Social structure

Quite some work has been done on the social structure of killer whales, especially in the BC area. The population in this area consists of 2 communities. First some definitions:

• Community: individuals that share a common range and associate with one another
• Pod: a group of individuals within a community that travels together the majority of the time
• Subpod: a group of individuals that separates temporarily from a pod to travel separately
• Intra-pod group: a cohesive group of individuals within a subpod that always travels in close proximity

Communities contain 3-16 pods (mean 9.5); pods contain 1-3 subpods (mean 1.7); subpods contain 1-11 (mean 1.9) intra-pod groups and intra-pod groups contain 2-9 (mean 3.6) individuals. The membership at each group level is rather stable, except for deaths and births (Bigg et al, 1990). There is a clear lack of dispersal, which is rather unusual for mammals. This lack of dispersal may give rise to a wide range of local races.

Apart from the resident population, there is also a transient population in the BC area. There are many behavioral differences between transients and residents, including feeding habits (in this area, the transients are the only whales that also feed on marine mammals). There is no mixing between resident and transient groups (Morton, 1990).

Pods along the Norwegian coast consist of 7-15 animals. Some animals travel quite a distance. 2 animals belonging to a pod first identified near Møre were later seen in the Lofoten, 700 km to the north (Lyrholm, 1988). A number of pods of various sizes has been identified in the Icelandic waters (5-30 animals). Occassionally, aggregates of 60-80 whales are encountered (Sigurjónsson et al, 1988). So far there is no evidence for mixing of the Icelandic and Norwegian populations. Also the analysis of vocalizations showed little evidence for mixing of the groups. Calls from Icelandic and Norwegian killer whales were quite different (Moore et al, 1988).

Population dynamics and life history

Female killer whales become sexually mature at 4.6-4.9 m in length (age 8 years) and males at 5.8 m (age 15 years). Physical maturity is attained at 20-25 years. Maximum longevity is at least 35 years (data for the Norwegian population, from Christensen (1984)).

For the BC population, Olesiuk et al (1990) report the following data: The mean life expectancy for females is 50.2 years (translates to an Annual Survival Rate (ASR) of 0.98). Their first viable calf is born at an age of 14.9 years. The maximum longevity is 80-90 years. Most births occur between October and March. Neonate mortality is fairly high at 43%. Males have a mean life expectancy of 29.2 years (ASR=0.966). They become sexually mature at 15 years and physically mature at 21 years. The maximum longevity is about 50-60 years.

Small and DeMaster (1995) calculated the ASR for killer whales kept in oceanaria. They found an Annual Survival Rate of 0.938 (pooled data for males and females). The difference between this value and the one reported by Olesiuk et al (1990) is statistically significant.

Population status

The BC and Washington population consisted of 261 animals in 1987 (Bigg et al, 1990). This population increased in size at a rate of 2.62% per year (Olesiuk et al, 1990). The population around Antarctica (south of 60°S) has been estimated at 70,000 animals. About 6,600 (3,500-12,000) animals are estimated to live in the Icelandic and Faeroese waters (Klinowska, 1991).

Exploitation

Killer whales have been killed in whaling operations worldwide, but there is no fishery directed specifically at this species. In the North Atlantic, there have been 2,661 catches this century. Fisheries in South Africa took on average 10 whales per year. This fishery stopped in 1976. There has been a commercial hunt by the USSR fleet in Antarctic waters. 50-170 whales have been killed in Japanese coastal fisheries per year. Hoyt (1990) reports the following catches:

Killer whale fisheries statistics (after Hoyt, 1990)

Country	Period	Number killed
Norway	1938-1981	2,452
U.S.S.R.	1935-1980	2,089
Japan	1946-1981	1,534

The killer whale has become a popular species for display in oceanaria. The first animal was captured for display in 1961. After that a number has been captured from Washington and British Columbia, until 1977. From 1974 to 1989 there has been a capture operation based on Iceland. There have also been a number of live captures conducted in Japan, from 1972. The most recent capture took place in Taiji, Japan in February 1997.

Killer whale live captures (after Hoyt, 1992)

Region	Period	Captured	Died	Kept	Released/escaped
California	1961	1	0	1	0
Washington	1962-1977	223-255	10	31	182-214
British Columbia	1962-1977	52	1	25	26
Iceland	1974-1989	64	0	55	9
Argentina	1985-1988	2(stranded)	0	2	0
Japan	1972-1997	27	0	18	9
Total		367-401	11	132	226-258

In September 1985, the first successful birth of a killer whale in captivity occurred in Sea World of Orlando. Since then there have been a number of successful killer whale births in captivity. Between September 1986 and September 1993, 11 out of 18 births were successful (Fad, 1996). Jerye Mooney (in a list compiled for the Animal Rights organisation PAWS in reaction to the live capture of 5 killer whales in Taiji, Japan, in February 1997) mentioned that of 54 known killer whales in oceanaria worldwide in February 1997, 17 (31%) were captive born.

Keeping cetaceans, especially killer whales in captivity has been a source of controversy for some time now. Some argue that oceanaria and marine mammal parks can and do play an important role in education and research (Watson (1995), Lockard (1986)) that can benifit whales and dolphins, while others diagree and argue that these animals should not be kept in oceanaria at all (Hoyt, 1992).

Feeding

The killer whale is an opportunistic feeder and that is reflected in the wide spectrum of prey species on its diet. It included a range of marine mammals, such as large baleen whales, including the blue whale and the humpback whale (Flórez-González, 1994), beaked whales, dolphins, porpoises, pinnipeds (seals, sea lions, elephant seals and walruses) and sea otters. There is also some evidence for cannibalism in killer whales. The diet also includes a large number of fish species, including sharks, herring, cod, capelin, halibut, mackerel, salmon and tuna. The killer whale also takes marine birds, especially penguins, and turtles as well as squid and octopus. See Hoyt (1990) for an extensive overview, with full references, of the killer whale diet.

Other

There have been numerous stories about friendly dolphins. There have also been a few friendly killer whales. In Twofold Bay, NSW, Australia, a group of killer whales participated in the whaling operation out of Eden. The most famous killer whale of theis group was "Old Tom" Old Tom got his name because he was believed to be between 50 and 90 years old when he died in 1930. Examination of the growth layers in his teeth revealed that he probably was about 35 years old when he died (Mitchell and Baker, 1980).

In 1990, a young killer whale surprised divers in Vestvold, Norway. It followed boats around and played with divers. It stayed around for a couple of weeks and then disappeared. The whale died in Randers, Denmark, in late summer, 1990, after spending some time in fresh water. This whale was first seen in a fjord in Stavern in spring 1989, then it was photographed from a ferry near Sunnmøre in autumn. And in April 1990 it showed up in Vestvold. An autopsy revealed that this whale was a 4-year old male, about 4 m long and weighing 800 kg (Anonymous, 1991).

References

Anonymous (1991)

Den utrolige spekkhoggeren. Dykkebladet Marmennell 1991-4:4-10

Bigg, M.A., Olesiuk, P.F., Ellis, G.M., Ford, J.K.B. and Balcomb III, K.C. (1990)

Social organization and genealogy of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. In: P.S. Hammond, S.A. Mizroch and G.P. Donovan (eds.): Individual recognition of cetaceans: Use of photo-identification and other techniques to estimate population parameters, pp. 383-403 (SC/A88/ID39). Rep. Int. Whal. Commn (Special Issue 12).

Christensen, I. (1984)

Growth and reproduction of killer whales, Orcinus orca, in Norwegian coastal waters. In: W.F. Perrin, R.L. Brownell Jr. and D.P. DeMaster (eds.): Reproduction in whales, dolphins and porpoises, pp. 253-258 Rep. Int. Whal. Commn (Special Issue 6).

Duffield, D. (1986)

Orcinus orca: Taxonomy, evolution, cytogenetics and population structure. in: B.C. Kirkevold and J.S. Lockard (eds.): Behavioral biology of killer whales, pp. 19-33 Alan R. Liss, Inc. New York

Fad, O. (1996)

The killer whale (Orcinus orca). Soundings 21(2):18-21, 26-32

Flórez-González, L., Capella, J.J. and Rosenbaum, H.C. (1994)

Attack of killer whales (Orcinus orca) on humpback whales (Megaptera novaeangliae) on a South American Pacific breeding ground. Marine Mammal Science 10(2): 218-222

Hammond, P.S. and Lockyer, Chr. (1988)

Distribution of killer whales in the eastern North Atlantic in: J. Sigurjónsson and S. Leatherwood: North Atlantic killer whales. pp.: 24-41 Rit Fiskideildar, Vol. XI. Hafrannsóknastofnunin, Reykjavík, Iceland.

Hoyt, E. (1990)

Orca - The whale called killer (New Edition). Robert Hale, London.

Hoyt, E. (1992)

The performing orca - Why the show must stop. Whale and Dolphin Conservation Society.

Klinowska, M. (1991)

Dolphins, Porpoises and Whales of the World. The IUCN Red Data Book. IUCN, Gland, Switzerland.

Lockard, J.S. (1986)

Research status of Orcinus orca: what is not known about its behavioral biology. in: B.C. Kirkevold and J.S. Lockard (eds.): Behavioral biology of killer whales, pp. 407-442 Alan R. Liss, Inc. New York

Lyrholm, T. (1988)

Photoidentification of individual killer whales, Orcinus orca, off the coast of Norway, 1983-1986 in: J. Sigurjónsson and S. Leatherwood: North Atlantic killer whales. pp.: 89-94 Rit Fiskideildar, Vol. XI. Hafrannsóknastofnunin, Reykjavík, Iceland.

Matkin, C.O. and Leatherwood, S. (1986)

General biology of the killer whale, Orcinus orca: A synopsis of knowledge in: B.C. Kirkevold and J.S. Lockard (eds.): Behavioral biology of killer whales, pp. 35-68 Alan R. Liss, Inc. New York

Mitchell, E. and Baker, A.N. (1980)

Age of reputedly old killer whale, Orcinus orca, 'Old Tom' from Eden, Twofold Bay, Australia in: W.F. Perrin and A.C. Myrick Jr (eds.): Age determination of toothed whales and sirenians, pp. 143-154 Rep. Int. Whal. Commn (Special Issue 3)

Moore, S.E., Francine, J.K., Bowles, A.E. and Ford, J.K.B. (1988)

Analysis of calls of killer whales, Orcinus orca, from Iceland and Norway in: J. Sigurjónsson and S. Leatherwood: North Atlantic killer whales. pp.: 225-250 Rit Fiskideildar, Vol. XI. Hafrannsóknastofnunin, Reykjavík, Iceland.

Morton, A.B. (1990)

A quantitative comparison of the behaviour of resident and transient forms of the killer whale off the Central British Columbia Coast. In: P.S. Hammond, S.A. Mizroch and G.P. Donovan (eds.): Individual recognition of cetaceans: Use of photo-identification and other techniques to estimate population parameters, pp. 245-248 (SC/A88/P17). Rep. Int. Whal. Commn (Special Issue 12).

Olesiuk, P.F., Bigg, M.A. and Ellis, G.M. (1990)

Life history and population dynamics of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. In: P.S. Hammond, S.A. Mizroch and G.P. Donovan (eds.): Individual recognition of cetaceans: Use of photo-identification and other techniques to estimate population parameters, pp. 209-243 (SC/A88/ID3). Rep. Int. Whal. Commn (Special Issue 12).

Sigurjónsson, J., Lyrholm, T., Leatherwood, S., Jónsson, E. and Víkingsson, G. (1988)

Photoidentification of killer whales, Orcinus orca, off Iceland, 1981 through 1986 in: J. Sigurjónsson and S. Leatherwood: North Atlantic killer whales. pp.: 99-114 Rit Fiskideildar, Vol. XI. Hafrannsóknastofnunin, Reykjavík, Iceland.

Small, R.J. and DeMaster, D.P. (1995)

Survival of five species of captive marine mammals. Marine Mammal Science 11(2): 209-226

Watson, P. (1995)

The cult of animal celebrity. Animal People #5 (June 1995): 6