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Orcinus orca

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA CETARTIODACTYLA DELPHINIDAE

Scientific Name: Orcinus orca
Species Authority: (Linnaeus, 1758)
Common Name(s):
English Killer Whale, Orca
French Orque, Epaulard
Spanish Espadarte, Espadarte, Orca
Synonym(s):
Orcinus glacialis (Berzin & Vladimirov, 1983)
Orcinus nanus Mikhalev et al., 1981
Taxonomic Notes: Killer Whales are presently considered to form a single cosmopolitan species, Orcinus orca (Rice 1998). Separate species status has been suggested for different morphological forms found in the southern Ocean (Mikhalev et al. 1981, Berzin and Vladimirov 1983, Pitman and Ensor 2003). Pitman et al. (2007) describe one of these as a dwarf form of Killer Whale. Killer Whales in the eastern North Pacific are known to consist of at least two and maybe three distinct forms, colloquially known as ‘resident’, ‘transient’ and ‘offshore’ Killer Whales (Ford 2002). Separate species status has also been suggested for at least two of these different forms, based on color pattern, diet, association patterns and morphological traits (Baird et al. 1992, Baird 1994). Genetic differences are found among these forms, with particularly marked differences between resident and transient forms (Stevens et al. 1989, Hoelzel and Dover 1991, Hoelzel et al. 1998, Barrett-Lennard 2000). The taxonomy of this genus is clearly in need of review, and it is likely that O. orca will be split into a number of different species or at least subspecies over the next few years (Reeves et al. 2004).

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2013
Date Assessed: 2008-07-01
Assessor(s): Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L.
Reviewer(s): Hammond, P.S. & Perrin, W.F.
Justification:
This taxonomic unit is treated as one species even though there is evidence that it may be a complex of two or more species. If it is so designated, the category of this taxon may change. If taxonomic designations change, then it is suspected that some new species may warrant listing under higher categories of risk. Because additional data should resolve this taxonomic uncertainty, the current species is listed as DD. The combination of potential declines driven by depletion of prey resources and the effects of pollutants is believed sufficient that a 30% global reduction over three generations (77 years; Taylor et al. 2007) cannot be ruled out for some “groups” that may be designated as species.
History:
2008 Data Deficient
1994 Insufficiently Known (Groombridge 1994)

Geographic Range [top]

Range Description: The killer whale is the most cosmopolitan of all cetaceans and may be the second-most widely-ranging mammal species on the planet, after humans (Rice 1998). Killer whales can be seen in virtually any marine region, from the equator to polar waters. Although they are generally more common in nearshore areas and in higher-productivity areas and/or higher latitudes, there appear to be no hard and fast restrictions of water temperature or depth on their range. The distribution extends to many enclosed or partially-enclosed seas, such as the Mediterranean Sea, Sea of Okhotsk, Gulf of California, Gulf of Mexico, Red Sea, and Persian Gulf. However, there are only extralimital records from the Baltic Sea and no records from the Black Sea.

The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states.
Countries:
Native:
Algeria; American Samoa (American Samoa); Antarctica; Antigua and Barbuda; Argentina; Aruba; Australia; Bahamas; Bangladesh; Barbados; Belize; Benin; Bermuda; Bonaire, Sint Eustatius and Saba (Saba, Sint Eustatius); Brazil; British Indian Ocean Territory; Brunei Darussalam; Cambodia; Cameroon; Canada (Newfoundland I); Cape Verde; Cayman Islands; Chile; China; Cocos (Keeling) Islands; Colombia; Comoros; Congo; Congo, The Democratic Republic of the; Cook Islands; Costa Rica; Côte d'Ivoire; Cuba; Curaçao; Denmark; Djibouti; Dominica; Dominican Republic; Ecuador (Galápagos); El Salvador; Equatorial Guinea; Falkland Islands (Malvinas); Faroe Islands; Fiji; France; French Guiana; French Polynesia; French Southern Territories (Kerguelen); Gabon; Gambia; Ghana; Gibraltar; Greenland; Grenada; Guadeloupe; Guam; Guatemala; Guinea; Guinea-Bissau; Guyana; Haiti; Heard Island and McDonald Islands; Honduras; Iceland; India; Indonesia; Iran, Islamic Republic of; Ireland; Israel; Italy; Jamaica; Japan; Kenya; Kiribati; Liberia; Madagascar; Malaysia; Maldives; Marshall Islands; Martinique; Mauritania; Mexico; Micronesia, Federated States of ; Monaco; Morocco; Mozambique; Myanmar; Namibia; Nauru; Netherlands; Netherlands Antilles (Bonaire); New Caledonia; New Zealand; Nicaragua; Nigeria; Niue; Northern Mariana Islands; Norway; Oman; Pakistan; Palau; Panama; Papua New Guinea; Peru; Philippines; Pitcairn; Portugal; Puerto Rico; Russian Federation; Saint Helena, Ascension and Tristan da Cunha; Saint Kitts and Nevis; Saint Lucia; Saint Martin (French part); Saint Pierre and Miquelon; Saint Vincent and the Grenadines; Samoa; Senegal; Sierra Leone; Singapore; Sint Maarten (Dutch part); Solomon Islands; Somalia; South Africa; South Georgia and the South Sandwich Islands; Spain; Sri Lanka; Suriname; Svalbard and Jan Mayen; Taiwan, Province of China; Tanzania, United Republic of; Thailand; Timor-Leste; Togo; Tonga; Trinidad and Tobago; Tunisia; United Arab Emirates; United Kingdom; United States (Aleutian Is., Hawaiian Is.); United States Minor Outlying Islands; Uruguay; Vanuatu; Venezuela, Bolivarian Republic of; Viet Nam; Virgin Islands, British; Virgin Islands, U.S.; Wallis and Futuna; Western Sahara; Yemen
Vagrant:
Germany
FAO Marine Fishing Areas:
Native:
Arctic Sea; Atlantic – eastern central; Atlantic – Antarctic; Atlantic – southeast; Atlantic – northwest; Atlantic – northeast; Atlantic – southwest; Atlantic – western central; Indian Ocean – Antarctic; Indian Ocean – eastern; Indian Ocean – western; Mediterranean and Black Sea; Pacific – northeast; Pacific – northwest; Pacific – southeast; Pacific – eastern central; Pacific – western central; Pacific – Antarctic; Pacific – southwest
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Although killer whales occur worldwide, densities increase by 1-2 orders of magnitude between the tropics and the highest-sampled latitudes in the Arctic and Antarctic (Forney and Wade 2006). Killer whales tend to be more common along continental margins; however, there is some variation in this general pattern that appears linked to ocean productivity. Killer whales appear to be less common in western boundary currents, such as the Gulf Stream or the Kuroshio than in more productive eastern boundary currents, such as the California Current. Known areas of locally higher density often coincide with greater oceanographic productivity (e.g. off Argentina).

Killer whale populations have been relatively well-studied in the North Pacific. In the eastern tropical Pacific, a line-transect survey resulted in an estimate of 8,500 (CV=37%) (Wade and Gerrodette 1993). A catalogue of 86 individuals exists for waters around the Baja Peninsula, Mexico (Guerrero-Ruiz et al. 1998). In waters of Hawaii, a line-transect survey estimated 430 (CV=72%) (Barlow 2003). The southern resident subpopulation that inhabits the inland waters of Washington and southern British Columbia recently numbered 90 whales; it is apparently depleted and considered to be endangered (Ford et al. 2000; K. Balcomb pers. comm., Krahn et al. 2004). The northern resident subpopulation of British Columbia recently numbered 216 (Ford et al. 2000; Angliss and Outlaw 2005). The west coast transient subpopulation catalogue included 314 individual whales (Ford and Ellis 1999; Angliss and Outlaw 2005). A photographic catalogue of offshore type killer whales identified 211 individuals from British Columbia to California (Ford et al. 2000; Black et al. 1997), but this is likely an underestimate of the subpopulation size. A line-transect survey extending out to 300nm offshore resulted in an estimate of 466 (CV=35%) in California and 898 (CV=35%) in Washington and Oregon (Barlow 2003); these estimates likely include whales from the aforementioned west coast transient, southern resident, northern resident, and offshore subpopulations. A line-transect survey from the Aleutian Islands to the Gulf of Alaska resulted in an estimate of abundance for transient killer whales of 251 (CV=51%) (Zerbini et al. 2006), while the AT1 transient subpopulation (which inhabits Prince William Sound and waters of the Seward Peninsula, Alaska) numbers only 11 animals (Matkin et al. 1999; Angliss and Outlaw 2005). A Gulf of Alaska resident killer whale catalogue includes 507 individuals (Matkin et al. 1999) while a line-transect survey from the Aleutian Islands to the Gulf of Alaska resulted in an estimate of 991 (CV=51%) (Zerbini et al. 2006). Line-transect surveys suggest there are at least hundreds of killer whales in the western North Pacific, including waters around Japan (Miyashita 1993). Preliminary studies suggest as many as 700-800 killer whales may be in Russian waters of the Pacific, but an abundance estimate has yet to be calculated (Miranova et al. 2002).

Line-transect surveys have resulted in estimates of abundance in several regions in the North Atlantic, including an estimate of 133 (CV=49%) in the northern Gulf of Mexico (Waring et al. 2006), 3,100 (CV=63%) in Norwegian waters (Øien 1990), and 6,618 (CV=32%) in Iceland and Faroes Islands waters (Gunnlaugsson and Sigurjónsson 1990; Sigurjónsson et al. 1989).

Several analyses of line-transect surveys have yielded abundance estimates for killer whales around Antarctica (Ohsumi 1981; Hammond 1984; Kasamatsu and Joyce 1995); however, some of the estimates have been considered biased by methodology and survey coverage (Branch and Butterworth 2001). More recent analyses that account for some of these biases resulted in an estimate of about 25,000 for waters south of 60ºS (Branch and Butterworth 2001); however, there are still uncertainties related to coverage of areas in the pack ice, so true abundance could be higher. Densities are known to vary locally within Antarctic waters, ranging from very abundant to uncommon (Secchi et al. 2002; Pitman and Ensor 2003), and it has been recognized that killer whale densities are higher closer to the ice edge, where the smaller-type killer whales can occur in large aggregations of tens to hundreds of animals (Berzin and Vladimirov 1983; Pitman and Ensor 2003). Photo-identification studies have found 25-30 whales around Marion Island (Keith et al. 2001). In other parts of the southern Hemisphere, an estimate of 119 (CV=20%) has been made in New Zealand waters (Visser 2000), and 30 have been identified off Argentina (Lopez and Lopez 1985; Iñíguez 2001).

Although the available data are far from complete, abundance estimates for the areas that have been sampled provide a minimum worldwide abundance estimate of about 50,000 killer whales. It is likely that the total abundance is higher, because estimates are not available for many high-latitude areas of the northern hemisphere and for large areas of the South Pacific, South Atlantic, and Indian Ocean. However, this population abundance refers to several forms of killer whales that may be recognized as different species or subspecies in the future (Reeves et al. 2004).
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: Killer whales may occur in virtually any marine or estuarine habitat but are most common in areas of high marine productivity, particularly at higher latitudes and near shore (Dahlheim and Heyning 1999; Forney and Wade 2006). Sightings range from the surf zone to the open sea. Movements can be extensive. For instance, some killer whales have been documented to have moved between Alaska and central California, a distance of more than 2000 km. In the Antarctic, they readily enter areas of floe ice in search of prey (Pitman and Ensor 2003). Killer whales in some areas congregate seasonally in coastal channels to forage and occasionally enter river mouths.

Killer whales are known to feed on a wide array of prey, including most marine mammal species (except river dolphins and manatees), seabirds, sea turtles, many species of fish (including sharks and rays) and cephalopods (Dahlheim and Heyning 1999; Ford and Ellis 1999; Ford 2002). They have a diversity of foraging tactics, including intentional beaching to gain access to seals onshore. They are known to use cooperative techniques to herd fish and to attack large prey (Dahlheim and Heyning 1999; Baird 2000).

Although a generalist as a species, at least some subpopulations specialize on particular types of prey (Bigg et al. 1990; Baird 2000). Studies in coastal waters of the eastern North Pacific, from California to Alaska, have described three distinct ecotypes of killer whales, referred to as residents, transients, and offshores. Although distinguished by ecological differences, there are also differences in coloration, external morphology, behavior and acoustics. The three ecotypes maintain social isolation from each other despite overlapping ranges. The northeastern Pacific residents are salmon specialists and have a strong preference for one species, the chinook salmon (Ford and Ellis 2006). Transients in coastal waters of the northeastern Pacific appear to focus their foraging on pinnipeds and small cetaceans and occasionally take baleen whales. Killer whales in coastal Norway specialize on herring (Simila et al. 1996) and in the Strait of Gibraltar on bluefin tuna (Cañadas and de Stephanis 2006). Some killer whales in New Zealand may forage selectively on rays and other elasmobranchs (Visser 1999). In the Antarctic, the standard-type killer whales appear to specialize on minke whales, one smaller type eats mostly seals, and yet another small form appears to be a fish-eater (Pitman and Ensor 2003).
Systems: Marine

Threats [top]

Major Threat(s): Killer whales have been exploited at low levels in several regions world-wide (Jefferson et al. 1993). Norwegian whalers in the eastern North Atlantic took an average of 56 whales per year from 1938 to 1981. The Japanese took an average of 43 whales per year along their coastal waters from 1946 to 1981. The Soviets, whaling primarily in the Antarctic, took an average of 26 animals annually from 1935 to 1979 and then took 916 animals in the 1979/80 Antarctic season (Dahlheim and Heyning 1999; Reyes 1991). Killer whales are still taken in small numbers in coastal fisheries in Japan, Greenland, Indonesia, and the Caribbean islands (Reeves et al. 2003).

Fishermen in many areas see killer whales as competitors, and intentional shooting of whales is known to occur. This problem is especially serious in Alaska, where depredation of longline fisheries is extensive (Jefferson et al. 1993; Yano and Dahlheim 1995; Donohue et al. 2003). Depredation of long-line catches appears to be a recent and increasing phenomenon, and now occurs in many regions (e.g., Aleutian Islands Alaska, South Georgia, Crozet Island, and several other southern ocean island areas, Australia, and other locations in the south Pacific).

During the period 1976-1988, 59 whales were captured alive off Iceland, of which 8 were released, 3 died and 48 (an average 3.7 per year) were exported to aquaria (Reyes 1991). Live-captures of several killer whales have also taken place in Japanese waters (Reyes 1991). Bycatch in trawl and driftnet fishing operations occur, but are considered rare (Dahlheim and Heyning 1999).

Persistent bio-accumulating contaminants have recently been found to present a serious potential risk to some killer whale subpopulations. Ross et al. (2000) report that total PCB concentrations were very high in three killer whales subpopulations (2 resident and 1 transient) frequenting the coastal waters of British Columbia, Canada. Transient killer whales were particularly contaminated due to their high trophic position in the marine ecosystem. PCB levels in most killer whales sampled were greater than levels established at which adverse effects occur in harbor seals, suggesting that the majority of free-ranging killer whales in this region are at risk of toxic effects. The southern resident and transient killer whales of British Columbia and Washington can be considered among the most contaminated cetaceans in the world (Ross et al. 2000).

Habitat disturbance may be a matter for concern in areas inhabited by killer whales and supporting whale-watching industries (Reyes 1991). Moving boats can disrupt activities such as foraging and resting, and underwater boat noise could affect social and echolocation signals of the whales or otherwise interfere with foraging (Erbe 2002; Williams et al. 2002). For example, close approaches by whale-watching vessels have been shown to result in avoidance responses by resident killer whales in British Columbia, which may result in energetic costs for whales frequently subjected to whale watching activity (Williams et al. 2002, 2006). Fast-moving boats in the proximity of killer whales also present a risk of collision or injury from propellers. Visser (1999) reports on propeller scars observed on killer whales in New Zealand and their possible causes of mortality.

Large-scale catastrophic oil spills have the potential to cause significant mortality of killer whales. The Exxon Valdez oil spill in Alaska was strongly correlated with the subsequent loss of several whales from a pod that had been seen swimming through light oil slicks early in the spill (Dahlheim and Matkin 1994). Oil spills may also have an indirect effect by reducing prey abundance.

There have been large-scale reductions in predatory fish populations (Myers and Worm 2003; Baum et al. 2003) and over-fishing and collapse of several important “prey” fish stocks world-wide (Jackson et al. 2001). There have also been dramatic declines in marine mammal populations throughout the world. The effects of such reductions in prey populations (both fish and marine mammal) and subsequent ecosystem changes on world-wide populations of killer whales are unknown but could result in population declines.

Due to their dietary specialization, some populations of killer whales could be especially vulnerable to a reduction of their food supply. In British Columbia and Washington State, many salmon stocks have significantly declined as a result of over-fishing, habitat degradation and reduced ocean survival. This is likely to affect fish-eating resident killer whale populations in that region (Ford et al. 2005). Mammal-hunting killer whales in British Columbia likely experienced periods of reduced prey availability due to depletion of pinniped populations prior to 1970 (Ford and Ellis 1999). The depletion of the Mediterranean bluefin tuna stock is considered a source of concern for the survival of the Gibraltar killer whales (Cañadas and de Stephanis 2006).

Predicted impacts of global climate change on the marine environment may negatively affect certain killer whale subpopulations more than others through changes in prey availability (see e.g. Learmonth et al. 2006).

Conservation Actions [top]

Conservation Actions: The species is in Appendix II of CITES and Appendices I and II of CMS. The eastern North Atlantic as well as the eastern North Pacific subpopulations are included in Appendix II of CMS.

Further studies on subpopulation structure, abundance and life history are needed for most regions. Regional subpopulations of killer whales can be small and highly specialized, and therefore vulnerable to over-exploitation and habitat deterioration. Several small subpopulations have already been recognized as having a high risk of extinction. Many similar small subpopulations may exist worldwide but have not yet been fully identified and described. There are likely several subpopulations that qualify for a threatened category, and steps should proceed to assess their status.

Citation: Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L. 2013. Orcinus orca. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 31 July 2014.
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