Orcas or killer whales have a cospolitan distribution and several distinct populations or types have been docunted or suggested. Three to five types of orcas y be distinct enough to be considered different races， subspecies， or possibly even species (see Species proble. The IUCN reported in 2008，“The taxono of this genus is clearly in need of review， and it is likely that O. orca will be split into a nuer of different species or at least subspecies over the next few years.“ Although large variation in the ecological distinctiveness of different orca groups plicate sile differentiation into types. al-eating orcas in different regions were long thought likely to be closely related， but genetic testing has refuted this hypothesis.

Northern waters

North Pacific

Research off the west coast of Canada and the United States in the 1970s and 1980s identified the following three types:

Resident (fish-eating) orcas: The curved dorsal fins are typical of resident feles.

Resident: These are the st nly sighted of the three populations in the coastal waters of the northeast Pacific. Residents“ diets consist pririly of fish and sotis squid， and they live in plex and cohesive faly groups called pods. Fele residents characteristically have rounded dorsal fin tips that ternate in a sharp corner. They visit the sa areas consistently. British Coluia and Washington resident populations are angst the st intensively studied rine als anywhere in the world. Resident orcas can be divided into at least three distinct nities; northern， southern and southern Alaskan. Southern Alaskan resident orcas are distributed frosoutheastern Alaska to the Kodiak Archipelago and nuer over 700 individuals. These whales consist of two interbreeding clans distinguished by acoustic calls and whose ranges overlap. The northern resident nity lives in coastal and inland waters frosoutheastern Alaska to Vancouver Island. It consists of three clans and 16 pods and nuer over 300 orcas total. The southern resident nity generally inhabits the inland waters of southern British Coluia and Washington， but can be found in the outer waters off Vancouver Island， Washington， Oregon and California. They consist of one clan and three pods， and nuer less than 80 individuals and are listed as endangered.

Transient or Bigg”s: The diets of these orcas consist alst exclusively of rine als. They live in the sa areas as residents， but the two avoid each other. Transients generally travel in sll groups， usually of two to six anils， and have less persistent faly bonds than residents. Transients vocalize in less variable and less plex dialects. Fele transients are characterized by re triangular and pointed dorsal fins than those of residents. The grey or white area around the dorsal fin， known as the “saddle patch“， often contains so black colouring in residents. However， the saddle patches of transients are solid and unifory grey. Transients roawidely along the coast; so individuals have been sighted in both southern Alaska and California. Transients are also referred to as Bigg“s orca in honour of cetologist chael Bigg. The terhas bee increasingly n and y eventually replace the transient label. The transient ecotype is estited to have diverged 700，000 years ago. There are at least three different “stocks“ of transients off North Arica， the AT1 stock which occurs froPrince WilliaSound to Kenai Fjords， the Gulf of Alaska/Aleutian Islands/Bering Sea (GOA/AI/BS) stock and the west coast stock which ranges frosoutheast Alaska to California. AT1 is considered a depleted stock; it was affected by the Exxon Valdez oil spill and declined fro22 individuals to eight between 1989 and 2004. The GOA/AI/BS stock y nuer around 500 whales while the west coast transients nuer over 320 orcas with over 200 along southeast Alaska， British Coluia and Washington and over 100 orcas off California. California transients do not appear to interngle ch with those further north and west coast transients y be divided into sub-nities.

Offshore: A third population of orcas in the northeast Pacific was discovered in 1988， when a huback whale researcher observed thein open water. As their na suggests， they travel far froshore and feed pririly on schooling fish. However， because they have large， scarred and nicked dorsal fins reseling those of al-hunting transients， it y be that they also eat als and sharks. They have stly been encountered off the west coast of Vancouver Island and near Haida Gwaii. Offshores typically congregate in groups of 20–75， with occasional sightings of larger groups of up to 200. Little is known about their habits， but they are genetically distinct froresidents and transients. Offshores appear to be sller than the others， and feles are characterized by dorsal fin tips that are continuously rounded.

Separate fish-eating and al-eating orca nities also exist off the coast of the Russian Far East and Hokkaido， Japan. Russian orcas are nly seen around the Kahatka Peninsula and Coander Islands. Over 2，000 individual resident-like orcas and 130 transient-like orcas have been identified off Russia. At least 195 individual orcas have been cataloged in the eastern tropical Pacific， ranging froBaja California and the Gulf of California in the north to the northwest coast of South Arica in the south and west towards Hawaii. Orcas appear to regularly occur off the Galápagos Islands. Orcas sighted in Hawaiian waters y belong to a greater population in the central Pacific.

North Atlantic and adjacent

Orca tail-slapping in Vestfjorden， Norway

At least 15，000 whales are estited to inhabit the North Atlantic. In the Northeast Atlantic， two orca ecotypes have been proposed. Type 1 orcas consist of seven haplotypes and include herring-eating orcas of Norway and Iceland and ckerel-eating orcas of the North Sea， as well as seal-eating orcas off Norway. Type 2 orcas consist of two haplotypes， and inly feed on baleen whales.

In the diterranean Sea， orcas are considered “visitors“， likely frothe North Atlantic， and sightings bee less frequent further east. However， a sll year-round population exists in the Strait of Gibraltar， which nuered around 39 in 2011. Distinct populations y also exist off the west coast of tropical Africa， which have generalized diets.

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