Based on their morphology and behavior have described several types of killer whale, which are based on their mitochondrial DNA and some have proposed that are species different or failing that, at least it's different races.
In the 1970 and 1980, research on the west coast of Canada and the United States identified three types of orca: residents, transients and offshore. Although these populations share parts of their range, show considerable genetic difference which shows they cross each other. The three types differ substantially in their ecology, behavior and morphology. The types are described below:
Orcas are most frequently observed in coastal areas east of the North Pacific off the coast of Canada and the United States , live in this area throughout the year and migrate to less distance than bystanders. In these four communities are known the area: the south, the north, southern Alaska and western Alaska. They feed primarily on fish, especially salmon , and sometimes squid .They live in complex family groups (called a pod ) composed of six to sixty individuals. They differ from other types, transient and offshore, in the shape of the dorsal fin that curves and rounded at the tip and patterns of vocalization. Communities that are part of this type of orca are highly inbred , meaning that mating only occurs between individuals within its community.
Such herds is associated orca smaller than residents, mobilized more frequently in smaller groups to ten copies show a less rigid social organization that residents and do not eat fish, their diet is mainly based on marine mammals. It has a wider distribution range that residents and migrate to greater distances than this. Vocalizations have less varied, less complex dialects and emit sounds only 5% of the time. It also shows morphological differences with respect to the residents and sea, as opposed to these, have a triangular dorsal fin with pointed toes.
This group was described in 1988, when they were observed in the open sea. Until recently it was believed that his diet consisted mainly of fish and thought to be due to the presence of scars and nicks on the dorsal fins similar to those observed in the transients, also feed on marine mammals and possibly sharks. According to a study published in 2011, his diet seems to be based mainly on sharks and frequently do species of the genus Somniosus . This type of killer whale is slightly smaller than the other two types and the tips of their dorsal fin, as well as the residents, are rounded.
Orcas residents and pedestrians share some areas, but generally avoided. According to the analysis of DNA samples from skin, found that both groups were separated for at least 10,000 years.
In Antarctica, described four types of orca:
Type A is the average size of a whale with a pattern of white and black, and an eye patch of medium size. It lives in open waters and feeds almost exclusively on southern minke whales.
Type B is smaller than type A, the white patch on the eye region is large, the whites have a yellowish tinge and dark areas rather than have a grayish black. It has a light gray stain that is distributed from head to dorsal fin. Their diet consists mainly of seals.
Type C: the killer of this type is the smallest and those living in larger groups. The white patch on the eye region is oriented obliquely and forward, instead of being parallel to the axis of the body. Like Type B has a large gray patch on the back and white areas have a yellowish tinge.
Type D: was described based on photographic analysis of a mass stranding in 1955 in New Zealand and observations from 2004.This is the most different in appearance and orca can be recognized immediately by its very small eye patch. Its range appears to be circumpolar on Antarctic waters between 40 ° and 60 ° latitude south. The herds appear to be large with an average of 17.6 members and a range of 9-35 animals.
The B and C live close to the ice sheets and yellowing of the whites is due to the presence of algae diatoms in Antarctic waters.
Mitochondrial DNA studies seem to support the hypothesis that the types of killer whales in Antarctica are described in different species recently separated, but the results are inconclusive. Other studies of complete mitochondrial sequences suggest that the types B and Antarctic C could be recognized as different species, as well as passers-North Pacific. Under this assumption, the other subspecies orca would remain as pending additional data.
Orca populations in other parts of the world have not been studied in sufficient detail to distinguish other types. However, it seems to have similarities to the types described by comparing the dietary habits and social characteristics of the relationship they have. For example, the population that inhabits the waters of Norway and feeds on fish has a family structure similar to that of the resident orcas of North America , and killer whales that feed on mammals and birds in Argentina and the Crozet Islands are similar more passers-by.