Killer Whale

The **killer whale** or **orca** (*Orcinus orca*) is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. Killer whales have a diverse diet, although individual populations often specialize in particular types of prey. Some feed exclusively on fish, while others hunt marine mammals such as seals and dolphins. They have been known to attack baleen whale calves, and even adult whales. Killer whales are apex predators, as there is no animal that preys on them. Killer whales are considered a cosmopolitan species, and can be found in each of the world's oceans in a variety of marine environments, from Arctic and Antarctic regions to tropical seas—killer whales are only absent from the Baltic and Black seas, and some areas of the Arctic Ocean.

Killer whales are highly social; some populations are composed of matrilineal family groups (pods) which are the most stable of any animal species. Their sophisticated hunting techniques and vocal behaviours, which are often specific to a particular group and passed across generations, have been described as manifestations of animal culture.

The International Union for Conservation of Nature currently assesses the orca's conservation status as data deficient because of the likelihood that two or more killer whale types are separate species. Some local populations are considered threatened or endangered due to prey depletion, habitat loss, pollution (by PCBs), capture for marine mammal parks, and conflicts with human fisheries. In late 2005, the Southern Resident Killer Whales, the population that inhabits British Columbia and Washington state waters, were placed on the U.S. Endangered Species list.

Wild killer whales are not considered a threat to humans, but there have been cases of captive orcas killing or injuring their handlers at marine theme parks. Killer whales feature strongly in the mythologies of indigenous cultures, with their reputation ranging from being the souls of humans to merciless killers.

## Description

A typical killer whale distinctively bears a black back, white chest and sides, and a white patch above and behind the eye. Calves are born with a yellowish or orange tint, which fades to white. It has a heavy and robust body with a large dorsal fin up to 1.8 m (5.9 ft) tall. Behind the fin, it has a dark grey "saddle patch" across the back. Antarctic killer whales may have pale gray to nearly white backs. Adult killer whales are very distinctive and are not usually confused with any other sea creature. When seen from a distance, juveniles can be confused with other cetacean species, such as the false killer whaleor Risso's dolphin. The killer whale's teeth are very strong and its jaws exert a powerful grip; the upper teeth fall into the gaps between the lower teeth when the mouth is closed. The front teeth are inclined slightly forward and outward, thus allowing the killer whale to withstand powerful jerking movements from its prey while the middle and back teeth hold it firmly in place.

Killer whales are the largest extant members of the dolphin family. Males typically range from 6 to 8 metres (20 to 26 ft) long and weigh in excess of 6 tonnes (5.9 long tons; 6.6 short tons). Females are smaller, generally ranging from 5 to 7 m (16 to 23 ft) and weighing about 3 to 4 tonnes (3.0 to 3.9 long tons; 3.3 to 4.4 short tons). The largest male killer whale on record was 9.8 m (32 ft), weighing 10 tonnes (9.8 long tons; 11 short tons), while the largest female was 8.5 m (28 ft), weighing 7.5 tonnes (7.4 long tons; 8.3 short tons). Calves at birth weigh about 180 kg (400 lb) and are about 2.4 m (7.9 ft) long. The killer whale's large size and strength make it among the fastest marine mammals, able to reach speeds in excess of 56 km/h (30 kn). The skeleton of the killer whale is of the typical delphinid structure, but is more robust. Its integument, unlike that of most other dolphin species, is characterized by a well-developed dermal layer with a dense network of fascicles of collagen fibers.

Killer whale pectoral fins, analogous to forelimbs, are large and rounded, resembling paddles. Males have significantly larger pectoral fins than females. At about 1.8 m (5.9 ft) the male's dorsal fin is more than twice the size of the female's and is more of a triangular shape—a tall, elongated isosceles triangle—whereas hers is shorter and more curved. Males and females also have different patterns of black and white skin in their genital areas. Sexual dimorphism is also apparent in the skull; adult males have longer lower jaws than females, and have larger occipital crests.

An individual killer whale can often be identified from its dorsal fin and saddle patch. Variations such as nicks, scratches, and tears on the dorsal fin and the pattern of white or grey in the saddle patch are unique. Published directories contain identifying photographs and names for hundreds of North Pacific animals. Photographic identification has enabled the local population of killer whales to be counted each year rather than estimated, and has enabled great insight into lifecycles and social structures.

Occasionally a killer whale is white; they have been spotted in the northern Bering Sea and around St. Lawrence Island, and near the Russian coast. In February 2008, a white killer whale was photographed 3.2 km (2.0 mi) off Kanaga Volcano in the Aleutian Islands. In 2010, the Far East Russia Orca Project (FEROP), co-founded and co-directed by Alexander M. Burdin and Erich Hoyt, filmed an adult male nicknamed Iceberg .

Killer whales have good eyesight above and below the water, excellent hearing, and a good sense of touch. They have exceptionally sophisticated echolocation abilities, detecting the location and characteristics of prey and other objects in their environments by emitting clicks and listening for echoes, as do other members of the dolphin family. The mean body temperature of the orca is 36 to 38 °C (97 to 100 °F). Like most marine mammals, orcas have a layer of insulating blubber ranging from 7.6 to 10 cm (3.0 to 3.9 in) thick beneath its skin. The heart beats at a rate of about 60 beats/min when the orca is at the surface, dropping to 30 beats/min when submerged.

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