Killer Whale or Orca, largest member of the dolphin family. Killer whales occur in more parts of the world than probably any other cetacean (see Whale). They occur in all oceans, both in the open ocean and close to shore, but are more common in the colder, more productive waters of both hemispheres than in the Tropics. Resident populations may cover an area of several hundred square kilometers. Transient populations often move through an area rapidly, swimming more than 1000 km (more than 600 mi) along a shoreline in a matter of days.Killer whales are black or deep brown overall, with striking white patches above the eye and from the lower jaw to the belly, and a fainter grayish-white saddle patch just under and behind the dorsal fin. Males are somewhat larger than females, with mature females reaching lengths of up to 8.5 m (up to 28 ft), and mature males reaching lengths of up to 9.8 m (up to 32 ft). All killer whales have a prominent triangular dorsal fin in the middle of the back, but that of the adult male may grow to 1.8 m (5.9 ft) tall. The flippers of both sexes are large and oval, unlike those of any other toothed whale.
Killer whales may be solitary or live in groups of 2 to more than 50 animals. They feed on fish, squid, marine birds, pinnipeds (see Seal), and even other cetaceans. They generally cooperate during hunting, especially when feeding on large, warm-blooded animals such as penguins, seals, and porpoises. Killer whales have even been known to prey on blue whales, the largest species on earth. In most areas, killer whales have specialized feeding habits. In the Pacific Northwest of the United States and the Pacific Provinces of Canada, for example, resident populations feed mainly on salmon and other near-shore fishes, while transient populations feed primarily on harbor seals and porpoises. In several places in the southern hemisphere they habitually beach themselves as they rush ashore to take seals or sea lions in the turbulent surf zone, moving back to deeper water afterward.
Killer whales use echolocation to gather information about their surroundings—that is, they send out high-frequency clicks that bounce off prey and other objects and they interpret the returning echoes. Killer whales communicate by means of rapid-fire click trains that sound like rasps and screams, although when they are on the prowl for marine mammals, which have acute underwater hearing, they can be silent for hours at a time.
