January 2, 2012
Killer whales distinctively bear a black back, white chest and sides, and a white patch above and behind the eye. Killer whales have a heavy and robust body with a large dorsal fin up to 2 meters (6.6 ft) tall.
Killer whales are the largest extant members of the dolphin family. Males typically range from 6 to 8 meters (20–26 ft) long and weigh in excess of 6 tones (5.9 long tons; 6.6 short tons). Females are smaller, generally ranging from 5 to 7 meters (16–23 ft) and weighing about 3 to 4 tones (3.0 to 3.9 long tons; 3.3 to 4.4 short tons). The largest male killer whale on record was 9.8 meters (32 ft), weighing over 10 tones (9.8 long tons; 11 short tons), while the largest female was 8.5 meters (28 ft), weighing 7.5 tons (7.4 long tons; 8.3 short tons).
The killer whale's large size and strength make it among the fastest marine mammals, able to reach speeds in excess of 30 knots (56 km/h).Killer whale pectoral fins are large and rounded, resembling paddles. Males have significantly larger pectoral fins than females. At about 1.8 meters (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.
Killer whales have good eyesight above and below the water, excellent hearing, and a good sense of touch. They have exceptionally sophisticated echo location abilities, detecting the location and characteristics of prey and other objects in their environment by emitting clicks and listening for echoes.
Population
Worldwide population estimates are uncertain, but recent consensus suggests an absolute minimum of 50,000 Local estimates include roughly 25,000 in the Antarctic, 8,500 in the tropical Pacific, 2,250–2,700 off the cooler northeast Pacific and 500–1,500 off Norway. Japan's Fisheries Agency estimated there were 2,321 killer whales in the seas around Japan.
Behaviour
Killer whales often raise their bodies out of the water in a behaviour called spyhopping.
Day-to-day killer whale behavior generally consists of foraging, traveling, resting and socializing. Killer whales are frequently active at the surface, engaging in acrobatic behaviors such as breaching, spyhopping, and tail-slapping. These activities may have a variety of purposes, such as courtship, communication, dislodging parasites, or play. Spyhopping, a behavior in which a whale holds its head above water, helps the animal view its surroundings.
The killer whale's intelligence, trainability, striking appearance, playfulness in captivity and sheer size has made it a popular exhibit at aquariums and aquatic theme parks. From 1976 to 1997, 55 whales were taken from the wild in Iceland, 19 from Japan, and three from Argentina. These figures exclude animals that died during capture. Live captures fell dramatically in the 1990s, and by 1999, about 40% of the 48 animals on display in the world were captive–born.
Captives occasionally act aggressively towards themselves, their tank mates, or humans, which critics say is a result of stress.
Tilikum, a captive killer whale born in the wild, has been involved in three fatalities including one in which he grabbed a trainer and pulled her underwater, eventually drowning her. Experts are divided as to whether the injuries and deaths caused by captive killer whales have been accidents or deliberate attempts to cause harm.
Information compiled from various sources
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