Orcinus orca
Killer whales, also referred to as orcas, are a form of marine mammal. Killer whales are in fact, not whales,they are in the Delphinidae family, which includes dolphins.
Social Structure
Killer whales form groups or pods consisting of about four matrilines. Each matriline has one matriarch. Female whales are dominant in the pods, and can live up to 90 years, so each matriarch can travel with up to four generations of offspring. Males usually mate outside their pods. Clans are the next step in the social structures, which are two or more pods with similar dialects. After clans, communities are the next step, which are clans that interact, but don't share similar vocal patterns. Residents of pods stay with the same clan for their whole lives, but that is not always the case. Most males maintain a strong relationship with their mothers, but occasionally some males become "rovers," leave their pods and go join another pod containing more reproductive females.
Vocalizations
Like all cetaceans, killer whales depend on a series of squeals, clicks and whistles for communication and feeding. Residents of a pod all speak in similar calls, or dialect. Call patterns are distinctive between matrilines. Dialects are an important means of identity for groups.
Location
Killer whales are found in all oceans and most seas, but prefer cold waters, and stay closer to coastlines. Although sightings in warmer waters are possible and there are occasional off-shore pods. The highest concentrations are found off the coast of Antarctica, the Norwegian Coast, the coast of British Colombia, and the Gulf of Alaska.
SizeThe largest recorded male killer whale was 9.8 m (32 ft.) in length and weighed 10,000 kg (22,000 lb.) The largest recorded female was 8.5 m (28 ft.) and weighed 7,500 kg (16,500 lb.). The average male orca size is 19-22 ft, while females grow to about 16-19 ft. Killer whales are countershaded, the top surface is darker than the underbelly. When viewed from above the whale blends in with the dark ocean depths, and when viewed from above, the lighter belly surface blends with the lighter surface. Despite their name, Killer Whales are only called whales due to their size, not anatomy.
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DietOrcas are carnivores (only eat meat). Because there are several ecotypes of killer whales, their diets are usually linked with their geographical area. Orcas in a specific region can specialize in hunting different types of prey. Like most cetaceans, killer whales are not intimidated by larger animals and have been known to attack sharks. Killer whales generally prey on schooling fish, larger fish, rays, penguins, cephalopods, and mammals (i.e. leopard seals, sea lions, otters, porpoises, and some whales).
Food Chain
As shown in the picture below, the Killer Whale is at the top of the food chain in its ecosystem. The killer whale has no natural predators. the only plant life in the Orca's food chain is the algae that krill and protists eat.
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Human Ineractions
Whaling:
Killer whales have been interacting with humans since as early as the 18th century, when whaling was a popular sport. The earlier of known records of commercial hunting of killer whales date to the 18th century in Japan. During the 19th and early 20th centuries, the global whaling industry caught immense numbers of baleen and sperm whales, but largely ignored killer whales because of their limited amounts of recoverable oil, their smaller populations, and the difficulty of taking them. Killer whales have helped humans hunting other whales. One well-known example was in Eden, Australia, including the male known as Old Tom. Whalers more often considered them a nuisance, however, as they would gather to scavenge meat from the whalers' catch. Captivity: Killer whales are highly desired in aquatic theme parks due to intelligence, train-ability, and size. From 1976 to 1997, 55 whales were taken from the wild in Iceland, 19 from Japan, and three from Argentina. In captivity, they often develop pathologies, such as the dorsal fin collapse seen in 60–90% of captive males. Captives have vastly reduced life expectancies, on average only living into their 20s. Captives occasionally act aggressively towards themselves, their tank-mates, or humans, which critics say is a result of stress. |