The killer whale (Orcinus orca), commonly referred to as the orca and, less commonly, blackfish, is the largest species of the dolphin family. They are found in all of the world's oceans, from the frigid Arctic and Antarctic regions to tropical seas. Killer whales as a species have a diverse diet, although populations often specialize in particular types of prey. Some feed exclusively on fish, particularly salmon, while other populations hunt marine mammals such as sea lions, seals, walruses and even large whales. Killer whales are regarded as an apex predator as they have no natural predators.

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http://en.wikipedia.org/wiki/Killer_whale
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