Orcas get their nickname "killer whales" from their reputation of being ferocious predators, exhibiting almost hateful behaviors when toying with their prey. Interestingly, however, killer whales are actually very large dolphins, reaching lengths of 33 feet (10 m) and weights of at least 10 metric tones (22,000 pounds).
They are also extremely curious and often approach people to investigate. Their intelligence is likely both a result of and a driver of their complex social structures. They generally live in small groups and organize complex, group behaviors when mating and hunting. They are intelligent, playful, powerful animals – a worrisome combination if you happen to be their preferred prey. Different orca populations specialize on different prey types, including large bony fishes; seals, sea lions, and other large marine mammals; and penguins; among other things.
Though all orcas, worldwide, are considered to be members of the same species, there are several known populations that have slightly different appearances, sizes, and behaviors. These include populations that are somewhat territorial and do not migrate long distances (the so called resident populations) and those that are more migratory in nature (the so called transient populations). Furthermore, some transient populations stay near the coast and overlap with resident populations, while others are oceanic. Some orca scientists believe that these populations may represent different species, and recent research suggests that there may be as many as 16 different species. To date, the new species have yet to be described, and the cosmopolitan species Orcinus orca is considered to cover all individuals around the world, regardless of behavior or appearance.
Orcas are the most widely distributed cetaceans (whales, dolphins and porpoises) and can be found in every ocean forming social groups consisting of a 3 to 20 members that tend to stay together over multiple generations. Female orcas are one of only three species that go through menopause, the other two being short-finned pilot whales and humans. Orcas have the most diverse diet of all cetaceans, eating anything from salmon to seals, whales and squid.
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