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The Orca or Killer Whale (Orcinus orca) is the largest species of the oceanic dolphin family (Delphinidae). It is found in all the world's oceans, from the frigid Arctic and Antarctic regions to warm, tropical seas.
Orcas are versatile predators with some populations feeding mostly on fish and other populations on marine mammals, including sea lions, seals, and large whales. There are up to five distinct Orca types, some of which may be separate subspecies or even species. Orcas are highly social; some populations are composed of matrilineal family groups which are the most stable of any animal species. The sophisticated social behaviour, hunting techniques, and vocal behaviour of Orcas have been described as manifestations of culture.
Although Orcas are not an endangered species, some local populations are considered threatened or endangered due to pollution, depletion of prey species, conflicts with fishing activities and vessels, habitat loss, and whaling. Wild Orcas are usually not considered a threat to humans. There have, however, been isolated reports of captive Orcas attacking their handlers at marine theme parks.
The Orca is the sole species in the genus Orcinus. It is one of thirty-five species in the dolphin family. Like the Sperm Whale genus Physeter, Orcinus is a genus with a single, abundant species. Thus, paleontologists believe that the Orca is a prime candidate to have an anagenetic evolutionary history, forming descendant species from ancestral species without splitting of the lineage. If true, this would make the Orca one of the oldest dolphin species. However, it is unlikely to be as old as the family itself, which is believed to date back at least five million years. Wikipedia |
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