Portal:Cetaceans/Selected Article/February, 2007

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 highly social and generally travel in stable, matrilineal family groups.

Orcas are versatile predators, with some populations feeding mostly on fish and others on other marine mammals, including large whales. 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 with no immediate relatives from a cladistic point of view, thus paleontologists believe that the orca is a prime candidate to have an anagenetic evolutionary history &mdash; that is the evolution of ancestral to descendant species without splitting of the lineage. If true, this would make the orca one of the oldest dolphin species, although it is unlikely to be as old as the family itself, which is known to date back at least five million years.

More on the Orca