Orcas are considered a species. Should they be?
Killer whales are some of the most cosmopolitan creatures on the planet, swimming in all of the world's oceans. They patrol the frigid waters near both poles and periodically appear in the tropics, in locations from West Africa to Hawaii.Although their habitats and habits vary widely, all orcas are considered part of a single global species: Orcinus orca. (Despite their common name, orcas are actually part of a family of marine mammals known as oceanic dolphins.)Now, scientists have drawn on decades of research to suggest that two populations of killer whales often observed off the Pacific coast of the United States and Canada are actually so different from each other – and from other killer whales – that should be considered separate species.In a paper published Tuesday in the journ...