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Killer whales are (at least) two species

Orca genetics highlights distinctions among groups

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Killer whales come in more varieties than anyone had realized, a new study of the predator’s DNA confirms. The finding could have important implications for marine conservation efforts, such as reducing the number of killer whales allowed to be caught when fishing in certain areas.

Until recently, scientists thought orcas that freely roamed the cold waters of the northern Pacific Ocean and the Bering Sea were a single species. But studies of the killer whales’ behavior and genetics suggested that there are at least two species — “resident” fish-eating orcas and “transient” mammal-eaters also known as Bigg’s killer whales (SN: 5/22/10, p. 8).

A new study of 462 killer whales, published July 11 in the Journal of Heredity, supports the division of northern Pacific orcas into two species. DNA analysis also indicates those species aren’t monolithic, Kim Parsons of the National Oceanic and Atmospheric Administration and colleagues report. Resident orcas fall into four genetically distinct subpopulations; at least five subgroups of transient killer whales ply the frigid seas.

Those subdivisions largely reflect the prey each group prefers, the researchers say.

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