Orcas are considered a single species. Should they be?

A new study suggests that two populations of North Pacific killer whales are distinct enough to be considered separate species.

Killer whales are among the most cosmopolitan creatures on the planet, swimming in all the world's oceans. They patrol the frigid waters near both poles and appear periodically in the tropics, in places from West Africa to Hawaii.

Although their Their habitats and habits vary widely, all killer whales are considered part of a single global species: Orcinus orca. (Despite their common name, killer whales are actually part of a family of marine mammals known as oceanic dolphins.)

Now scientists have relied on decades of research to suggest that two populations of killer whales often seen off the Pacific coast of the United States and Canada are actually so different from each other — and from other orcas — that they should be considered separate species.

In a paper published Tuesday in the journal Royal Society Open Science, scientists proposed giving new species designations to two groups of animals, one known as resident killer whales and the other often called Bigg's killer whales. Although both types live in the eastern North Pacific, they have different diets: resident orcas eat fish, with a particular predilection for salmon, while Bigg's orcas hunt marine mammals such as seals and sea lions.

The proposal documents many other behavioral, physical and genetic differences between the two orca populations, which evolve from each other to the "These two types are genetically two of the most distant types in the world," Phillip said. Morin, a geneticist at the Southwest Fisheries Science Center of the National Oceanic and Atmospheric Administration, or NOAA, and an author of the study. “They don’t just behave differently. They're really on these evolutionary trajectories that we think of as different species. »

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