Pilot whales are found in several parts of the world’s oceans, some in the Indian, Pacific, or even the North Atlantic oceans. However, a recent study published last June 3 in Molecular Ecology shows that two unique subspecies exist.

Two “forms” of pilot whales were described by Japanese whalers and scientists. One is the Naisa, which has a distinct square-shaped head and lives in Southern Japan, while the Shiro form has a round head and can be seen in northern Japan.

“You can’t manage animals globally without understanding their diversity. If you think of a group of animals as a single species, and it turns out they’re not, you could wind up accidentally losing an entire subspecies without knowing it,” Amy Van Cise, a postdoctoral scholar at Woods Hole Oceanographic Institution and lead author of the study, said in a statement.

Van Cise, along with other researchers, found the two distinct subspecies of short-finned pilot whales and explained that they are not separated by “any continental barrier, but instead by the vast expanse of the eastern Pacific Ocean.”

(Map by Natalie Renier, Woods Hole Oceanographic Institution)

“You would expect to see a different subspecies of whale in each ocean basin – the Atlantic, Indian, and Pacific. That’s pretty common. But what we found was that short-finned pilot whales in the Atlantic are the same sub-species as those living in the Indian Ocean and western Pacific,” she added.

Van Cise added that whales’ global distribution became limited around the central region of the Pacific, because there was little productivity and food was short in supply to support the whale population.

“It seems to have separated these groups of whales for long enough that they diverged into two different types,” Van Cise said. “That means continents and land forms may not have been as significant a barrier as we thought to this species’ evolution. Instead, the oceanic ‘desert’ in the Pacific might have been more important.”

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