Humpback whale populations across the world may actually be separate subspecies, a new genetic study reveals.
Though the expert swimmers make the longest migrations of any mammal, the subpopulations in the North Pacific, North Atlantic and the Southern Hemisphere oceans stick to separate routes.
"Humpback whale populations are actually more isolated from one another than we thought. Their populations appear separated by warm equatorial waters that they rarely cross," study co-author Jennifer Jackson, a researcher with the British Antarctic Survey, said in a statement.
This isolation may explain why the northern swimmers tend to have darker coloring on their underbellies and tails than their southern counterparts. The results suggest the different populations are evolving independently. [In Photos: Tracking Humpback Whales]
As a result, the populations in the three oceans should be classified as distinct subspecies, the researchers found.
Long-distance swimmers Humpback whales (Megaptera novaeangliae) usually feed at high latitudes, then make their way toward the equator to breed - a journey that can cover 3,000 miles (5,000 kilometers). The whales also seem to travel in strikingly straight lines, rarely veering off course by more than 1 degree, though exactly how they accomplish this amazing navigation remains a mystery.