Why do whales migrate? They return to the tropics to shed their skin, scientists say

Killer whales in Antarctica, as shown here, often display a yellow coloration due to diatom accumulation on their skin, evidence that they are not sloughing skin in frigid waters. Image collected by John Durban (NOAA Fisheries) and Holly Fearnbach (SR3) using a remotely controlled hexacopter drone at 100-foot altitude, authorized by NMFS research permit 19091 and Antarctic Conservation Act Permit 2017-029. Credit: John Durban/NOAA Fisheries and Holly Fearnbach/SR3

Whales undertake some of the longest migrations on earth, often swimming many thousands of miles, over many months, to breed in the tropics. The question is why—is it to find food, or to give birth?

In a research paper in Marine Mammal Science, scientists propose that whales that forage in polar waters migrate to low latitudes to maintain healthy skin.
“I think people have not given skin molt due consideration…

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