Which whale species is entirely white as an adult?

Which whale species is entirely white as an adult? The answer is the beluga whale. The beluga, Delphinapterus leucas, is an Arctic and sub-Arctic toothed whale whose adult skin is completely white or whitish-gray.

Beluga calves are not born white. They usually begin life gray or blue-gray and gradually lose their pigmentation as they mature, commonly reaching their distinctive adult color at about seven years in females and nine years in males. The pale skin helps camouflage belugas against Arctic sea ice.

Belugas are specially adapted to life beneath frozen seas. Unlike most whales and dolphins, they have no dorsal fin, which makes swimming under ice easier. They also have a flexible neck and a rounded forehead containing a large, deformable melon used in echolocation. Their high-pitched calls have earned them the nickname “sea canaries.”

The narwhal is the beluga’s closest living relative, but adult narwhals are mottled gray and are famous for their long tusks. Humpback and gray whales remain gray or dark-colored, so they are not plausible adult-white alternatives.