An ant that disappears into the forest floor, a bird that demands attention from mates—for these animals, an inky black ...

An ultra-rare all-black penguin has been spotted on South Georgia Island, standing out among its more typical black-and-white buddies by bucking the tuxedo trend with an entirely black body.

They are different not in color but in lip shape. The black rhino has a pointed upper lip, while its white relative has a squared lip. The difference in lip shape is related to the animals' diets.