The turtle-headed sea snake usually sports beautiful bands of alternating black and white. But for decades, researchers have been puzzled by populations living near Pacific Ocean cities that seem to have lost their stripes.

Now a new study may finally have an answer: The pigment in black skin may help city snakes rid themselves of industrial pollutants. (See what it's like to live in the world's most polluted city.)

By collecting shed skin from turtle-headed sea snakes in a variety of habitats, scientists discovered that all-black, urban snakes had higher concentrations of trace elements such as arsenic and zinc than did snakes far from cities. Importantly, the team found the same phenomenon in skin samples from another black-and-white banded snake,