Ordinarily, turtle-headed sea snakes have black skin with white bands or blotches. In a recent study conducted at the Pacific island of New Caledonia, however, it was discovered that snakes living on reefs near the city or military activity were almost pure black. It turns out that they've evolved to shed pollutants that bind to the melanin in black skin.
Study lead author Claire Goiran, of the University of New Caledonia, already knew that the darker feathers of pigeons in Paris store more zinc than lighter feathers. That zinc enters their bodies from the urban environment, binds with the melanin in their dark feathers, and is then shed along with them.
In order to determine if something similar was happening with the snakes, she and her colleagues analyzed their sloughed skins. Sure enough, it was found that the skins of darker "urban-industrial" snakes contained more trace elements of pollutants – including arsenic and zinc – than the skins of normally-colored snakes from more pristine areas.
Additionally, the darker the skin of the urban-industrial snakes, the higher the concentration of pollutants. What's more, those snakes also shed their skin more often than their black-and-white counterparts. All in all, an effective way of drawing pollutants out of their bodies, then getting rid of them.
A paper on the research was recently published in the journal Current Biology.