White and black squirrels

Some animals we expect to be white—polar bears—and some are seasonally so: Arctic foxes and hares, stoats as ermine and ptarmigan on a snow-blasted mountain. Many seabirds are white across their underparts, which gives them, when bobbing on the water, a degree of camouflage from submerged predators when seen against the light of the sky. But white is less helpful in the wild when produced by albinism. White catches the eye of a predator as it darts effortlessly from branch to branch, tree to tree, fluffy-tailed and squirrel-like in every way except its snowy colour. A sight that resolves itself into an albino squirrel, with red beads for eyes. Some estimates conclude that, in Britain, about one in every 100,000 grey squirrels is albino, thanks to a rare gene inherited from the parents. Anecdotal evidence suggests that they’re most abundant in the South-east, particularly Kent and Sussex.

Black squirrels are also rare—and less visible—with numbers concentrated around Bedfordshire, Hertfordshire and Cambridgeshire. Their colouring is due to a piece of DNA missing from a pigmentproducing gene.