Scientists Finally Figured out Why Some Squirrels Have Black Fur

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If you’re lucky enough to live in certain regions of the U.S. or the U.K., you may have spotted squirrels that are black instead of gray. These unusual animals have been a bit of a mystery, but now scientists have figured out why they have such an odd color.

Researchers at Anglia Ruskin University, Cambridge University and the Virginia Museum of Natural History worked together on a project to test squirrel DNA. They discovered that black squirrels are the product of interspecies breeding between the common gray squirrel and the fox squirrel.

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Fox squirrels are usually reddish-brown, but some of them carry a faulty pigment gene that turns their fur a darker shade. Scientists believe that a black fox squirrel joined in on a mating fenzy among gray squirrels and mated with a female, who then gave birth to a black squirrel.

There may be an evolutionary benefit to black fur that caused the gene to be passed down. Black fur could help squirrels absorb and retain more heat — an important benefit in colder regions.

Black squirrels remain rare, however. There is an estimated one black squirrel in every 10,000 squirrels.

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In certain limited regions, though, the black squirrels have become predominant. At Kent State University in Ohio, for example, 10 black squirrels were released by students after they were captured by wildlife authorities, and they now populate the entire campus.