Yes Virginia, There are Black Squirrels in Massachusetts!
By Chris Williams on October 27, 2014.
I swear I saw a black squirrel in our yard. It was about the same size as a gray squirrel. Is there such a thing as a black squirrel or did this guy roll in a coal bin? V. M., Amherst, MA
Yes, there are black squirrels but they are really eastern gray squirrels in formal dress. There are normal variations in the coat color of gray squirrels, but the black squirrel is the melanistic form of the gray squirrel. The black coat results from a genetic mutation that causes excessive pigmentation. The mutation is recessive which means that both parents have to have the gene in order to produce a black squirrel baby. It doesn’t happen often.
Where Can I See a Black Squirrel?
Consider yourself lucky to have seen a black squirrel. This black morph doesn’t occur everywhere. Black squirrels can be found throughout the gray squirrel’s range which is mostly the eastern U.S., but they are very regional. Most people in the East will never see a black eastern gray squirrel. The hotbed for black squirrels is in and around Washington, D.C. where supposedly they escaped from the National Zoo in the early 1900’s.
As the story goes, in 1902 and 1906, 18 black squirrels were delivered to the Zoo from Canada, where they are common. By 1923, black squirrels were being noted outside of the Zoo grounds but still inside the Capital Beltway. Now there are reports of black squirrel sightings for at least 30 miles outside of D.C. in any direction. Black squirrels, of course, interbreed with other gray squirrels (they don’t know they’re different). These suburban squirrels could be offspring of the original zoo squirrels, or from a natural occurrence of melanism in squirrel populations, or from more recent black squirrel introductions.
Black squirrels occur both in New Hampshire and Massachusetts. In Massachusetts, there are established populations of black squirrels in 60 cities and towns, including Springfield and scattered throughout suburban Boston. The Stanley Park preserve in Westfield, Massachusetts, has a colony of black-phase gray squirrels that are believed to be descended from a pair that were brought from Michigan in 1948. Black squirrels that are seen in the areas of Southwick, Springfield, and Amherst are likely descended from the Westfield squirrels.
Why Are Black Squirrels in Some Areas and Not Others?
The process of natural selection determines whether black squirrel morphs will survive and reproduce in any one area. It’s been recognized that black squirrels seem to be more common in urban and suburban areas. One theory is that they survive better than their gray relatives in areas with vehicles because motorists try harder to avoid hitting them (we all know how common dead squirrels are on the road). But that hypothesis hasn’t been proven. A second, more plausible theory is that black squirrels survive better in cities because there are fewer natural predators. In areas with predators such as hawks, black squirrels are more likely to be picked off than the more camouflaged gray squirrels.
It’s believed that the black morph is more common in northern regions of the U.S. (and into Canada) because the black coat allows the squirrels to absorb more heat from the sun in the winter which means greater survival.
[Source: Squirrels – The Animal Answer Guide. Richard W. Thorington Jr. and Katie Ferrell]
Photo credit: Bobolink / Foter / CC BY