We receive many questions about black squirrels. Two species of North American tree squirrels have black forms that occur naturally in certain parts of their ranges. The Eastern Gray Squirrel, a fairly small squirrel that occurs naturally throughout the eastern US and southeastern Canada and has been introduced into many western cities, is often black in northern parts of its range. In fact, in Canada it is often called the Black Squirrel. Black and gray individuals are often seen together, which makes some people think they're different species. The Eastern Fox Squirrel, which is larger and has orange- or yellow-tipped tail hairs, has a similar range but is absent from the northeastern US; in the South it is typically black, often with a white face and tail tip and sometimes ears.
The origins of black squirrels are obscure, but within the species’ natural ranges they probably reflect nothing more than normal geographic variation. Black (and white) squirrels seem especially prevalent in introduced populations, probably because the founders of those populations thought these forms were more attractive than the “normal” varieties. Some may be the result of selective breeding. The black squirrels in Kent, OH, were transplanted from Canada in the 1950s. Those in Marysville, KS, are believed to be descended from animals that escaped from a traveling carnival in the 1920s. There are albino populations in Olney, IL; Trenton, NJ; and Greenwood, SC.
Here are some Web links that you may find helpful:
an entertaining site on towns that promote themselves for their black squirrels
has some more information and links concerning black gray squirrels
Finally, you can learn more about these species in general on eNature:
We hope this helps,eNature Naturalists