The last time we visited our aunt and uncle in Minnesota, we were mesmerized by the black and albino squirrels skittering around the backyard. Two years later, the yard still had a good population of squirrels, but the black ones were gone and just one albino remained.
There’s a surprising amount of literature devoted to coat color in gray squirrels. Black is apparently one of three color variants found in gray squirrels. As in other animals, albinism is rare, however, according to one article, albinism in squirrels can run in colonies. I remember one such colony in Verona Park, Verona, N.J., during the 1980s.