They're neat, aren't they? There is a high percentage of black squirrels on the grounds of the Bronx Zoo. In Jackson, MI I've seen some that are almost white.

Loads of them in the Berkshires of Massachusetts as well.

They are really neat little critters! Only problem I have seen with them is that sometimes they can be mean and chase off other kinds of squirels.

Black squirrels are no "meaner" than any other. They are the same species as the common grey squirrel, only difference is that they are a color mutation. So yes, like the greys, they will dominate smaller species, but one color is no more agressive than another.

The correct term would be melanism. It's an increased amount of black or nearly black pigmentation. I just learned about it yesterday ;)