20-25% of the squirrels in Minot ND are black. They are not native but were the result of someone trapping two dozen squirrels in LaCrosse WI, and sending them to Minot. The genetics were there and voila! In city parks, people tend to spend a greater effort feeding the darkest squirrels. Consequently, some of them get pretty danged entitled and ornery!
My parents had one that showed up at their bird feeder years back. Their habit was to read the newspaper out in the backyard after supper while they enjoyed a cup of coffee and a cookie or two. This squirrel got more and more daring as my dad would slip him peanuts. Eventually, this little guy would sit contentedly on the arm of dad's lawn chair and enjoy his evening snacks. If dad was too slow with the next peanut, the tree rat would pat him on the arm with one of his little paws. Once dad decided to ignore him to see what he'd do. After repeated pats, the squirrel took it upon himself to skitter up and dive headfirst into dad's shirt-pocket and serve himself.
Anywho, I forget the biologist that first posited the theory, so I cannot quote his exact name for the theory, but it states that the closer to the poles, the more likely individuals within a species will exhibit melanism (or darker coloration). The colder the climate, the better a dark coat is at solar gain, and the fewer calories are needed to stay warm. There is an advantage in that situation that a normal-colored member of the species would not have.
