Black squirrels may increase in a certain area due to natural selection because of the ground below it being dark so the squirrels would adapt to the terrain, making them harder to see by predators. EXAMPLE: if a light fur colored squirrel is on a dark terrain, an Owl or Large bird could easily see the color differentiation and notice that it is a small land organism (prey). So the squirrels kin would evolve in the sense that they would have darker fur to match their inhabitance
