Actually it is an Eastern Grey Squirrel. They have different color phases including black. We saw this one in the VanDusen Botanical Garden in Vancouver. It probably migrated from Stanley Park where the Eastern Grey Squirrels were introduced in 1909.
Beautiful fellow. I never see any of this color around here; just the sleek grey & brown ones. Once when I was in Colorado I saw a black one, though I think it was a different type than this -- it had tufted ears and was about the size of a small cat and was terrifically shy. Nice shot.