I recall reading that there about 30 different species of ground squirrels in North America - I've seen them on the banks of the Mackenzie River north of Norman Wells, but never 'gopher types' north of (roughly) Onoway in Alberta....not counting chipmunks, of course. I always thought their population had something to do with frost penetration, but maybe it's more related to soil types and the ease of digging. I've never seen a black ground squirrel, although I have seen (and shot) a pure black ground hog.