At the golf course today there were several families of Western Gray Squirrels. According to the National Audubon Society Field Guide to the Pacific Northwest, these squirrels like to live in open oak woodlands. Since the course had many oaks (some of which got in the way of my golf ball), this seemed like a perfect habitat for them.
Previously I posted about the Eastern Gray Squirrel which is not a northwest native. Check out the photo in that post and then compare it to the one above. The easiest way for me to tell them apart is that the Western squirrel does not have any of the reddish brown coloring that the Eastern one has. Also, the ring around their eyes is different. The Western has a white ring while the Eastern has a reddish/tan coloring.