Neat looking critter! Looks like he injured his tail and all the hair grew back white!
(Is anybody doing a squirrel study over your way??? When I worked on a fox squirrel study, we dyed their hair using Lady Clairol Ultra Blue and Miss Clairol Velvet Black (funny how I can still remember that) so that we didn't necessarily have to get our hands on them to recognize (recapture) an individual squirrel.) But that one looks more like the hair got stripped off (maybe by a hawk or something).