Mange. There is this little mite around here, I'm too lazy to go over to wikileaks and look up it's secret name, but sure as hell a latin handle exists for it. This mite is jumping on the squirrel's, the result is it looks like the squirrels here are into punk, or meth. Or maybe they're into the ridiculous craze of full body shaving like some humans, probably got hooked looking through the window at a porn show. *
Two years ago was the first time the mange hit my population of climbers. This year it's back. It is ugly, thin tails, patches of hair gone from the body, sometimes they lose all of it. Sunburns follow, then they disappear, I assume they die or fall prey. These mites climb aboard during Sherpa to Sherpa contact. The hair supposedly grows back if the mites leave, but if they live into the winter without a good coat they don't survive.
* Forget the squirrel for a minute, as a matter of human body fact, pubic hair signals sexual maturity, hairlessness means either the person is a child, or advanced elderly, not exactly my goal for a roll in the hay, so lay off shaving your guters)