Hey Woods Walker, thanks for the reply, that's a possibility that I never thought of. I don't really know either if what you described in horses would happen on a deer, but it's definitely an interesting idea.
It definitely looks like some kind rubbing is happening, due to the way the hair is broken off. It doesn't look like hair is just falling out, but that those spots are getting rubbed. Obviously there are plenty of things in the wild the deer can rub on, I'm just curious what is causing this specific kind of rubbing (assuming that its from rubbing). It occurs on such a specific spot on the deer, and not on all deer, but happens on deer all across the country, and again, in the exact same spots. Can't say for sure if it's only a buck thing or if it happens on does too, people don't seem to notice it on does, but then again, we don't taxidermy many does, so it could go un-noticed quite easily. Other ideas that came to mind are glands; are there glands there that are rubbed for marking purposes that nobody has every really heard of? A lot of people suggested ticks in one way or another, mainly that ticks congregate there and its from biting, scratching with the rears hoof, or rubbing on other objects because of the irritation on the skin.
I'm sure to most hunters this is very "who the heck cares?" kind of topic. To the taxidermists though that are wondering about this, it's a big deal in the sense that guys don't notice this damage to the hair when they drop a deer off, but it's the first thing a guy notices in the taxidermy shop when he comes to pick up his deer he hasnt seen in 10 months. First words out of his mouth are "what the heck happened to my deer? What did YOU do to it?" It happens in the woods, that much we've been able to narrow down. But it would be great to have an explanation for why it's happening, so when a customer walks into a taxidermist's shop and wants to know how that hair got damaged, the taxidermist can explain it better than " I don't really know, that's how it was when you brought it in". Plus, it's a part of deer behavior that would just be interesting to know more about.
Anyway, thanks again for the reply, I appreciate you taking the time to respond.