I think the winter kill and summer drought are part of it. There was an article awhile back about the longest Mule deer migration, and I think that area was right through the migration route, but I am not totally sure. They were migrating up into the Hoback river area, and the Wyoming range mule deer have had it rough for a few years. There was some disease, the wolves, cats, hunting pressure, road kill, etc. There was a topic on here about that to search also. Lots of good posts I learned lots. The game and fish web-site has a lot of articles on the Wyoming range deer herd. It doesn't seem like the same herd, but I guess the deer have really been migrating a long ways. Also there was a lot of oil and gas in that general area that has slowed down a little. They have taken steps to reduce roadkill north of that area. I have heard that populations are doing better there with the steps taken, but a full recovery is still a few good years off it sounds like. Not really an answer, but maybe some places to look.