This is a late post to this thread, but I wanted to add that the does in my area of south central Colorado have all dropped twins this year, and although we had one hell of a winter here, they don't seem to have been hurt by it. Actually, my area is heavily over populated with deer.
I am more concerned by the fact that the DOW has cut back the number of deer licenses, than with winter kill. If this over population is allowed to continue, CWD, or a hard winter, will do what the DOW is not taking care of.