A lot of the winter stress is the PROLONGED nature of it. The cumulative effects, if you will of the fall hunt leading into bitter cold and heavy snow shivering off all that fat and getting no replacement food calories. If they miss the -30 Dec-Jan temps they are well suited to handle spring snow depths. So far it would appear there was/is no cold. (and it never hits this late). This year they have bellies full of stuff, maybe not the best stuff but it beats the roots/rocks they eat when that's all that isn't white. Another month and the green up next to the highways will draw them like moths to a flame, that may take a few out, always does.