I think the snow brings an urgency to eat for the deer. They definatly key on the food sources, digging for acorns up here in N Wisc. As the snow gets deeper (1' and more) they start to head for evergreen cover. Around here they "yard up" in cedar thickets. They also use spruce/balsam fir as a transition zone/bedding area before they hit the traditional yards. I've also seen them take cover in a spruce thicket during snow storms. I don't know how they survive the harsh winters up here with -30 and 100" or more of snow. They are amazing creatures...