Bison are built to survive and even prosper in the Northern Great Plains. They have lived here for at least 500,000 years through a couple of ice ages. The Rocky Mountain’s weather is not a serious problem to them as long as they can move. They tolerate severe cold and heavy snow as long as they can get to areas where grass is accessible to them. They may stand and tolerate heavy snow for a while then they will try to push through drifts to get to windblown ridges or lower elevations. Their patient tolerance of extreme weather conditions and powerful body structure give them an advantage, allowing them to survive very well.