An Animal to Admire

Bison are incredibly well equipped to survive the harsh winters of Yellowstone National Park and the Great Plains. Their heavy coats protect them from temperatures as low as -25 degrees F. Their bodies are so well insulated against the cold that snow and freezing rain that land on them don't melt. This is why bison are often seen with faces totally covered with snow or frozen moisture as they exhale. Bison use their massive heads to sweep aside deep snow as they search for the grass below. 

Their adaptations notwithstanding, about nine of every 100 bison will die during the winter. Most of these were ill, injured, old or in poor condition at the start of winter. Young bison facing their first winter have a higher mortality rate, with between 20 and 40 of every 100 not surviving. Major causes of death include accident, lack of food and predation.