Winter Extremes

Yellowstone is full of many wonderful, unique animals. Many of them have developed very unique ways to survive the extreme Yellowstone winters.

Take the Bison for instance. How does the largest North American mammal survive the subzero temperatures of Yellowstone?

It all starts with the first green grasses of summer. It will take the bison all summer and fall to build up enough fat reserves to have a chance at winter survival. Heavy snows and the extreme low temperatures deplete their fat reserves at an alarming rate. It doesn’t help that the grasses available under a blanket of winter snow have the nutritional value of cardboard. One way they insure their survival is by conserving as much energy as possible during the winter months. Using up too much energy decreases their chances of making it til spring.

The second thing that bison have to do to survive winter is stay warm. Bison grow a winter coat of woolly underfur with coarse guard hairs that protects them from the elements. It's key for surviving the extreme low temperatures of the Yellowstone winters. There is speculation that bison may not begin to feel cold until it gets to 30 below or more.

While bison must store up all the energy they can to survive winter one of the smallest North American mammals needs to eat every day during winter in order to survive.

The Ermine, also known as the short-tailed weasel or stoat, is a cute, color-changing weasel. In winter their fur turns completely white with the exception of the black tip on the tail. It’s one of the most dense furs of any mammal on earth. They have a body weighing just under half a pound and a body diameter about the size of a fifty cent piece. Their metabolism burns through calories so fast that the ermine is constantly in search of its next meal. These lightweights are pound-for-pound one of the most successful predators in North America, sometimes taking down rabbits twice their size.

Many animals in Yellowstone tend to either migrate or hibernate to cope with winters extremes. Then there are those like the bison and ermine that are able to adapt, making Yellowstone in winter an even more extraordinary place.

Ed