The adults rub against any available object and wallow on the ground to rid themselves of their molting pelage, and to scratch themselves when insects make them itch. When telegraph lines first crossed the prairies, many were knocked down by bison rubbing and scratching. During the winter the bison are split into two separate groups. The bull group has 5- 20 members. Both groups search for exposed grass to feed on.
Bison use their heads, horns, and powerful necks to clear away the snow that covers the food supply.
When water is difficult to find, they eat snow. Their thick coats and heavy layers of fat protect them from the cold temperatures. During blizzards, bison huddle together for warmth. Bulls often take shelter in trees, but the other group often tries to resist the wind in the open where they are more likely to find nourishing grass. At this time, the bison are building fat for the winter.