The park gets about 16 inches of precipitation a year and has seen temperatures from 116 degrees to 40 below. Bison winter here without migrating, and their wallows catch the rain that other plants depend on. It is a thin living, and the grass is built for it.
This ground lives on about sixteen inches of rain and snow a year. Most of it falls in the warmer months. Temperatures here have run from one hundred sixteen degrees down to forty below. Bison don't leave for any of that. Their winter coats grow so thick that snow sits on top and never touches the skin. They use those huge heads to plow it aside and graze. Most animals turn their backs to the wind. Bison face into a coming storm. They change the ground, too. A wallow is a hollow worn by bison rolling in the dirt. It collects rain, and plants that need more water can grow there. On sixteen inches a year, even that much water changes what grows.
Photo: National Park Service, Wind Cave National Park, South Dakota, about 1950, National Archives 285992, public domain, cropped · Public domain