The herds of bison, antelope and elk that once roamed the prairies have vanished, but a few mountain sheep still graze on the grass-covered mesas in inaccessible portions of the Bad Lands.
In the mountains of British Columbia are the bighorn or Rocky Mountain sheep and the Rocky Mountain goat, while the saddleback and white mountain sheep have recently been discovered in the northern Cordillera.
The policy of the government which protects game, both in the park and in the surrounding national forests, has induced elk, deer, antelope, mountain-sheep, bears, porcupines, coyotes, squirrels, gophers and woodchucks to take shelter here.
The distribution of life-zones is primarily a matter of altitude and corresponds to that of the isotherms. The mountain goat and mountain sheep live in the Sierran upper-land, though long ago well-nigh exterminated.