Bison in Yellowstone National Park
Bison, or American buffalo, takes a dust bath near the Yellowstone River, between Tower Junction and Lamar Valley, Yellowstone National Park, Wyoming. There's around 3,700 bison the park, of the Plains Bison subspecies.
Yellowstone may be the only place where bison have not been hunted out of existence, although the population plummeted due to poaching at the turn of the 20th century. The population is still under threat - when they roam outside the park boundaries, and from claims that they transmit disease such as brucellosis to cattle.