Along the Firehole river, a lone bison feeds on grasses kept from snow by thermal activity found in the geyser basins of Yellowstone National Park. Yellowstone was home to the last, wild, free-roaming bison at the turn of the 19th century. In less than one hundred years, wholesale slaughter reduced the number of bison from an estimated high of sixty million to under three thousand animals. These remaining bison found refuge in Yellowstone National Park. Now thousands of these animals roam the Yellowstone ecosystem.