As the weather becomes colder and the snow deeper, Bison move towards the hot springs and geothermal area's. The Madison river receives warmth from the geysers and so keeps the snow at bay. It is not so deep so the bison can feed on what little substance there is in the grasses. Here a herd of Bison along the banks of this river.
Location: Madison River, Yellowstone, Wyoming, USA
Photographer: Ron Tear