Pronghorn antelope

Pronghorn antelope near Yellowstone National Park.

Bighorn ram

Bighorn ram in Yellowstone National Park.

Bighorn ram

Bighorn ram in Yellowstone National Park.

Bighorn ram

Bighorn ram in Yellowstone National Park.

Bighorn ram showing signs of sore mouth disease

Bighorn ram showing signs of sore mouth disease in Yellowstone National Park

Bighorn ram in front of the Beartooth Mountains

Bighorn ram in front of the Beartooth Mountains in Yellowstone National Park

Bighorn ram and a lamb during rut

Bighorn ram and a lamb during rut in Yellowstone National Park

Bighorn ram scenting the air

Bighorn ram scenting the air during the rut in Yellowstone National Park.

Bighorn ram scenting the air

Bighorn ram scenting the air during the rut in Yellowstone National Park.

Bighorn rams

Bighorn rams in Yellowstone National Park.

Bighorn ram in the sun.

Bighorn ram in the sun in Yellowstone National Park.

Bighorn rams

Bighorn rams in Yellowstone National Park.

Bighorn ram showing signs of sore mouth disease

Bighorn ram showin signs of sore mouth disease in Yellowstone National Park.

Bighorn ram soaking up the winter sun

Bighorn ram soaking up the winter sun in Yellowstone National Park.

Closeup of bighorn sheep

Closeup of bighorn sheep grazing in Yellowstone National Park.

Bull bison

Bull bison sitting by the Firehole River in Yellowstone National Park.

Coyote in the snow

Coyote hunting in the snow in Yellowstone National Park.

Coyote hunting

Coyote hunting in a field in Yellowstone National Park.

Bull elk grazing

Bull elk grazing as the snow falls in Yellowstone National Park, Wyoming

Coyote

Coyote giving me a look through the falling snow in Yellowstone National Park, Wyoming

Coyote

Coyote in the snow in Yellowstone National Park, Wyoming

Sunset at Great Fountain Geyser

Sunset at Great Fountain Geyser in Yellowstone National Park, Wyoming

Bubbling mudpot

A bubbling mudpot in Yellowstone National Park, Wyoming

Bacterial Mat at Grand Prismatic Hot Spring

Bacterial Mat at Grand Prismatic Hot Spring in Yellowstone National Park, Wyoming

Bacterial Mat at Grand Prismatic Hot Spring

Bacterial Mat at Grand Prismatic Hot Spring in Yellowstone National Park, Wyoming

Hot Spring

Unnamed hot spring at Biscuit Basin in Yellowstone National Park, Wyoming

Jewel Geyser

Jewel Geyser erupting in Yellowstone National Park, Wyoming

Sapphire Pool

Sapphire Pool in Yellowstone National Park, Wyoming

Black Opal Pool

Black Opal Pool and the Firehole River in Yellowstone National Park, Wyoming

Opalescent Pool

Opalescent Pool in Yellowstone National Park, Wyoming.

Old Faithful Geyser

A fall eruption of Old Faithful Geyser in Yellowstone National Park, Wyoming

Grand Prismatic Hot Spring

Grand Prismatic Hot Spring in Yellowstone National Park, Wyoming

Panorama of Grand Prismatic Hot Spring

Panorama of Grand Prismatic Hot Spring in Yellowstone National Park, Wyoming

Bison on Soda Butte Creek

Bison on Soda Butte Creek with The Thunderer in the background, Yellowstone National Park, Wyoming.

Detail of Grand Prismatic Hot Spring

Detail of Grand Prismatic Hot Spring in Yellowstone National Park, Wyoming