Daniel J. Cox / Gray Wolf (Canis lupus) pair predating female Elk (Cervus elaphus) crossing river, Alum Creek, Yellowstone National Park, Wyoming, sequence 1 of 4

Tim Fitzharris / Grand Tetons from Schwabacher Landing, Grand Teton National Park, Wyoming

Tim Fitzharris / Conifers and Lower Yellowstone Falls, Yellowstone River, Grand Canyon of Yellowstone, Yellowstone National Park, Wyoming

Sebastian Kennerknecht / American Bison (Bison bison) bull browsing in winter, Yellowstone National Park, Wyoming

Sebastian Kennerknecht / American Bison (Bison bison) female cleaning nose with tongue, Yellowstone National Park, Wyoming

Sebastian Kennerknecht / American Bison (Bison bison) female in winter, Yellowstone National Park, Wyoming

Daniel J. Cox / Gray Wolf (Canis lupus) pack on ridge in winter, Lamar Valley, Yellowstone National Park, Wyoming

Yva Momatiuk & John Eastcott / Mustang (Equus caballus) mother and foal, Oshoto, Wyoming

Yva Momatiuk & John Eastcott / Mustang (Equus caballus) mother and foal, Oshoto, Wyoming

Jim Manthorpe / American bison (Bison bison) feeding, Yellowstone National Park, Wyoming, USA, August.

Radomir Jakubowski / Red fox (Vulpes vulpes) face portrait in snow, Grand Teton National Park, Wyoming, USA, February.

Radomir Jakubowski / Red fox (Vulpes vulpes) in snowfall, Grand Teton National Park, Wyoming, USA, February.