Jeff Foott / Pronghorn Antelope (Antilocapra americana) male in grassland, Wind Cave National Park, South Dakota

Sebastian Kennerknecht / American Bison (Bison bison) herd grazing in winter, Gardiner, Yellowstone National Park, Montana

Sebastian Kennerknecht / American Bison (Bison bison) herd grazing in winter, Gardiner, Yellowstone National Park, Montana

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

Sean Crane / American Bison (Bison bison) mother and calf at sunrise, Yellowstone National Park, Wyoming

Tim Laman / Adult male Bornean orangutan (Pongo pygmaeus) in rainforest canopy, Gunung Palung National Park, Borneo, West Kalimantan, Indonesia

Suzi Eszterhas / American Bison (Bison bison) cow and calf playing, Yellowstone National Park, Montana

Shin Yoshino / American Bison (Bison bison) two males fighting, Yellowstone National Park, Wyoming

Ralf Kistowski/ BIA / Coyote (Canis latrans) in winter, Yellowstone National Park, Wyoming

Jeff Foott / Black-tailed Prairie Dog (Cynomys ludovicianus) in burrow, Wind Cave National Park, South Dakota

Jeff Foott / Black-tailed Prairie Dog (Cynomys ludovicianus), Wind Cave National Park, South Dakota

Jeff Foott / Black-tailed Prairie Dog (Cynomys ludovicianus) in territorial display, Wind Cave National Park, South Dakota