Mark MacEwen / Elk (Cervus canadensis) stag resting outside house during the rut, Estes Park, Larimer County, Rocky Mountains, Colorado, United States, September.

George Sanker / Elk (Cervus elaphus canadensis) bull walking in grassland at dusk. Yellowstone National Park, Wyoming, USA. September.

Sebastian Kennerknecht / American Elk (Cervus elaphus nelsoni) bull grazing in winter, Gardiner, Yellowstone National Park, Montana

Phil Savoie / Elk (Cervus canadensis) female with suckling calf, Yellowstone National Park, Montana, USA. July.

Phil Savoie / Elk (Cervus canadensis) female and calf, Yellowstone National Park, Montana, USA. July.

Phil Savoie / Elk (Cervus canadensis) cow, Yellowstone National Park, Montana, USA, July.

Phil Savoie / Elk (Cervus canadensis) young calf, Yellowstone National Park, Montana, USA, July.

Charlie Summers / Two young bull Elk (Cervus canadensis) practicing rutting, Rocky Mountain National Park, Colorado, USA, October.

Jeff Foott / Elk (Cervus elaphus canadensis) and dead trees killed by Mountain pine beetle infestation (Dendroctonus ponderosae), Rocky Mountain National Park, Colorado, USA. September. The current outbreak of mou...

George Sanker / Elk (Cervus canadensis) silhouetted against gloomy sky, Yellowstone National Park, Wyoming, USA, June.

George Sanker / Elk (Cervus canadensis) silhouetted against grey sky, Yellowstone National Park, Wyoming, USA, June.

Sylvain Cordier / Elk or Wapiti (Cervus canadensis), walking on a hill, Yellowstone National Park, USA