Donald M. Jones / Elk (Cervus elaphus) bull bugling, Alberta, Canada

Mark Raycroft / Elk (Cervus elaphus) bull in river in mist, North America

Mark Raycroft / Elk (Cervus elaphus) bulls fighting, North America

Donald M. Jones / Elk (Cervus elaphus) bulls fighting, western Canada

Donald M. Jones / Elk (Cervus elaphus) bull bugling, western Canada

Danny Green / Moose Bull (Alces alces) walking in forest clearing, Denali National Park, USA, September

George Sanker / Moose (Alces alces) bull swimming in water, Baxter State Park, Maine, USA.

Jeff Vanuga / Shiras moose (Alces alces shirasi) bull in rut. Grand Teton National Park, Wyoming, USA, October.

Jeff Vanuga / Elk (Cervus canadensis) bull in velvet silhouetted against a setting sun, Yellowstone National Park, Wyoming, USA, May.

Donald M. Jones / Elk (Cervus elaphus) bull rubbing tree during rut, western Canada

Donald M. Jones / Elk (Cervus elaphus) bull flehming, western Canada

Donald M. Jones / Elk (Cervus elaphus) bull bugling, western Canada