Danny Green / Reindeer (Rangifer tarandus), two play fighting in snow. Svalbard, Norway, April.

Nick Garbutt / American bison (Bison bison) female covered in hoar frost near hot spring, portrait. Midway Geyser Basin, Yellowstone National Park, USA. February.

Staffan Widstrand / Southern Giraffe (Giraffa camelopardalis) two, with one in foreground, Zimanga Private Nature Reserve, KwaZulu Natal, South Africa

Oscar Dewhurst / Fallow deer (Dama dama) walking across frost-covered playing fields at dawn, with tower blocks of London in the background. Richmond Park, London, UK. December

Oscar Dewhurst / Red deer (Cervus elaphus) stag roaring, silhouetted under trees at sunrise. Bushy Park, London, UK. September

Jack Dykinga / Bighorm sheep (Ovis canadensis) males grouped together before the rutting season. Valley of Fire State Park, Nevada, USA, February.

Stephane Granzotto / Alpine ibex (Capra ibex) feeding in deep snow, digging to reach food, Rhone-Alpes, France, December.

Danny Green / Bison (Bison bison) herd walking in line in snow, Yellowstone National Park, Wyoming, USA, February

Inaki Relanzon / Arabian Oryx (Oryx leucoryx) at sunset. Previously extinct in the wild, their conservation status is now stable thanks to conservation efforts.This male is part of a reintroduction program in Dubai, U...

Ann & Steve Toon / Cape buffalo (Syncerus caffer) at waterhole at night with plains zebra (Equus quagga), Zimanga private game reserve, KwaZulu-Natal, South Africa, September

Ann & Steve Toon / Cape buffalo (Syncerus caffer) drinking at waterhole at night, Zimanga private game reserve, KwaZulu-Natal, South Africa, September

Nick Garbutt / Herd of American bison (Bison bison) in snow, Yellowstone National Park, Wyoming, Yellowstone, January.