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

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

David Pattyn / Alpine ibex (Capra ibex) adult males fighting in alpine landscape, Valsavarenche, Gran Paradiso National Park, Aosta Valley, Italy, May

David Pattyn / Alpine Ibex (Capra ibex) in its landscape, Valsavarenche, Gran Paradiso national park, Aosta Valley, Italy, May

David Pattyn / Alpine ibex (Capra ibex) struggling in deep snow on a steep slope, Valsavarenche, Gran Paradiso National Park, Aosta Valley, Italy, January

Eric Baccega / Female Uganda kob (Kobus kob thomasi) suckling calf. Murchisson Falls National Park, Uganda. February.

Jed Weingarten / Wild Wonders of China / Takin (Budorcas taxicolor) Tangjiahe Nature Reserve, Sichuan Province, China. April.

Jed Weingarten / Wild Wonders of China / Snow leopard (Uncia uncia) with Bharal (Pseudois nayaur) prey, Serxu County, Garze Prefecture, Sichuan Province, China.

Anup Shah / Mixed herd of Common or Plains zebra (Equus quagga burchellii) and Eastern white-bearded wildebeest (Connochaetes taurinus) - remote camera. Masai Mara National Reserve, Kenya.

Donald M. Jones / Bighorn Sheep (Ovis canadensis) ram, Montana

Donald M. Jones / Bighorn Sheep (Ovis canadensis) ram, Montana

Donald M. Jones / Bighorn Sheep (Ovis canadensis) female and male in winter, Jasper National Park, Alberta, Canada