Igor Shpilenok / European Bison (Bison bonasus) calf and mother portrait. 'Mefody', first calf born to reintroduced herd in Bryansk Forest. Bryansk Forest Zapovednik, Kamchatka, Russian Far East, May.

Denis-Huot / African buffalo (Syncerus caffer) male covered with mud after mud bathing, Nakuru National Park, Kenya

Denis-Huot / African buffalo (Syncerus caffer) herd drinking in front of Voi lodge, aerial view, Tsavo East National Park, Kenya

Denis-Huot / African Buffalo (Syncerus caffer) males fighting, Nakuru National park, Kenya

George Sanker / American Buffalo / Bison (Bison bison) grazing in open plains. Yellowstone National Park, Wyoming, October.

Christophe Courteau / African Buffalo {Sincerus caffer} bull taking a mud bath, Okavango Delta, Botswana.

Christophe Courteau / Two African Buffalo {Sincerus caffer} bulls sparring, Okavango Delta, Botswana.

Anup Shah / Forest buffalo (Syncerus caffer nanus) standing and urinating in a river running through Bai Hokou, Dzanga Sangha Special Dense Forest Reserve, Central African Republic. December 2011.

Danny Green / Bison (Bison bison) seen through blizzard snow. Yellowstone National Park, USA, February.

Danny Green / Bison (Bison bison) in snow. Yellowstone National Park, USA, February.

Danny Green / Bison (Bison bison) in snowstorm. Yellowstone National Park, USA, February.

Danny Green / Bison (Bison bison) in snowstorm. Yellowstone National Park, USA, February.