Cyril Ruoso / Przewalski's Horse (Equus ferus przewalskii) herd, Gobi Desert, Mongolia

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.

Enrique Lopez-Tapia / Kiangs (Equus kiang) on grassland near Tso Kar Lake, Chantang Wildlife Sanctuary. Ladakh, India, September 2018.

Richard Du Toit / Red-billed Oxpecker (Buphagus erythrorhynchus) on Burchell's Zebra (Equus burchellii), Mkhuze Game Reserve, KwaZulu-Natal, South Africa

Andrew Peacock / White Rhinoceros (Ceratotherium simum) mother and calf in grassland, Ol Pejeta Conservancy, Kenya

Sebastian Kennerknecht / South African Giraffe (Giraffa giraffa giraffa) juvenile at sunset, Greater Makalali Private Game Reserve, South Africa

Sebastian Kennerknecht / American Bison (Bison bison) herd grazing in winter, Gardiner, Yellowstone National Park, Montana

Sebastian Kennerknecht / American Bison (Bison bison) herd grazing in winter, Gardiner, Yellowstone National Park, Montana

Sebastian Kennerknecht / American Bison (Bison bison) bull browsing in winter, Yellowstone National Park, Wyoming

Sebastian Kennerknecht / American Bison (Bison bison) female cleaning nose with tongue, Yellowstone National Park, Wyoming

Sebastian Kennerknecht / American Bison (Bison bison) female in winter, Yellowstone National Park, Wyoming

Sebastian Kennerknecht / American Bison (Bison bison) female covered with frost in winter, Yellowstone National Park, Montana