Juergen & Christine Sohns / Mountain Zebra (Equus zebra), Mountain Zebra National Park, South Africa

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

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

Jack Dykinga / Gaucho herding horses on the shoreline of Lago Almarga in the morning light, with Torres del Paine mountains in background under stormy skies. Patagonia, Chile.

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

Richard Du Toit / Burchell's Zebra (Equus burchellii) trio nuzzling, Itala Game Reserve, South Africa

Yva Momatiuk & John Eastcott / Mustang (Equus caballus) mother and foal, Oshoto, Wyoming

Yva Momatiuk & John Eastcott / Mustang (Equus caballus) mother and foal, Oshoto, Wyoming

Phil Savoie / Point-to-Point horse racing, low angle view of racehorses jumping fence, Monmouthshire, Wales, UK. March 2014.

Phil Savoie / Point-to-Point horse racing, low angle view of racehorses jumping fence, Monmouthshire, Wales, UK. March 2014.

Phil Savoie / Point-to-Point horse racing, low angle view of racehorse jumping fence, Monmouthshire, Wales, UK. March 2014.

Cyril Ruoso / Feral Horses (Equus caballus) gathering around waterhole, Namib-Naukluft National Park, Namibia.