Roland Seitre / Tibetan wild ass (Equus kiang) in snow. Captive at Moscow Zoo breeding station. Occurs on the Tibetan plateau..

Kristel Richard / Wild Mongolian mare and her foal trotting, plains at the foot of Dungurukh Uul mountain, near the border with China and Kazakhstan, Bayan-Olgiy aymag, Mongolia. September.

Terry Whittaker / Bay Icelandic horse trotting in the snow, Snaefellsnes Peninsula, Iceland, March.

Kristel Richard / A herd of Retuerta mares trotting, Guadiamar scientific reserve, Donana National Park, Andalusia, Spain. This breed of horse was close to extinction in the 1990s with only 5 individuals left, but now...

Carol Walker / Lusitano horse, grey stallion trotting, Portugal

Carol Walker / Lusitano horse, grey stallion trotting, Portugal

Kristel Richard / A purebred Lusitano colt (with his mane and tail cut to mark his first year) trotting in the arena at the Companhia das Lezírias Stud Farm, Samora Correia, Santarém, Portugal, July 2011

Carol Walker / Grey Andalusian / Spanish stallion running, California, USA

Sergey Gorshkov / Aerial view of Caribou / Reindeer (Rangifer tarandus) trotting through shallow water, Kamchatka, Far east Russia, August

Charlie Summers / Mustang (Equus caballus) herd trotting in light snow covered prairie, IRAM Wild Horse Sanctuary south of Hot Springs, South Dakota, USA, May

Kristel Richard / A Khampa warrior leads his Tibetan horse towards the start of the race, during the horse festival, near Huangyan, in the Garze Tibetan Autonomous Prefecture in the Sichuan Province, China, June 2010

Laurent Geslin / Group of Wild Boar (Sus Scrofa) trotting through forest of Rambouillet, near Paris, France. Autumn.