An Arabian bay horse. Most modern horses, with the exception of the truly wild Przewalski's Horse, are either domesticated or feral descendants of once-domestic horses.
The Przewalski's Horse (Equus ferus) is a success story, improving its status from critically endangered to endangered. Originally, it was listed as "Extinct in the Wild" in 1996, but thanks to a captive breeding program and a successful reintroduction program, the population is now estimated at more than 300, according to the IUCN.
The iconic Clydesdale adds catchet to the Budweiser beer brand.
Midnite the miniature horse was born without one of his back legs. Abused by his owners, the tiny pony was rescued by law officials and given to volunteers at a charity ranch in Fort Worth, Texas. He was just weeks away from being put down when a local prosthetics company — that usually makes prosthetic devices for humans — agreed to make Midnite a new leg. After the fitting, the 4-year-old horse was able to gallop for the first time in his life.
A group of wild horses (descended from domestic stock) on the beach on Assateague Island, Maryland.
An illustration of the earliest-known horse Sifrhippus, dwarfed next to a modern domestic horse.
Two male mustangs vie for breeding rights.
An appaloosa, known for its spotted coat, runs through the snow. (This photo corrects a previous version.)