Przewalski's horse

Przewalski's horse ("Equus przewalskii" or "E. ferus przewalskii"), the Mongolian wild horse, is a close relative of the domestic horse. The two are the only equids that can cross-breed and produce fertile offspring. Przewalski's horse is a rare and endangered subspecies of the wild horse, "Equus ferus". It is native to the steppes of central Asia, especially Mongolia.
At one time extinct in the wild, it has been reintroduced to its native habitat in Mongolia from stock in zoos. It is now in several nature reserves and national parks. As of 2002, the world population of these horses was about 1,000.
Relationships between horses.
Most "wild" horses today, such as the American mustang or the Australian brumby, are feral horses descended from domesticated animals which escaped and adapted to life in the wild. In contrast, Przewalski's horse has never been successfully domesticated, and remains a truly wild animal today.
Przewalski's horse is one of three known subspecies of "Equus ferus", the others being the domesticated horse, "Equus ferus caballus" and the extinct tarpan, "Equus ferus ferus". Przewalski's horse is the only remaining truly wild "horse" in the world. There are still a number of other wild equines, including three species of zebra and various subspecies of the African wild ass, onager (including the Mongolian wild ass) and kiang.
Relation to domestic horse.
Although Przewalski's horse can hybridize with domestic horses to produce fertile offspring, it has an extra pair of chromosomes.
In zoos.
According to ISIS, about 480 Przewalski's were reported in captivity.