The last surviving subspecies of undomesticated horse, extinct in the wild for nearly 50 years, is making a slow recovery in Mongolia.

The comeback of the Przewalski—regarded as the last of the truly wild horse species—is due largely to the dogged determination of Claudia Feh. For the past quarter-century, the Swiss environmentalist has led efforts to reestablish Przewalskis on the Mongolian steppe, where they once thrived.

The Przewalski (pronounced shuh-Val-skee) has been around for more than 100,000 years. But the squat, stubby-legged horse was little known outside of Eurasia until the 15th century and wasn't widely known by its current name until it was popularized in the 1880s by Russian explorer Nikolai Przhevalsky.

Too wild to be domesticated—in captivity, Przewalski stallions were