Koulan

1. A wild horse (Equus onager or Asinus onager) inhabiting the plains of Central Asia; -- called also gour, khur, and onager.
   

It is sometimes confounded with the dziggetai, to which it is closely related. It is gray in winter, but fulvous in summer. It has a well defined, dark, dorsal stripe, and a short, erect mane. In size, it is intermediate between the horse and ass.