Mountain Hare

The mountain hare is adapted to cold polar and mountain habitats. It is generally smaller than the European hare and has a tail that remains completely white throughout the year. Most populations are brown in summer and white or grey in winter, providing seasonal camouflage; coat timing varies with climate and locality. The year-round white tail is the clearest distinction from the brown hare. (Wikipedia, general species account)

Its Palearctic habitats include tundra, forest, and mountain moorland, with high densities often occurring where sheltered cover meets open feeding ground. In winter animals move toward more protected sites. The diet shifts with local vegetation but consists of plant matter such as grasses, twigs, and bark. Mongolia is within the documented native range, though the opened sources named no local viewing site. (Animal Diversity Web; Wikipedia, general species account)