For the movement of their animals, the herders depend on the vast native grasslands between altitudes of 2,600 to 5,000 m. to feed their animals. Yak production in these areas and especially above the tree line (4,000 m.) is recognized as the only viable enterprise where the high altitude grasslands are efficiently converted into sources of energy for human use at no opportunity cost (Gyamtsho, 1996; Ura, 1993). In the summers the herders take their animals to pastures as high as 5,000 m. and come down in the winters to 2,600. Herders respect and follow their age-old traditional migratory routes to respective designated pastures in the various elevations for which they have traditionally grazing rights.