Abstract
Within the sheep discrimination systems adopted by Mongolia nomads, the age determination method by teeth observation was especially studied. Nomads have discriminated their own individual sheep according to their experience, and at the same time, determined the age and sex of individual sheep by means of the appearance. Beside, when discriminating individual sheep, nomads sometimes have determined the age of the sheep by observing the teeth. The age determination method of sheep adopted by nomads has been that by observing incisors of the lower jaw. The results of age determination method of sheep by teeth observation adopted by West Mongolian nomads agreed with those of the method adopted in Japan for all ages except for the age of the third and fourth calendar year.
