Mark Higgins, age 13, of Chattanooga, Tenn., for his question:

HOW BIG IS THE YAK?

The yak is a wild or domesticated Tibetan ox. It is native to the high plateaus and mountains of Central Asia where the climate is cold and dry.

The wild yak is a massive animal that is blanketed with a thick coat of grayish brown long hair. The bulls, which are larger than the females, are about six feet high at the shoulder and weigh more than 1,000 pounds. The back of the yak is humped at the shoulders. The yak has long horns that spread outward and upward. The tail is long haired and bushy.

The domestic yak is of various colors, chiefly black and white, and of smaller size than the wild animal, as a reuslt of crossbreeding with cattle.

Yaks are valuable as beasts of burden. Their milk is rich and yields excellent butter and curd. The flesh, eaten either roasted or dried, is of high quality.

The hair of the domestic yak is spun into rope and woven into cloth. The hide is used for leather.

The yak utters a low, gutteral sound instead of lowing like an ox. Because of this, the animal is sometimes called a grunting cow or grunting ox.