Don’t jump to conclusion –that yak you see carrying a load for a trekking party is probably a crossbreed called a zopkyo. A true yak is a handsome long haired, wide – horned bull of the boss grannies species, and his female counterpart is a nak . Cross a yak or a nark with a Nepalese cow or bull and you’ll have an infertile zopkyo male or a dzum if a female is produced? Not usually found below about 3500m (1148ft) the true domestic yak is a multipurpose beast , used out and woven into blankets or ropes , and its dung is an important source of fuel . Milk from the nak and dzum is used to make butter or cheese (never ask for yak cheese) while the moderately docile zopkyo is mostly a beast of burden.