Few, if any, of the yak that travelers see are wild yak or drong. Most in fact are not even yak at all but rather dzo, a cross between a yak and a bull. A domestic yak rarely exceeds 1.5m in height and unlike its wild relative, it varies in shades of black to grey and, primarily around Kokonor in Qinghai, white. To see only one of a certain colour of yak in a herd is considered a bad omen, while two or more are considered a sign of luck.

       Despite their massive size, yak are surprisingly sure-footed and graceful on steep, narrow trails, while burdened by loads of up to 70kg. Yak panic easily and will struggle to stay close together. This gregarious instinct allows herders to drive packs of animals through snow-blocked passes, thus creating a natural snowplow.

        Most impressive is the yak's ability to sustain high altitudes. In fact, a descent below 3000m may impair the reproductive cycle and even expose yak to parasites and disease. Cloaked in layers of shaggy, coarse hair and blanketed by a soft undercoat, yak use their square tongues and broad muzzles to forage close to the soil in temperatures that frequently drop to -40"C. With three times more red blood cells than the average cow, yaks thrive in the oxygen-depleted high altitudes. Their curious lung formation, consisting of 14 or 15 pairs of ribs rather than the 13 typical of cattle, allows a large capacity of inhaling and expelling air", thus the Latin name Bos grunniens, or the grunting ox.

       For centuries the Tibetan nomads have valued the yak. Legends suggest that Guru Rinpoche domesticated the first yak. Tibetans rely on yak milk for cheese, as well as butter for the ubiquitous butter tea and offerings to butter lamps in monasteries. Yak hair is woven into rope and tails are used in both Buddhist and Hindu religious practices. Yak tail hair was the main material used to produce Father Christmas beards in 1950s America! Wool is spun into chara felt and used to make bags, blankets and tents. Yak hide is used for the soles of boots and the yak heart is used in Tibetan medicine. Rare, hornless yak are in demand for riding. In the nomadic tradition, no part of the animal is wasted and even yak dung is required as a fundamental fuel, left to dry in little cakes on the walls of most Tibetan houses. Yak are generically referred to as Nor, meaning wealth, therefore a man's worth is measured by the size of his herd. So important is the yak to the Tibetans that, like their children, each yak is named.

         Just as the yak are instrumental in the continuing salt-grain trade of the nomads, herders take great care to ensure the health and safety of the animals. Relocation three to eight times a year provides adequate grazing. Every spring the thick yak coats are carefully trimmed. Nomads rely on unique veterinarian skills, which they use to lance abscess, set broken bounds and sear cuts. For some wounds a technique of wrapping in felt and keeping moist via human urine may be used.

        Of the 14 million domesticated yak worldwide, five million reside on the Qinghai-Tibetan plateau. The yak, with its extraordinary composition and might, has perhaps been the sole instrument in rendering possible the harsh life of Tibet's nomads, or drokpa, and the two coexist in admirable harmony.