In Romanised Tibetan, "a" is pronounced roughly the same as the start of "about" or the "u" in "hut" rather than the "a" in "hat"? That doesn't make "Yak" quite "Yuk", since in Lhasa dialect, a word-final "k"/"g" is phonetically unreleased (or even glottalised or omitted) but it's close enough. "Unreleased" means that you cut-off the "k" as soon as you reach it; if you want to try making an unreleased word-final "k" yourself, try making a "bk bk bk" chicken sound. But I digress.
How a maid can milk a bull / And every stroke a bucketful." ("Willow's Song", Paul Giovanni)
Properly speaking, even though in common English usage "yak" is gender-neutral, in Tibetan yaks are only male; a female is either a "dri" or "nak". I'll continue, however, to improperly use "yak" only.
During warmer months, nomads herd their yaks and longhorned sheep out on the grasslands of the Tibetan Plateau. Yaks are central to the traditional Tibetan way of life. Their standard tents are made of black yak hair and filled with the smoke from burning yak dung, which gives them lung and eye diseases; their festival tents are white and decorated with floral designs. When the cold approaches, they retreat with their herds to their permanent winter homes; in one such home, we stayed.
The winter home, a cosy two-room cottage, was kept year-round by a 67 year-old grandmother. The unheated entrance room was used mainly as a storeroom (though half of our group needed to sleep there); the living room was kept warm by a yak-dung stove, which was thankfully vented through a chimney. You see hand-pressed dung drying on (vertically) walls all over. We had vegetarian thenthuk (a tasty flat-noodle stew), and tsampa (a not-so-tasty mix of yak butter, tea or water, roasted barley flour, yak cheese, and sugar; somewhat resembling cheesecake base and probably nicer if baked).
Yak cheese comes granulated, is extremely tough to chew, and is unmemorable in taste; it's unsuitable for making cheesecake. Yak yoghurt is strongly recommended if (like me) you prefer yours natural-style, and often arrives over chunks of fruit. Though yak-milk yoghurt is very pleasant, yak milk is strong tasting. It cuts through the sugar and spice of Masala tea, and yak butter is even stronger. I tried yak butter tea -- a Tibetan staple -- for the first (and probably last) time in Samye. The original reason for using yak butter instead of milk is probably that it could be stored for longer: nomads lack refrigeration, and summer on the grasslands can be warm.
Every temple is filled with yak-butter lamps, often large and multi-wicked, and many worshippers bear either bottles and jugs full of melted butter, containers of solid butter, or else small yak-butter lamps in order to keep the fuel topped up. Tibetan temples' air is heavy with the scent of burning butter, and their surfaces are coated with years-worth of burnt butter residue and congealed spillage. Sacred sculptures are made with a mixture of yak butter, barley flour, and dyes. They last while the weather is cool; when it warms they slowly melt and rancidify. These sculptures are constructed with great skill, and the butter gives them a slight translucence, making flesh and petals seem more lifelike - much as wax or marzipan is used elsewhere.
On the flat, shorter-haired dzo, a crossbred yak-cow hybrid, are more common (the backstreets of Gyangtse are filled with them), but on the high slopes, where the footing is precarious and snows can accumulate, yaks appear frequently and dzo do not. At the snowy pass overlooking the holy lake of Yamdrok Tso, groomed and saddled yaks were available for photo opportunities.
Yaks are covered with shaggy fur, normally black but sometimes white. Rough-spun yak-hair cloth, much like hessian, is used for tents and as temple shades on which are displayed Tibetan Buddhism's eight auspicious symbols. Softer wool can also be produced and turned into yarn or cloth. Their fur is wrapped around temple prayer poles, or dyed red to make decorative ruffs for Tibetan mastiffs and livestock or tassels for work animals. Their meat, apparently a touch gamey in taste, is a staple part of the Tibetan diet, and their leather, horns, and bones are all used in craftwork.