Yaks have a bulky frame and cloven hooves. Their long hairy coat is coloured dark black to brown. This long coat helps to insulate them in their cold environment. In some yaks their hair reaches the ground. On their chest, flanks and thighs they have a dense woolly undercoat.
They have horns which come out from the side of the head and curve forward in males. These can be from 48-99cm (19-39in) long. Females have smaller horns which go upright. These measure only 27-64cm (11-25in) long.
Over the back of the shoulders is a hump. In males this is more pronounced.
Wild male yaks stand 1.6-2.2m (5.2-7.2ft) tall at the shoulder and measure 2.5-3.3m (8.2-11ft) from the head to the base of the tail. The tail is 60-100cm (24-39in) long. Weights vary between 305 and 1000kg (672-2,205lb). Females are one third the weight and 30% as long as males. Domesticated yaks are also smaller with males weighing 350-580kg (770-1,280lb). Females are still smaller at between 225 and 255kg (496 and 562lb).
Yaks are herbivores. Their diet consists mainly of grasses and sedges. Some herbs, winterfat shrub, mosses and lichens are also consumed.
Their horns are used to break through the snow and reach the plants. Once consumed their food passes through numerous stomachs so they can get all of the nutrients out of their food.
Asia is the native home of the yak. Wild populations are found throughout Tibet, China, and India. In the past they were found in Nepal and Bhutan but they are now extinct in these areas.
Yaks make their homes in treeless areas which are on mountains and plateaus. A lot of the time they live in alpine meadows.
Mating takes place between July and September when it is warmest in these areas.
As the breeding season approaches males begin to fight to see who will be dominant. They will bellow and scrape the ground with their horns as well as charging each other with their horns. They scent mark with urine and dung and wallow in dry soil. Females are able to mate up to four times over the mating period but only for a few hours at each chance.
After nine months a single calf is born. A secluded spot is found for the birth. After 10 minutes the calf is walking and can join the herd. It takes one year for the calf to wean and become independent. They begin life brown in colour and this fur slowly darkens to match that of the adults.
At around 3-4 years of age females are sexually mature. They will give birth every second year unless food is plentiful in which case they may breed yearly.
Predators of the yak included Tibetan wolves, brown bears and snow leopards. The last two are more likely to take young and sick individuals.
Yaks live in herds of several hundred individuals. These are formed mostly of females and young with the occasional male. Most males live in bachelor herds or are solitary.
The only vocalisation made by the yak is a grunt. They do not moo like other cows.
Yaks are part of the same family as bison and domestic cattle.
The yaks scientific names translate to grunting bull (bos grunniens) and silent bull (bos mutus).
In Asia yak racing is a sport as is yak skiing and yak polo.
Yaks are used in Asia for transport and the production of meat, wool and milk.
By travelwayoflife (Flickr) [CC BY-SA 2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons
By Pongratz (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons
Buzzard, P. & Berger, J. 2016. Bos mutus. The IUCN Red List of Threatened Species 2016: e.T2892A101293528. https://dx.doi.org/10.2305/IUCN.UK.2016-2.RLTS.T2892A101293528.en. Downloaded on 01 May 2020.
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