The
yak,
Bos grunniens or
Bos mutus, is a long-haired bovine found throughout the Himalayan region of south
Central AsiaCentral Asia is a core region of the Asian continent from the Caspian Sea in the west, China in the east, Afghanistan in the south, and Russia in the north...
, the
Tibetan PlateauThe Tibetan Plateau , also known as the Qinghai–Tibetan Plateau is a vast, elevated plateau in Central Asia covering most of the Tibet Autonomous Region and Qinghai, in addition to smaller portions of western Sichuan, southwestern Gansu, and northern Yunnan in Western China and Ladakh in...
and as far north as
MongoliaMongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
and
RussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. In addition to a large domestic population, there is a small, vulnerable wild yak population. In the 1990s, a concerted effort was undertaken to help save the wild yak population.
Etymology
The
EnglishEnglish is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
word "yak" derives from the
TibetanThe Tibetan languages are a cluster of mutually-unintelligible Tibeto-Burman languages spoken primarily by Tibetan peoples who live across a wide area of eastern Central Asia bordering the Indian subcontinent, including the Tibetan Plateau and the northern Indian subcontinent in Baltistan, Ladakh,...
, or
gyag – in Tibetan this refers only to the male of the species, the female being called a
dri or
nak. In English, as in most other languages which have borrowed the word, "yak" is usually used for both sexes.
Taxonomy
Yaks belong to the genus
BosBos is the genus of wild and domestic cattle. Bos can be divided into four subgenera: Bos, Bibos, Novibos, and Poephagus, but these divisions are controversial. The genus has five extant species...
, and are therefore closely related to
cattleCattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
(
Bos primigenius).
Mitochondrial DNAMitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
analyses to determine the evolutionary history of yaks have been somewhat ambiguous. There is little differentiation between a Yak and the Highland Cattle. The yak may have diverged from cattle at any point between one and five million years ago, and there is some suggestion that it may be more closely related to
bisonMembers of the genus Bison are large, even-toed ungulates within the subfamily Bovinae. Two extant and four extinct species are recognized...
than to the other members of its designated genus. Apparent close fossil relatives of the yak, such as
Bos baikalensis, have been found in eastern Russia, suggesting a possible route by which yak-like ancestors of the modern
American bisonThe American bison , also commonly known as the American buffalo, is a North American species of bison that once roamed the grasslands of North America in massive herds...
could have entered the Americas.
The species was originally designated as
Bos grunniens ("grunting ox") by
LinnaeusCarl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...
in 1766, but this name is now generally only considered to refer to the domesticated form of the animal, with
Bos mutus ("mute ox") being the preferred name for the wild species. Although some authors still consider the wild yak to be a
subspeciesSubspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
,
Bos grunniens mutus, the
ICZNThe International Commission on Zoological Nomenclature is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 28 members from 20 countries, mainly practicing zoological taxonomists...
made an official ruling in 2003 permitting the use of the name
Bos mutus for wild yaks, and this is now the more common usage.
Except where the wild yak is considered as a subspecies of
Bos grunniens, there are no recognised subspecies of yak.
Physical characteristics
Wild yaks are among the largest bovids, with adults standing about 1.6 to 2.2 m (5.2 to 7.2 ft) tall at the shoulder and weighing 325–1000 kg (716.5–2,204.6 lb) and having a head and body length of 2.5 to 3.4 m (8.2 to 11.2 ft). The tail is 70 to 100 cm (27.6 to 39.4 in) long in wild yaks. The females weigh about one third of this and are about 30% smaller in their linear dimensions.
DomesticatedDomestication or taming is the process whereby a population of animals or plants, through a process of selection, becomes accustomed to human provision and control. In the Convention on Biological Diversity a domesticated species is defined as a 'species in which the evolutionary process has been...
yaks are much smaller, males weighing 350 to 580 kg (771.6 to 1,278.7 lb) and females 225 to 255 kg (496 to 562.2 lb).
Yaks are heavily built animals with a sturdy frame, short legs, and rounded hooves. They have small ears and a wide forehead, with smooth hollow horns that are generally dark in colour. In males, the horns sweep out from the sides of the head, and then curve forward; they typically range from 48 to 99 cm (18.9 to 39 ) in length. The horns of females are smaller, only 27 to 64 cm (10.6 to 25.2 ) in length, and have a more upright shape. Both sexes have a short neck with a pronounced hump over the shoulders, although this is larger and more visible in males.
Both sexes have long shaggy hair with a dense woolly undercoat over the chest, flanks, and thighs to insulate them from the cold. Especially in males, this may form a long "skirt" that almost reaches the ground. The tail is long, with a large plume of hair over much of its length. Wild yaks typically have black or dark brown hair over most of the body, with a greyish muzzle, although some wild golden-brown individuals have been reported. Domesticated yaks have a wider range of coat colours, with some individuals being white or
piebaldA piebald or pied animal is one that has a spotting pattern of large unpigmented, usually white, areas of hair, feathers, or scales and normally pigmented patches, generally black. The colour of the animal's skin underneath its coat is also pigmented under the dark patches and unpigmented under...
. The
udderAn udder is an organ formed of the mammary glands of female quadruped mammals, especially ruminants such as cattle, goats, sheep and deer. The udder is a single mass hanging beneath the animal, consisting of pairs of mammary glands...
in females and the
scrotumIn some male mammals the scrotum is a dual-chambered protuberance of skin and muscle containing the testicles and divided by a septum. It is an extension of the perineum, and is located between the penis and anus. In humans and some other mammals, the base of the scrotum becomes covered with curly...
in males are small and hairy, as protection against the cold. Females have four teats.
Physiology
Yak physiology is well adapted to high altitudes, having larger lungs and heart than cattle found at lower altitudes, as well as greater capacity for transporting oxygen through their blood due to the persistence of foetal haemoglobin throughout life. Conversely, yaks do not thrive at lower altitudes, and begin to suffer from heat exhaustion above about 15 °C (59 °F). Further adaptations to the cold include a thick layer of subcutaneous fat, and an almost complete lack of functional sweat glands.
Compared with domestic cattle, the
rumenThe rumen, also known as a paunch, forms the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals. It serves as the primary site for microbial fermentation of ingested feed...
of yaks is unusually large, relative to the
omasumThe omasum, also known as the bible, the fardel, the manyplies and the psalterium, is the third compartment of the stomach in ruminants...
. This likely allows them to consume greater quantities of low-quality food at a time, and to ferment it longer so as to extract more nutrients.
Odor
Yaks have some of the strongest odors of any domesticated animal, often described as a combination of cow manure and wet dog. Their thick coat of fur plays a strong role in this, as fecal and urinary odor often becomes "trapped" inside.
Reproduction and life history
Yaks mate in the summer, typically between July and September, depending on the local environment. For the remainder of the year, many males wander in small bachelor groups away from the large herds, but, as the
rutThe rut is the mating season of ruminant animals such as deer, sheep, elk, moose, caribou, ibex, goats, pronghorn and Asian and African antelope....
approaches, they become aggressive and regularly fight amongst each other to establish dominance. In addition to non-violent threat displays, bellowing, and scraping the ground with their horns, male yaks also compete more directly, repeatedly charging at each other with heads lowered or sparring with their horns. Like
bisonMembers of the genus Bison are large, even-toed ungulates within the subfamily Bovinae. Two extant and four extinct species are recognized...
, but unlike
cattleCattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
, males wallow in dry soil during the rut, often while scent-marking with urine or dung. Females enter oestrus up to four times a year, and females are receptive only for a few hours in each cycle.
Gestation lasts between 257 and 270 days, so that the young are born between May and June, and results in the birth of a single calf. The female finds a secluded spot to give birth, but the calf is able to walk within about ten minutes of birth, and the pair soon rejoin the herd. Females of both the wild and domestic forms typically give birth only once every other year, although more frequent births are possible if the food supply is good.
Calves are weaned at one year and become independent shortly thereafter. Wild calves are initially brown in colour, and only later develop the darker adult hair. Females generally give birth for the first time at three or four years of age, and reach their peak reproductive fitness at around six years. Yaks may live for more than twenty years in domestication or captivity, although it is likely that this may be somewhat shorter in the wild.
Wild yaks
Wild yaks (
Bos grunniens mutus or
Bos mutus) usually form herds of between ten and thirty animals. They are insulated by dense, close, matted under-hair as well as their shaggy outer hair. Yaks secrete a special sticky substance in their sweat which helps keep their under-hair matted and acts as extra insulation. This secretion is used in traditional
NepalNepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...
ese medicine. Many wild yaks are killed for food by hunters in China; they are now a vulnerable species.
The diet of wild yaks consists largely of grasses and sedges, such as
CarexCarex is a genus of plants in the family Cyperaceae, commonly known as sedges. Other members of the Cyperaceae family are also called sedges, however those of genus Carex may be called "true" sedges, and it is the most species-rich genus in the family. The study of Carex is known as...
,
StipaThis article is about a type of grass.For Speech Transmission Index for Public Address Systems, see Speech transmission index.For the Italian aircraft designer, see Luigi Stipa...
, and
KobresiaKobresia is a genus of plants in the sedge family. They are sometimes called bog sedges. These perennial sedges are quite similar to Carex species in appearance...
. They also eat a smaller amount of herbs,
winterfatKrascheninnikovia is a genus of flowering plants in the amaranth family known generally as winterfat. They are known from Eurasia and western North America. These are hairy perennials or small shrubs which may be monoecious or dioecious...
shrubs, and mosses, and have even been reported to eat
lichenLichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
. Historically, the main natural predator of the wild yak has been the
Tibetan wolfThe Tibetan wolf , also known as the woolly wolf, is a subspecies of grey wolf native to Central Asia from Turkestan, Tien Shan throughout Tibet to Mongolia, northern China, Shensi, Sichuan, Yunnan, and the western Himalayas in Kashmir from Chitral to Lahul. They also occur in the Korean peninsula...
, but
brown bearThe brown bear is a large bear distributed across much of northern Eurasia and North America. It can weigh from and its largest subspecies, the Kodiak Bear, rivals the polar bear as the largest member of the bear family and as the largest land-based predator.There are several recognized...
s and
snow leopardThe snow leopard is a moderately large cat native to the mountain ranges of South Asia and Central Asia...
s have also been reported as predators in some areas.
Thubten Jigme Norbu, the elder brother of Tenzin Gyatso, the 14th
Dalai LamaThe Dalai Lama is a high lama in the Gelug or "Yellow Hat" branch of Tibetan Buddhism. The name is a combination of the Mongolian word далай meaning "Ocean" and the Tibetan word bla-ma meaning "teacher"...
, reported on his journey from
KumbumA Kumbum is a multi-storied aggregate of Buddhist chapels in Tibet. It forms part of Palcho Monastery.The first Kumbum was founded in the fire-sheep year 1427 by a Gyantse prince. It has nine lhakangs or levels, is 35 metres high surmounted by a golden dome, and contains 77 chapels which line...
in
AmdoAmdo is one of the three traditional regions of Tibet, the other two being Ü-Tsang and Kham; it is also the birth place of the 14th Dalai Lama. Amdo encompasses a large area from the Machu River to the Drichu river . While culturally and ethnically a Tibetan area, Amdo has been administered by a...
to
LhasaLhasa is the administrative capital of the Tibet Autonomous Region in the People's Republic of China and the second most populous city on the Tibetan Plateau, after Xining. At an altitude of , Lhasa is one of the highest cities in the world...
in 1950:
Distribution and habitat
Wild yaks are found primarily in northern
TibetTibet is a plateau region in Asia, north-east of the Himalayas. It is the traditional homeland of the Tibetan people as well as some other ethnic groups such as Monpas, Qiang, and Lhobas, and is now also inhabited by considerable numbers of Han and Hui people...
and western
QinghaiQinghai ; Oirat Mongolian: ; ; Salar:) is a province of the People's Republic of China, named after Qinghai Lake...
, with some populations extending into the southernmost parts of
XinjiangXinjiang is an autonomous region of the People's Republic of China. It is the largest Chinese administrative division and spans over 1.6 million km2...
, and into
LadakhLadakh is a region of Jammu and Kashmir, the northernmost state of the Republic of India. It lies between the Kunlun mountain range in the north and the main Great Himalayas to the south, inhabited by people of Indo-Aryan and Tibetan descent...
in India. Small, isolated populations of wild yak are also found farther afield, primarily in western Tibet and eastern Qinghai. In historic times, wild yaks were also found in
NepalNepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...
and
BhutanBhutan , officially the Kingdom of Bhutan, is a landlocked state in South Asia, located at the eastern end of the Himalayas and bordered to the south, east and west by the Republic of India and to the north by the People's Republic of China...
, but they are now considered extinct in both countries, except as domesticated animals.
The primary
habitatA habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism...
of wild yaks consists of treeless uplands between 3000 and 5500 m (9,842.5 and 18,044.6 ft), dominated by
mountainImage:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...
s and
plateauIn geology and earth science, a plateau , also called a high plain or tableland, is an area of highland, usually consisting of relatively flat terrain. A highly eroded plateau is called a dissected plateau...
s. They are most commonly found in alpine meadows with a relatively thick carpet of grasses and sedges, rather than the more barren
steppeIn physical geography, steppe is an ecoregion, in the montane grasslands and shrublands and temperate grasslands, savannas, and shrublands biomes, characterized by grassland plains without trees apart from those near rivers and lakes...
country.
Behaviour
Yaks are herd animals. Herds can contain several hundred individuals, although many are much smaller. The
herdHerd refers to a social grouping of certain animals of the same species, either wild or domestic, and also to the form of collective animal behavior associated with this or as a verb, to herd, to its control by another species such as humans or dogs.The term herd is generally applied to mammals,...
s consist primarily of females and their young, with a smaller number of adult males. The remaining males are either solitary, or found in much smaller groups, averaging around six individuals. Although they can become aggressive when defending young, or during the rut, wild yaks generally avoid humans, and may rapidly flee for great distances if any approach.
Domesticated yaks
Domesticated yaks have been kept for thousands of years, primarily for their
milkMilk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...
, fibre and
meatMeat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...
, and as
beasts of burdenA working animal is an animal, usually domesticated, that is kept by humans and trained to perform tasks. They may be close members of the family, such as guide or service dogs, or they may be animals trained strictly to perform a job, such as logging elephants. They may also be used for milk, a...
. Their dried dung is an important fuel, used all over Tibet, and is often the only fuel available on the high treeless Tibetan plateau. Yaks transport goods across mountain passes for local farmers and traders as well as for climbing and trekking expeditions. "Only one thing makes it hard to use yaks for long journeys in barren regions. They will not eat grain, which could be carried on the journey. They will starve unless they can be brought to a place where there is grass." They also are used to draw
ploughThe plough or plow is a tool used in farming for initial cultivation of soil in preparation for sowing seed or planting. It has been a basic instrument for most of recorded history, and represents one of the major advances in agriculture...
s. Yak milk is often processed to a
cheeseCheese is a generic term for a diverse group of milk-based food products. Cheese is produced throughout the world in wide-ranging flavors, textures, and forms....
called
chhurpi in Tibetan and Nepali languages, and
byaslagMongolian cuisine refers to the local culinary traditions of Mongolia and Mongolian styled dishes. The extreme continental climate has affected the traditional diet, so the Mongolian cuisine primarily consists of dairy products, meat, and animal fats. Use of vegetables and spices is limited...
in Mongolia.
Butter made of Yaks' milkYak butter is butter made from the milk of the domesticated yak . It is a staple food item and trade item for herding communities in south Central Asia and the Tibetan Plateau...
is an ingredient of the
butter teaButter tea, also known as po cha , cha süma , Mandarin Chinese: sūyóu chá or goor goor in local Ladakhi terms, is a drink of the Tibetans and Chinese minorities in southwestern China. It is also consumed in Bhutan. It is made from tea leaves, yak butter, and salt.-Usage:Drinking butter tea is a...
that Tibetans consume in large quantities, and is also used in lamps and made into
butter sculptureButter sculptures often depict animals, people, buildings and other objects. They are best known as attractions at state fairs in the United States as lifesize cows and people, but can also be found on banquet tables and even small decorative butter pats. The earliest documented butter sculptures...
s used in religious festivities. Yaks grunt, and unlike
cattleCattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
are not known to produce the characteristic bovine lowing sound.
Shimshali Yaks
In parts of Tibet and Karakorum
yak racingYak racing is a spectator sport held at many traditional festivals of Tibet, Northern Pakistan and Mongolia, and can be one of the most entertaining parts of a Tibetan horse festival, in gatherings which integrate popular dances and songs with traditional physical games...
is a form of entertainment at traditional festivals and is considered an important part of their culture. More recently, sports involving domesticated yaks, such as
yak skiingYak skiing is a sport practiced in the Indian hill resort of Manali as a tourist attraction.The sport involves a skier waiting at the bottom of a slope and a yak at the top of the hill; yak and skier are connected by means of a rope going around a pulley at the top of the hill. To engage the yak,...
, or
yak poloYak polo is a Mongolian variant of the sport polo. It is played on yaks instead of on horseback.Originally invented in the early 2000s as a tourist attraction, the sport is as of 2006 reported to have attracted a modest following in Mongolia...
, are being marketed as tourist attractions in Central Asian countries, including Gilgit-Baltistan, Pakistan.
Hybrids
In
NepalNepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...
, Tibet and Mongolia, domestic
cattleCattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
are crossbred with yaks. This gives rise to the infertile male
dzoA dzo is a hybrid of yak and domestic cattle. The word dzo technically refers to a male hybrid, while a female is known as a dzomo or zhom. Alternative Romanizations of the Tibetan names include zho and zo. In Mongolian it is called khainag...
as well as fertile females known as
dzomo or
zhom, which may be crossed again with cattle. The "Dwarf Lulu" breed, "the only
Bos primigenius taurus type of cattle in Nepal" has been tested for DNA markers and found to be a mixture of both taurine and
zebuZebu , sometimes known as humped cattle, indicus cattle, Cebu or Brahmin cattle are a type of domestic cattle originating in South Asia, particularly the Indian subcontinent. They are characterised by a fatty hump on their shoulders, drooping ears and a large dewlap...
types of cattle (
B. p. taurus and
B. p. indicus) with yak. According to the International Veterinary Information Service, the low productivity of second generation cattle-yak crosses makes them suitable only as meat animals.
Crosses between yaks and domestic cattle (
Bos primigenius taurus) have been recorded in Chinese literature for at least 2,000 years. Successful crosses have also been recorded between yak and
American bisonThe American bison , also commonly known as the American buffalo, is a North American species of bison that once roamed the grasslands of North America in massive herds...
,
gaurThe gaur , also called Indian bison, is a large bovine native to South Asia and Southeast Asia. The species is listed as vulnerable on the IUCN Red List since 1986 as the population decline in parts of the species' range is likely to be well over 70% over the last three generations...
, and
bantengThe banteng , also known as tembadau, is a species of wild cattle found in Southeast Asia.Banteng have been domesticated in several places in Southeast Asia, and there are around 1.5 million domestic banteng, which are called Bali cattle. These animals are used as working animals and for their meat...
, generally with similar results to those produced with domestic cattle.
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