| Wild yak Temporal range: Early Pliocene – Recent | |
|---|---|
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| Stuffed specimen in the ANSP, Pennsylvania | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Family: | Bovidae |
| Subfamily: | Bovinae |
| Genus: | Bos |
| Species: | B. mutus |
| Binomial name | |
| Bos mutus Przewalski, 1883 | |
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| Distribution of wild yak | |
| Synonyms | |
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The wild yak (Bos mutus) is a large, wild bovine native to the Himalayas. It is the ancestor of the domestic yak (Bos grunniens).
The ancestor of the wild and domestic yak is thought to have diverged from Bos primigenius at a point between one and five million years ago. [2] The wild yak is now normally treated as a separate species from the domestic yak (Bos grunniens). [3] Based on genomic evidence, the closest relatives of yaks are considered to be bison, which have historically been considered members of their own titular genus, rendering the genus Bos paraphyletic. [4]
Relationships of members of the genus Bos based on nuclear genomes after Sinding, et al. 2021. [5]
| Bos |
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The wild yak is among the largest extant bovid species. Adults stand about 1.6 to 2.05 m (5.2 to 6.7 ft) tall at the shoulder, and weigh 500–1,200 kg (1,100–2,600 lb). The head and body length is 2.4 to 3.8 m (7.9 to 12 ft), not counting the tail of 60 to 100 cm (24 to 39 in). [6] The females are about one-third the weight and are about 30% smaller in their linear dimensions when compared to bull wild yaks. Domesticated yaks are somewhat smaller. [7] [8] [9] [10]
They are heavily built animals with a bulky frame, sturdy legs, and rounded cloven hooves. To protect against the cold, the udder in females and the scrotum in males are small, and covered in a layer of hair. Females have four teats. Both sexes have long shaggy hair, with a dense woolly undercoat over the chest, flanks, and thighs for insulation against the cold. In males especially, this undercoat may form a long "skirt" that can reach the ground. The tail is long and horse-like, rather than tufted like the tails of cattle or bison. The coat is typically black or dark brown, covering most of the body, with a grey muzzle (although some wild golden-brown individuals have been reported). Wild yaks with gold coloured hair are known as the wild golden yak (Chinese :金色野牦牛; pinyin :jīnsèyě máoniú). They are considered an endangered subspecies in China, with an estimated population of 170 left in the wild. [11]
Two morphological types have been identified, so-called Qilian and Kunlun. [6]
Wild yaks once ranged up to southern Siberia to the east of Lake Baikal, [12] with fossil remains of them being recovered from Denisova Cave, [13] but became extinct in Russia around the 17th century. [14] Today, wild yaks are found primarily in northern Tibet and western Qinghai, with some populations extending into the southernmost parts of Xinjiang, and into Ladakh 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 Bhutan, but they are now considered extinct there. [1]
The primary habitat of wild yaks consists of treeless uplands between 3,000 and 5,500 m (9,800 and 18,000 ft), dominated by mountains and plateaus. They are most commonly found in alpine tundra with a relatively thick carpet of grasses and sedges rather than the more barren steppe country. [15]
The wild yak was thought to be regionally extinct in Nepal in the 1970s, but was rediscovered in Humla in 2014. [16] [17] This discovery later made the species to be painted on Nepal's currency. [18]
The diet of wild yaks consists largely of grasses and sedges, such as Carex , Stipa , and Kobresia . They also eat a smaller amount of herbs, winterfat shrubs, and mosses, and have even been reported to eat lichen. Historically, the main natural predator of the wild yak has been the Himalayan wolf, but Himalayan black bears, Himalayan brown bears and snow leopards have also been reported as predators in some areas, likely of young or infirm wild yaks. [11]
Thubten Jigme Norbu, the elder brother of the 14th Dalai Lama, reported on his journey from Kumbum in Amdo to Lhasa in 1950:
Before long I was to see the vast herds of drongs with my own eyes. The sight of those beautiful and powerful beasts who from time immemorial have made their home on Tibet's high and barren plateaux never ceased to fascinate me. Somehow these shy creatures manage to sustain themselves on the stunted grass roots which is all that nature provides in those parts. And what a wonderful sight it is to see a great herd of them plunging head down in a wild gallop across the steppes. The earth shakes under their heels and a vast cloud of dust marks their passage. At nights they will protect themselves from the cold by huddling up together, with the calves in the centre. They will stand like this in a snow-storm, pressed so close together that the condensation from their breath rises into the air like a column of steam. The nomads have occasionally tried to bring up young drongs as domestic animals, but they have never entirely succeeded. Somehow once they live together with human beings they seem to lose their astonishing strength and powers of endurance; and they are no use at all as pack animals, because their backs immediately get sore. Their immemorial relationship with humans has therefore remained that of game and hunter, for their flesh is very tasty.
— Thubten Norbu, Tibet is My Country [19]
Wild yaks are herd animals. Herds can contain several hundred individuals, although many are much smaller. Herds consist primarily of females and their young, with a smaller number of adult males. On average female yaks graze 100m higher than males. Females with young tend to choose grazing ground on high, steep slopes. [20] The remaining males are either solitary, or found in much smaller groups, averaging around six individuals. Groups move into lower altitude ranges during the winter. [1] Although wild yaks can become aggressive when defending young, or during the rut, they generally avoid humans, and may flee for great distances if approached. [11]
Wild yaks mate in summer and give birth to a single calf the following spring. [21] Females typically only give birth every other year. [11]
The wild yak is currently listed as Vulnerable on the IUCN Red List. It was previously classified as Endangered, but was downlisted in 1996 based on the estimated rate of population decline and current population sizes. The latest assessment in 2008 suggested a total population of no more than 10,000 mature individuals. [1]
The wild yak is experiencing threats applied by several sources. Poaching, including commercial poaching, has remained the most serious threat; males are particularly affected because of their more solitary habits. Disturbance by and interbreeding with livestock herds is also common. This may include the transmission of cattle-borne diseases, although no direct evidence of this has yet been found. Conflicts with herders themselves, as in preventive and retaliatory killings for abduction of domestic yaks by wild herds, also occur but appear to be relatively rare. Recent protection from poaching particularly appears to have stabilized or even increased population sizes in several areas, leading to the IUCN downlisting in 2008. In both China and India, the species is officially protected; in China it is present in a number of large nature reserves. [1]
The wild yak is a reservoir for zoonotic diseases of both bacterial and viral origins. Such bacterial diseases include anthrax, botulism, tetanus, and tuberculosis. [22]
A bison is a large bovine in the genus Bison within the tribe Bovini. Two extant and numerous extinct species are recognised.
Bovines comprise a diverse group of 10 genera of medium to large-sized ungulates, including cattle, bison, African buffalo, water buffalos, and the four-horned and spiral-horned antelopes. The members of this group are classified into loose tribes rather than formal subgroups, as the evolutionary relationships within the groups are still uncertain. General characteristics include cloven hooves and usually at least one of the sexes of a species having true horns. The largest extant bovine is the gaur.
Bos is a genus of bovines, which includes, among others, wild and domestic cattle.
The gaur is a bovine native to South Asia and Southeast Asia, and has been listed as Vulnerable on the IUCN Red List since 1986. The global population was estimated at a maximum of 21,000 mature individuals in 2016, with the majority of those existing in India.
The goa, also known as the Tibetan gazelle, is a species of antelope that inhabits the Tibetan plateau.
The cinereous vulture is a large raptor in the family Accipitridae and distributed through much of temperate Eurasia. It is also known as the black vulture, monk vulture and Eurasian black vulture. With a body length of 1.2 m, 3.1 m (10 ft) across the wings and a maximum weight of 14 kg (31 lb), it is the largest Old World vulture and largest member of the Accipitridae family.
The yak, also known as the Tartary ox, grunting ox, or hairy cattle, is a species of long-haired domesticated cattle found throughout the Himalayan region of Gilgit-Baltistan, Nepal, Sikkim (India), the Tibetan Plateau (China), Tajikistan and as far north as Mongolia and Siberia. It is descended from the wild yak.
The gayal, also known as the Drung ox or mithun, is a large domestic cattle distributed in Northeast India, Bangladesh, Myanmar and in Yunnan, China.
The kouprey, also known as the forest ox and grey ox, is a possibly extinct species of forest-dwelling wild bovine native to Southeast Asia. It was first scientifically described in 1937. The name kouprey is derived from the Khmer language and means "forest ox".
The banteng, also known as tembadau, is a species of wild bovine found in Southeast Asia.
The Tibetan antelope or chiru is a medium-sized bovid native to the northeastern Tibetan plateau. Most of the population live within the Chinese border, while some scatter across India and Bhutan in the high altitude plains, hill plateau and montane valley. Fewer than 150,000 mature individuals are left in the wild, but the population is currently thought to be increasing.
The bharal, also called the blue sheep, is a caprine native to the high Himalayas. It is the only member of the genus Pseudois. It occurs in India, Bhutan, China, Myanmar, Nepal, and Pakistan. The Helan Mountains of Ningxia have the highest concentration of bharal in the world, with 15 bharals per km2 and 30,000 in total.
The kiang is the largest of the Asinus subgenus. It is native to the Tibetan Plateau in Ladakh India, northern Pakistan, Tajikistan, China and northern Nepal. It inhabits montane grasslands and shrublands. Other common names for this species include Tibetan wild ass, khyang and gorkhar.
The argali, also known as the mountain sheep, is a wild sheep native to the highlands of western East Asia, the Himalayas, Tibet, and the Altai Mountains.
A bovid hybrid is the hybrid offspring of members of two different species of the bovid family. There are 143 extant species of bovid, and the widespread domestication of several species has led to an interest in hybridisation for the purpose of encouraging traits useful to humans, and to preserve declining populations. Bovid hybrids may occur naturally through undirected interbreeding, traditional pastoral practices, or may be the result of modern interventions, sometimes bringing together species from different parts of the world.
The wild water buffalo, also called Asian buffalo, Asiatic buffalo and wild buffalo, is a large bovine native to the Indian subcontinent and Southeast Asia. It has been listed as Endangered in the IUCN Red List since 1986, as the remaining population totals less than 4,000. A population decline of at least 50% over the last three generations is projected to continue. The global population has been estimated at 3,400 individuals, of which 95% live in India, mostly in Assam. The wild water buffalo is the most likely ancestor of the domestic water buffalo.
The Alpine musk deer is a musk deer species native to the eastern Himalayas in Nepal, Bhutan and India to the highlands of Tibet.
Yak butter is butter made from the milk of the domestic yak. Many herder communities in China, India, Mongolia, Nepal, Gilgit-Baltistan Pakistan and Tibet produce and consume dairy products made from yak's milk, including butter. Whole yak's milk has about twice the fat content of whole cow's milk, producing a butter with a texture closer to cheese. It is a staple food product and trade item for herder communities in south Central Asia and the Tibetan Plateau.
Chang Tang National Nature Reserve lies in the northern Tibetan Plateau. It is the third-largest land nature reserve in the world, after the Northeast Greenland National Park and Kavango-Zambezi Transfrontier Conservation Area, with an area of over 334,000 km2 (129,000 sq mi), making it bigger than 183 countries. Administratively, it lies in Xainza County and Biru County of the Nagqu Prefecture. With the more recently established adjoining reserves listed below there is now a total of 496,000 km2 of connected Nature Reserves, which represents an area almost as large as Spain and bigger than 197 other countries.
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