The yak is a large artiodactyl animal of a very exotic species. A characteristic feature by which it can be distinguished from other members of the genus is long and shaggy hair, hanging almost to the ground. Wild yaks once ranged from the Himalayas to Lake Baikal in Siberia, and were still abundant in Tibet in the 1800s.
Origin and Description
Fossils of the domestic yak and its wild ancestor date back to the Pleistocene period. For the past 10,000 years, the yak has developed on the Qinghai-Tibet Plateau, which stretches for about 2.5 million km². Although Tibet is still the center of distribution of the yak, domesticated yaks are already found in many countries, including the American mainland.
Yak is usually referred to as cattle. Yet, mitochondrial DNA analysis to determine the evolutionary history of yaks has been inconclusive. Perhaps the yak is different from cattle, and there are suggestions that it is more like a bison than other members of its assigned genus.
That's interesting! A close fossil relative of the species, Bos baikalensis, has been found in eastern Russia, suggesting a possible route by which the yakoid ancestors of today's American bison may have entered the Americas.
The wild yak was tamed and domesticated by the ancient Qiang people. Chinese documents from ancient times (8th century BC) testify to the long-established role of the yak in the culture and life of the people. The wild species of yak was originally designated by Linnaeus in 1766 as Bos grunniens (“a subspecies of the domestic yak”), but this name is now thought to apply only to the domesticated form, with Bos mutus (“mute ox”) being the preferred name for wild form.
Some zoologists continue to consider the wild yak a subspecies of Bos grunniens mutus, in 2003 the ICZN passed an official regulation allowing the use of the name Bos mutus for wild individuals, and today it has a more common use.
The domestic yak (B . grunniens) – a long-haired bull found in the Himalayan region of the Indian subcontinent, on the Tibetan plateau and even in the north of Mongolia and in Russia – comes from a wild yak (B. mutus). The ancestors of the wild and domestic yak split and diverged from Bos primigenius one to five million years ago.
Appearance and Features
Yaks are heavily built animals with a voluminous body, strong legs, rounded cloven hooves, and extremely dense elongated fur that hangs below the belly. While wild yaks are more often dark (blackish to brown), domestic yaks can be very variable in color, with patches of rust, brown, and cream. They have small ears and a wide forehead with dark horns.
In males (bulls), the horns come out from the sides of the head, and then bend forward, have a length of 49 to 98 cm. The horns of females are smaller than 27–64 cm, and more straight. Both sexes have a short neck with a pronounced hump on the shoulders, although this is more noticeable in males. Domestic male yaks weigh from 350 to 585 kg. Females weigh less — from 225 to 255 kg. Wild yaks are much heavier, bulls reach a weight of up to 1000 kg, females – 350 kg.
Depending on the breed, male domestic yaks are 111–138 cm tall at the withers, while females — 105–117 cm. Wild yaks are the largest animals in their range. Adults are about 1.6-2.2 m tall. The length of the head and body is from 2.5 to 3.3 m, excluding the tail from 60 to 100 cm. Females weigh about a third less and have linear dimensions of about 30% less than males.
Interesting fact! Domestic yaks grunt and, unlike cattle, do not produce the characteristic bovine sound of a low moo. This inspired the yak's scientific name, Bos grunniens (grunting bull). Nikolai Przhevalsky named the wild variant of the yak B. mutus (silent bull), believing that it does not make sounds at all.
Both sexes have a long, shaggy coat with a thick woolly undercoat on the chest, sides, and thighs to insulate them from the cold. By summer, the undercoat falls out and is used by local residents for household needs. In bulls, the coat can form a long “skirt”, which sometimes reaches the ground.
The tail is long and similar to the tail of a horse, and not the tail of cattle or bison. The udder of females and the scrotum of males are hairy and small to protect against the cold. Females have four nipples.
Where does the yak live?
Wild yaks are found in northern Tibet + western Qinghai, with some populations spreading to the southernmost regions of Xinjiang and Ladakh in India. Small, isolated populations of wild individuals are also found far away, mainly in western Tibet + eastern Qinghai. In former times, wild yaks lived in Nepal and Bhutan, but are now considered extinct in both countries.
The habitat consists mainly of treeless uplands between 3000 and 5500 m, dominated by mountains and plateaus. They are most often found in the alpine tundra with relatively thick carpet of grasses and sedges, rather than in the more barren terrain.
Curious fact! The physiology of the animal is adapted to high altitudes, since its lungs and heart are larger than those of cattle at low altitudes. Also, the blood has a unique ability to carry large amounts of oxygen due to the high content of fetal (fetal) hemoglobin throughout life.
Conversely, yaks experience problems at low altitudes and suffer from overheating at temperatures above where -something 15 °C. Adaptation to cold consists of a heavy layer of subcutaneous fat and an almost complete absence of sweat glands.
In Russia, yaks, in addition to zoos, are found only in households in such regions as Tuva (about 10,000 heads) + Altai and Buryatia (in single copies).
Besides Tibet, domestic yak is popular with nomads :
Under the USSR, the domestic species of the yak was adapted in the North Caucasus, but did not take root in Armenia.
What does the yak eat?
Wild yak mainly lives in three areas with different vegetation: alpine meadows, alpine steppe and desert steppe. Each habitat has large areas of grassland but differs in grass/shrub type, amount of vegetation, average temperature and rainfall.
The diet of wild yaks consists mainly of grasses and sedge. But they also eat small moss bushes and even lichens. Ruminants migrate seasonally to the lower plains to feed on the more succulent grass. When it gets too warm, they retreat to higher plateaus to feed on mosses and lichens, which they scrape off the rocks with rough tongues. When they need to drink water, they eat snow.
Compared to livestock, the stomach of yaks is unusually large, which allows them to consume a large amount of low-quality food at a time and digest it longer to extract the maximum amount of nutrients.
That's interesting! Yaks consume 1% of food relative to their body weight daily, while cattle require 3% to maintain a working condition.
Contrary to popular belief, the yak and its dung have little to no odor, which can be detected when properly kept in pastures or paddocks with sufficient access to food and water. Yak wool is resistant to odors.
Character and lifestyle features
Wild yaks spend most of their time on grazing, sometimes moving to different areas depending on the season. They are herd animals. Herds can consist of several hundred individuals, although many are much smaller. They mostly live in herds of 2 to 5 individuals for single male herds and 8 to 25 individuals for female herds. Females and males live separately for most of the year.
Large herds consist mainly of females and their cubs. Females graze 100 m above males. Females with young yaks tend to choose pastures on high, steep slopes. Groups gradually move to lower altitudes during the winter. Wild yaks can become aggressive when protecting young or during mating season, they usually avoid humans and can run long distances if approached.
It is interesting! According to N. M. Przhevalsky, who first described the wild yak, back in the 19th century, herds of yak-cows with small calves used to number several hundred, or even thousands of heads.
In 6-8-year-old B.grunniens reach sexual maturity. They for the most part don't care about warm weather and prefer colder temperatures. The life expectancy of a yak is about 25 years.
Social Structure and Reproduction
Wild yaks mate during the summer, from July to September, depending on the local environment. One calf is born the next spring. During the year, bull yaks roam in small groups of bachelors away from large herds, but as mating season approaches, they become aggressive and regularly fight each other to establish dominance.
In addition to non-violent displays of threats, roars and scratches ground with their horns, yaki bulls also compete with each other using physical contact, repeatedly banging their heads down against each other or interacting with sparring with their horns. Like bison, males wallow on dry soil during the rut, often with the smell of urine or droppings.
Females enter oestrus up to four times a year, but are only receptive for a few hours each cycle. The gestation period lasts from 257 to 270 days, so that young calves are born between May and June. The female finds a secluded place to give birth, but the baby is able to walk about ten minutes after birth, and the pair is soon reunited with the herd. Females of both wild and domestic forms usually give birth only once a year.
The calves are weaned after one year and become independent soon after. Wild calves are brown at first and only later develop darker adult hair. Females usually give birth for the first time at three or four years of age and reach their peak reproductive state by about six years of age.
Natural enemies of yaks
The wild yak has a very keen sense of smell, it is vigilant, timid and tends to immediately run away, sensing danger. The artiodactyl will readily run away, but if angered or cornered, it becomes violent and attacks the intruder. In addition, yaks take other defensive actions: snorting loudly and attacking a perceived threat.
- Tibetan wolves (Canis lupus);
People (Homo Sapiens).
Historically, the main natural predator of the wild yak has been the Tibetan wolf, but brown bears and snow leopards have also been considered predators in some areas. They probably preyed on young or weak wild lone yaks.
Adult yaks are well armed, very ferocious and strong. A pack of wolves can only attack them in an exceptional situation, if the pack is large enough or in deep snow. Bull yaks can attack any pursuer, including humans, without hesitation, especially if they are injured. The attacking yak holds its head high, and its fluffy tail flutters like a plume of hair.
Human poaching almost caused the animal to completely disappear. After 1900, Tibetan and Mongolian pastoralists and military personnel hunted them almost to the point of complete extermination. The population was almost on the verge of extinction, and only the efforts of conservationists gave the yaks a chance for further development.
Population and species status
There are many factors that lead to the decline in the number of wild B. grunniens. The current population is estimated at about 15,000. Through their grazing activities, yaks play an important role in the recycling of nutrients in ecosystems.
With their broad hooves and hardiness, domesticated yaks are a great relief to the inhabitants of the Tibetan Plateau. The fine fur of young animals is used to make clothes, while the long fur of adult yaks is used to make blankets, tents, etc. Yak milk is often used to produce large quantities of butter and cheese for export.
Interesting fact! In some areas where firewood is not available, manure is used as fuel.
The wild counterpart of B. grunniens performs many of the same economic functions, albeit to a lesser degree. Despite the fact that China has established a punishment for hunting wild yaks, they are still being hunted. Many local farmers consider them their only source of meat during the harsh winter months.
There are also negative consequences from herds of artiodactyls. Wild yaks destroy fences and, under some extreme conditions, kill domesticated yaks. In addition, in areas where wild and domestic yak populations live side by side, there is a potential for disease transmission.
The Tibetan Forestry Bureau makes significant efforts to protect yaks, including fines of up to $600. However, hunting is difficult to suppress without a mobile patrol unit. The wild yak is today considered vulnerable by the IUCN. Previously classified as critically endangered, the animal was listed in 1996 based on an estimated rate of decline.
The wild yak is under threat from several sources:
- Poaching, including commercial poaching, remains the biggest threat;
- The destruction of males due to their habit of wandering alone;
- Crossing wild and domestic individuals. This may include the transmission of diseases in cattle;
- Conflicts with shepherds causing retaliatory killings for wild herds of domesticated yaks.
By 1970, wild yak was on the brink of extinction. Excessive hunting of wild yaks for food forced them to leave the plateau regions and settle at even higher altitudes, above 4500 m and right on the mountain tops at an altitude of 6000 m. Some individuals survived in the Chinese Kunlun mountains, and due to protective measures of the Chinese government , today wild herds reappeared at altitudes from 4000 to 4500 meters.
Thanks to timely protection measures, the yak began to restore its population. In recent years, there has been a spread of the species and a slight growth dynamics. However, due to improved access to much of the area by road transport and increased illegal hunting, the survival of wild yaks is not guaranteed.