The Yak (Bos mutus), also known as "common yak", it is a mammal of the Bovidae family that lives at high elevations in the mountains of the Asian continent. It can be seen living in captivity as "domestic" animals or in wild herds..
This animal is the Asian mammal that lives at the highest altitude in the entire Asian continent, since it lives between 3,000 and 5,500 meters above sea level (masl) in the coldest, wildest and most desolate mountain ecosystems.
They are animals very well adapted to the cold: they have a thick and dense coat that protects them from freezing winds and low temperatures. They have strong legs, with large hooves to climb the rocky and steep areas where they generally live..
As well as cows, the yak also belongs to the Bovidae family, along with goats, bison, buffalo, sheep, among others. It is currently on the red list that classifies animals in danger of extinction and is classified as a "vulnerable" animal..
This classification is due to the fact that, in their natural state, their wild populations are scarce and difficult to observe. People in the Asian mountains have domesticated yaks as farm animals and depend on them for their livelihood..
They are used as pack animals by the locals of the Himalayas and the vast majority of localities located in the Asian mountains. They consume their meat as a substitute for beef, market and weave garments with fabrics that they produce from their thick fur.
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Yak are quadrupeds, looking very similar to domestic cows, that is, they have horns and a somewhat elongated snout. However, yaks have a very characteristic abundant and dense coat, which can be black, white, reddish, brown or grayish..
All species of Yaks have a shape specially adapted for existence under extreme conditions: low temperatures, high and arid places that are associated with low oxygen levels and extreme conditions solar radiation..
Its coat is made up of three different types of hair:
- Long and thick ones for protection, about 52 µm in diameter
- Other intermediates between 25 and 52 µm in diameter, "looking" all down
- And finer or thinner fibers less than 25 µm in diameter
During the winter these hairs grow abundantly (dense) especially in the neck, shoulders and back region, increasing up to 30% of the weight of the coat to withstand the cold.
Like bulls and cows, yaks have a marked sexual dimorphism; this is that females and males differ physically. Males are much larger animals than females, with much more developed antlers..
Female tak, on the other hand, are about a third the size of males, who generally weigh about 800 kg, but can reach up to 1200 kg in their adult stage..
It is important to mention that wild yaks and domesticated ones (grown in captivity) can present quite different characteristics, usually due to the differences between the conditions in which they live. Below you can see yaks from Tibet:
The remote ecosystems where yaks inhabit are located on the Tibetan plateaus and rocky regions of Ladakh in India. The extreme conditions of these places prevent trees from growing, with herbaceous plants being the dominant plant species at these heights..
Currently the coverage of wild Yak populations has been reduced towards the north of Tibet and there are only a few isolated and fragmented populations to the south and east of central Tibet and northeast of Qinghai, in China..
Poaching depleted populations during the 1990s, but since 2000 laws were created to protect the species and there has been a recovery in the number of individuals in wild herds..
In addition, there are an estimated 14 million domestic yaks in the territories between Afghanistan and eastern China. With China being the epicenter of yak breeding as domestic animals, where more than 90% of the estimated 14 million individuals are accounted for.
Based on historical evidence, the yaks are presumed to have extensive coverage over the high-altitude areas of Eurasia, as fossils have been discovered in Nepal, north of the Himalayas and in the Limi Valley. However, it is currently listed as extinct in these localities..
The yak is a herbivorous ruminant that forages grasses in the soils of tall meadows and grasses that grow between rocks. In addition, it has been observed that in the winter they consume mosses and lichens that grow on rocky slopes..
Food availability in these areas is scarce, so they do not have a very varied diet. This varies according to the seasons of the year, since there are times when some species of grasses are obtained and others when none are obtained..
An example is the short summer season, where yaks consume almost exclusively species of grasses and other herbs. This is because grasses grow rapidly during this time, stimulated by the temperature, sun and humidity of the season..
In the winter the diets are nutritionally deficient, since they do not get herbs for consumption and they feed mainly on lichens, mosses and even lick the stones to obtain some minerals.
In captivity they are kept with abundant grass, solutions rich in minerals and with water consumption at least twice a day..
In captivity, yaks have between 1 and 4 reproductive cycles, lasting 20 days during the summer. Up to 75% of domestic females conceive during their first heat of the year. Physical changes from first heat are obvious to the naked eye.
Inflammation in the vulvas of the vagina, runny secretions, raised tail and frequent urination. Most females reproduce for the first time between 3-4 years.
However, development varies with climate, latitude, elevation, and food availability. The gestation period is 260 to 270 days. It is common for between 5 and 10% of pregnant domestic females to have premature births..
Postpartum anestrus lasts approximately 125 days. The maximum productivity of domestic females is between 5 and 6 years of age. At 9 years of age, productivity drops by almost 50%.
Domestic yaks generally produce a calf every 2 years or more, and this has also been observed in wild Yaks. Most deliveries occur during the day, rarely at night.
In most cases parturition occurs standing up, although the female may spend long intervals lying down or on her side. During childbirth, females tend to acquire aggressive behavior.
The first lactation occurs between 10 and 30 minutes after delivery and can last between 5 and 15 minutes. Once the first lactation ends, the female and her calf join the herd again. A female is seen giving birth below:
There is little information on the reproductive habits of wild yaks, but observing the reproductive habits in captivity it is known that it can be in two different ways:
- Young males stay with female herds for a year or more and then separate from the herd to compete with other young males for new females and new herds..
- Other males live solitary and group together only during the summer to reproduce..
The main breeding seasons of domestic yaks correspond to the months of July-mid-August, even extending until September. The act of copulation itself usually lasts between 5 and 10 minutes.
Males reach reproductive maturity between 5 and 10 years. In the summer it is said that the males go into "heat", since they become aggressive during the reproductive season. These compete with other males by charging with the antlers, in order to reproduce with the females of the herd.
When males reach old age they are less competitive to reproduce, so they begin to live alone or in small groups and move away from the herds of females in reproductive capacity. Two yaks can be seen mating below:
The behavior of yaks varies depending on the time of year they are observed. As we have already mentioned, in the reproductive seasons the males are very aggressive, but the rest of the year the herds are quite docile..
However, wild yaks have been observed to be able to move unpredictably long distances to avoid settlements and human activity (these animals are not long distance migratory animals)
Elusive movements are usually performed on altitudinal gradients, either ascending or descending in mountains. Sometimes they move looking for better places to feed on herbs.
Yaks tend to stay in very large herds. The largest report has been 1000 individuals in a single herd. However, at present the herds are usually 100 to 200 individuals.
In the herds, males of different ages, young and large numbers of females are usually observed. On very few occasions, solitary female yaks or in groups of less than 20 individuals are observed.
Some wild yak herds associate with other ungulate species in the lower areas where they inhabit. Among these species is the Tibetan antelope, commonly known as "chiru" or the "white-lipped deer.".
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