This article focuses on the variances between the yak’s two species: Bos mutus (Wild Yak) and Bos Grunniens (Domestic Yak).
The domestic yak is a descendant of the wild yak. The variances that will be discussed will cover their sexual dimorphic, appearance, behavior, distribution, and even their conservation status.
The wild yak is a premium species of the Tibetan plateau with a remnant population of 10,000 animals.
It serves as an essential genetic resource for the enriching of its domestic counterpart. They are regularly seen in herds even though there are also pairs that may be siblings being sighted.
From time to time, solitary yaks (the bulls) are sighted as well. The wild yak has a spontaneous temperament, can get aggressive, and attack an approaching human.
The domestic yak is smaller relative to the wild yak. It is over 13 million (over 90% of the total yaks’ population) in China. They are mostly reared for their milk which is used to manufacture cheese at high altitudes.
Over the years, yak milk has attracted a huge demand. They are primarily bred for their milk, as beasts of burden, their wool, and their horns.
The coats of wild yaks typically display just a little differentiation in color. Most of their coats range from dark brown to dark reddish-brown, jet brown, and jet black. Then there has been an exceptional case of a wild yak with golden-brown coat color.
According to Schaller (1998), this is a mutation that occurs in about 2% of the animals in the Aru basin of Northwest Tibet. The presence of the golden yak is evidence of selective mating and hybridization.
Selective breeding, in this case, refers to the backcrossing between selected cattle. The purpose of this is to infiltrate the gene of a certain yak into the gene pool of another.
On the other hand, domestic yaks have an assortment of various coat colors ranging from black to white, brown, and pied. They could be grey, black, or brown with speckles or patches of white, grey, and brown.
The white yak is considered a separate breed and it is listed as a contemporary artificially-influenced breed. In North America, all-white yaks have been proven to be hybrids of cattle.
The wild yak is never white. It is simple to identify through its very short variance in coat coloring. Young wild yaks are mostly dark brown, and their pelage is usually dense with a woolen undercoat and lengthy, rough guard hairs.
The muzzle of the domestic yak has grey-white hairs around it even though the muzzle itself is either grey or black. On the other hand, wild yaks have a grey area above their muzzle tip, and they possess silver-colored hair that forms a pale ring around their muzzle tips.
Primigenius spiral horns
The wild yaks’ horns display the “primigenius spiral” which is named after the horn shape of the aurochs.
The horns extend towards the side out of their bases in a somewhat smooth curve. The horns spiral forward, upward, and inward. The aurochs and kouprey, relatives to the wild yak all exhibit this horn shape.
Although, the wild yak is the only species that is still alive out of these three. Their horns are typically very round, very thick, and are about 15 – 20 cm in diameter.
The domestic yak shows this horn shape to a certain degree but not as prominent as the wild yak. Its horn is more upright in shape than the wild yak.
The wild yak has been categorized as “Vulnerable” according to the IUCN Red List of Threatened Species. Previously, it was classified as “endangered”, but it was taken off that list due to a reduction in population decline and current population size.
In China, it is granted top-notch protection in an effort to preserve it for more selective breeding to produce hybrids and as a source of genetic materials for the domestic yak.
The last population count in 2008 recorded about 10,000 adult yaks. On the other hand, domestic yaks are thriving in population with over 13 million of them in central Asia’s highlands.
The wild yak can be found on the Tibetan plateau at elevations as high as 3,000 to 5,500 meters. This high-altitude location usually has the coldest, wildest, and the barest mountains. It is presently restricted to a small part of the Indian Ladak and the Chinese regions of Tibet, Qinghai, and Xinjiang.
There is also an isolated population of wild yaks on the border of Qinghai and Gansu and the northern side of the Tibet-Nepal border. The core population of the wild yak is concentrated around northern Tibet and northwestern Qinghai.
The domestic yak can be found all through the Himalayan region of the Indian country, the Tibetan plateau, Northern Myanmar, Yunnan, Sichuan, and even up to Siberia and Mongolia. It has a much broader range than its ancestors.
As their scientific names imply, the Bos Grunniens (Grunniens means grunting) and Bos Mutus (mutus means mute). Initially, their scientific names translate to “grunting ox” and “mute ox”.
Wild yaks have a very large and strong body, are bigger than the domestic yak, and less social. Also, their sexual dimorphism is more pronounced than the domestic yak.
Their males are much larger than their females. Female wild yaks weigh about a third of the male’s weight, and they are about 30% smaller in length.
The males measure between a range of 5.7 – 6.6 feet in height at the shoulder, and their body length measures up to about 12 feet.
The female wild yaks have a height range between 4-5 feet at the shoulder and about 10 feet of body length. In general, wild yaks can weigh between 300 – 1000kg with their tails measuring between 60 – 100 centimeters.
Domestic yaks are not as large as the wild yak. Their males weigh between 350 – 585kg, and their females weigh between 225 – 255kg.
In terms of height at the shoulders, they measure between 44 – 54 inches, and the females measure between 41 – 46 inches.
Wild yaks have a short, broad, and somewhat convex forehead. Its head isn’t as long as that of the domestic yak, but its forehead is wider. The domestic yaks have longer faces than the wild yaks, but their foreheads are skinnier and less broad.