Wild Yak
Tagged: animal, animals, cat, mammalBos grunniens ( images )
The ultimate “survival machine,” the sturdy yak is in its element even in the harshest Himalayan winter conditions. However, it is not adapted to deal with the threats of hunting, habitat disturbance, and competition from its domesticated relatives. Yaks are the eastern equivalent of the American bison, and they are among the hardiest mammals on earth. Between 2,000 and 3,000 years ago the yak’s ancestors were successfully domesticated and used for milk, beef, and wool production. Domestic yaks were also used as pack and draft animals, and their dried dung served as fuel on the Tibetan plateau, which has no trees. Today the world population of domestic yaks is probably over 12 million. By contrast, wild yaks are now extremely rare: Recent estimates have put the population at just a few hundred animals. An immensely hardy animal, the yak survives seemingly without difficulty on the hostile, high plateaus of the Himalayas, enduring winter conditions among the harshest on earth. Temperatures in this area can fall to as low as -15°F (-26°C). The yak uses heat generated by plant material fermenting in its intestines to help keep warm; adult yaks are also covered in thick, woolly hair. However, with such adaptations to the extreme cold yaks are not so tolerant of warm temperatures. Herds that move to lower pastures to bear young in spring retreat as summer arrives, returning to altitudes of about 15,000 feet (4,550 m), where there is snow all year round. Yaks are social animals, and most individuals will spend their lives as part of a herd. The largest herds are made up of females and young, with bachelor males forming smaller bands. There are obvious advantages to living in a group; formidable as fully grown yaks are, they still have at least one serious natural predator, namely, the Tibetan wolf.
Sure-Footed Climbers
The scarcity of good food in its habitat forces the yak to wander widely in search of grasses, lichens, and other low-growing alpine plants. Deep snow is hard to walk through, but the yaks save energy by walking in single file, stepping into the footprints of the animal in front. Each large cloven hoof is augmented with an enlarged dewclaw (a partly developed extra hoof), which gives a strong grip. Despite their bulk, the yaks are sure-footed climbers, able to hop from rock to rock to avoid the deepest snowdrifts. Only in the worst storms and blizzards do they come to a halt to wait out the weather, standing in small groups with their heads turned away from the driving wind and icy snow.
On the Brink of Extinction
The wild yak should surely be thriving in a habitat where no other species can match its power and suitability for the environment. It suffers from only moderate predation and has very little natural competition. However, as is so often the case, this magnificent example of natural design is being pushed to the brink of extinction by the actions of humans. Wild herds are hunted throughout much of their range; and as human settlements have expanded, yaks are finding themselves outcompeted by domestic herds or in some cases simply assimilated into them. Wild and domestic yaks often interbreed. Consequently, the genetic purity of the wild type has been diluted, and the offspring are less able to cope with life in the wild.
Wild yak
Bos grunniens
- Family: Bovidaeli
- World population: Fewer than 1,000
- Distribution: Tibetan plateau (northern Tibet); Kansu in northwestern China; eastern Kashmir in India
- Habitat: Alpine tundra and steppe; spends summer above snow line
- Size: Length: up to 10.6 ft (3.3 m); height at shoulder: up to 6.5 ft (2 m); females about 60% smaller than males. Weight: males 670-2,200 lb (300-1,000 kg); females lighter than males
- Form: Massive ox with dense, brown-black woolly hair. High humped shoulders; low-slung head. Both sexes have curved horns
- Diet: Grasses, herbs, and lichens
- Breeding: Adults mate in winter; a single calf is born in the following fall. Life span up to 25 years
- Related endangered species: American bison (Bison bison)
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