Imagine a Wild Yak (Bos mutus) is standing in front of you, munching sedges and shrubs, herbs and grass in the faraway reaches of Northern Tibet. Its black, brown and rust-toned wooly body stands up to 6’ at the shoulder, more closely resembling a mammoth than a cow. Once hunted for their meat, Wild Yaks were killed by explorers, geological surveyors, poaching gangs and meat-eating locals in numbers that brought them into catastrophic decline. Habitat reduction further impacted their success, as nomadic pastoralists with their own domestic yak herds settled into the high-altitude grasslands once the Wild Yak’s exclusive domain.
To be a cold-loving, wide-hooved, rugged Wild Yak today means to be one of some 22,000 individuals, living in small herds (5 to 33 each) spread across the Northern Tibet Plateau at altitudes ranging from 10,500 to 17,700 feet above sea level. The largest percentage (7,000 – 7,500) graze and grunt peacefully in the 284,000 square kilometers in the Chang Tang Nature Reserve, while others are content to munch sedges and shrubs in the Arjin Shan, Kekexili, Sanjiangyuan and Yanchiwan Nature Reserves. The population is beginning to rebound from the effects of overhunting and habitat loss. Just as the numbers have begun to increase, though, new challenges have surfaced: hybridization and climate change.
Hybridization, or cross-breeding, weakens the genetic integrity of a species. In the case of the Wild Yak, mounting a perhaps easier, less shy domestic female yak may be an attractant, but it is weakening the strength of the species. The Wildlife Conservation Society is working with other agencies to create buffer zones between the wild and the domestic yaks — fencing out domestic yaks – to not only provide the Wild Yak its natural grazing habitat, but also to prevent detrimental cross-breeding. (Domestic yaks may also carry Brucellosis, a disease causing spontaneous abortion in Wild Yaks.)
But what of the more pernicious and silent threat to the Wild Yak – that of climate change and its effect on habitat? According to the WCS, climate change is occurring at twice the rate on the Northern Tibetan Plateau as other places on the planet, detrimentally altering the Wild Yak’s preferred cold-weather habitat. An animal intolerant to heat, the Wild Yak’s natural plant diet of sedges and shrubs, herbs and grasses may be permanently altered or reduced as a result of the drier, hotter conditions. Moreover, rising waters in lakes and rivers may prove inviting to nomadic pastoralists, increasing yak-human conflicts.
The Wild Yak is a hardy, persistent species, indeed, surviving temperatures as low as -40 degrees below Celsius/Fahrenheit. But the effects of climate change may be more far-reaching than this species can survive. The WCS is working with the University of Montana to look into the needs of the Wild Yak relative to its ecology and peri-glacial habitat, a project that will help determine the need for further protection of its range as glaciers recede. Will the future’s Wild Yak be found grazing on sedges and shrubs, herbs and grasses once under ice? Only time will tell.
Schaller, George B and Wulin, Liu Biological Conservation: 76 (1996) Distribution, Status, and Conservation of Wild Yak