About 170 critically-endangered golden wild yaks, a species once believed to be extinct, roam in a nature reserve in southwest China's Tibet Autonomous Region thanks to adequate protection, forestry officials said Friday.

The yaks are in Changtang Nature Reserve, a 200,000-square km area in Tibet's Ngari Prefecture where more than 400 wild animal species live in the wild, including critically endangered Tibetan antelopes, wild Tibetan donkeys and wild yaks.

The golden wild yak, known for its golden fur, is the rarest of wild yaks and unique to the Changtang reserve.

"It's very difficult to spot a golden wild yak because the animal is extremely sensitive and runs away very fast whenever they detect the smells of human beings or other animals," said Tendar, a forestry police officer in the Changtang reserve.

Unlike other wild yak species which are dark or brown and often confront human beings, these golden animals are tame and move around gracefully, he said.

The rare yaks were believed to be extinct until forestry workers found a group of 40 roaming in the wilderness of Ngari Prefecture's Rutog County in 2006.

"Today, its population has increased to about 170, thanks to our effective protection and fight against illegal poaching," said Tendar, who heads a team of 10 forestry policemen that patrol the wilderness.

The populations of many other wild animal species are also on the rise in the reserve, he said.

The number of Tibetan antelopes in the Changtang Nature Reserve has increased to 120,000, twice as much as its population in the 1990s.

The reserve has more than 80,000 wild Tibetan donkeys, compared with 50,000 in the 1990s.

China has more than 2,000 nature reserves that cover a combined 1.5 million square km.

In Tibet alone, 47 nature reserves have been set up covering 400,000 square km, said Xu Zhihong, chairman of the Chinese National Committee for UNESCO's Man and the Biosphere Programme (MAB), at the 13th China Biosphere Reserve Network Convention that opened in Lhasa on Thursday.0 The MAB has been working for 40 years in the areas of ecosystem conservation and sustainable use of natural resources.