The monkeys, known in China as Yunnan golden hair monkeys, are among the world's most endangered primates.
They live in mountainous forests in Tibet's Markam County, as well as neighboring Yunnan province's Deqin County.
The total number of black snub-nosed monkeys living in China is estimated to be more than 2,000.
Figures from the Markam county forestry bureau indicate that the number of monkeys living in the county declined sharply in the early 1990s due to poaching, state run Xinhua news agency reported.
The reproduction of the species has been hampered, as the existing monkeys live in separate regions, affecting the way genes are passed on among different natural populations.
Protective efforts by the forestry bureau have increased the population of monkeys in Markam, with the number of monkeys expected to exceed 1,000 in the future, bureau director Rinchen Phuntsog said.
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The government established a state-level nature reserve in Markam to protect the rare monkeys in 2003.
The reserve covers 185,300 hectares and is home to approximately 700 black snub-nosed monkeys.