A new monkey species - named the white-cheeked macaque - has been discovered in southeast Tibet's Modog County, reports China state news agency Xinhua.

Li Cheng, a Chinese wildlife photographer first identified the new species after he heard its call in 2012.

"It was a high-pitched 'Yi-ou' - I had never heard such a call from a macaque before," Li told Xinhua. But the group of macaques vanished into the woods before he could make them out.

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In the fall of 2013, Li joined a field survey of wild species in Tibet where he set up 31 cameras with motion sensors  in the primeval forest in Modog. The cameras took three images and a 15-second video each time they detected movement.

After six months of monitoring the forest, Li's team had accumulated 738 photos and more than 100 videos of the "special macaques" of Modog.

Then in December, Fan Pengfei, an associate professor of primate studies in Dali University, and Zhao Chao, a researcher at Southwest Forestry University, both claimed to have seen the "special macaques" in Modog.

Li, Fan and Zhao determined from the photographs that the species was distinct from all known species of macaque. The most distinguishing feature of the monkey was the regular off-white fur on the cheeks of the adults, hence the name white-cheeked macaque.

Other traits include long, thick hair on the neck, a relatively hairless short tail, and dark skin on the muzzle.

But experts say that the newly discovered species is feeling the stress of human encroachment and activities.

"Currently, Modog is the only known habitat of the white-cheeked macaque, though its range may extend to neighboring counties in China and regions of southeast Tibet controlled by India," says Li, who estimates the new species' population at about 500.

Discoveries of new species of mammals - especially primates - are rare, Li Baoguo, president of the China Primatological Society, told Xinhua.

"The white-cheeked macaque is the second new species of macaque recorded in the past century," said Li. "This discovery is significant in the study of biodiversity changes caused by human activities."

TagsNew Monkey Species Discovered in Tibet, white-cheeked macaque, Li Cheng, Modog, macaque, Fan Pengfei, Dali University, Zhao Chao