The recent discovery of a previously unrecognized species of macaque in the Tibet autonomous region is based on 738 photos mainly taken by camera traps in bio-diverse, yet poorly studied, forests in the southeast of the Tibet autonomous region.
The three scientists who discovered it have named it the white-cheeked macaque.
"Our photos clearly showed some morphological differences between the white-cheeked macaque and other known species and allowed us to claim it as a new species," said Fan Pengfei, one of the corresponding authors and a primatologist at Dali University in Yunnan province.
The newly discovered primate is distinguished from the other four macaque species in the region－Assam, Tibetan, Rhesus, and Arunachal－by the rounded glans of its penis and a dark, hairy scrotal sac, according to an article in the American Journal of Primatology.
The other macaques in the area have a spear-shaped glans and white scrotums.
As the new macaques approach adulthood, prominent white whiskers begin to grow on their cheeks and chins, which inspired the name.
These hairs grow longer with age, covering the ears of adult macaques, and giving them a round-faced appearance. "Look at the front of the white-cheeked macaques' round faces, you don't see their ears, which are hidden behind their thick hair," said Zhao Chao, co-author of the article and one of the three discoverers.
"But pointed ears are a conspicuous feature on the face of Arunachal macaque, which has no side or chin whiskers. The Assam macaque's side whiskers are less prominent, creating a triangular face," he added.
In addition to these distinctive characteristics, the new macaque also has long, thick hair around its neck and a hairless, short tail.
"The Tibetan macaque has prominent side and chin whiskers, creating a round facial appearance, but it has thin, short hair on its neck and a shorter tail," Zhao said.
Another distinctive characteristic is its odd, high-pitched alarm call.
The new discovery inhabits a wide range of habitats, from tropical forests at 1,395meters above sea level, to primary and secondary ever-green broad-leaved forests at 2,000 meters, and mixed forests of broad-leaves and conifers at 2,700 meters.
Besides living in Modog county, it's living range may extend to neighbouring counties in Tibet and even further afield.
"I only encountered the monkeys and got their photos and videos through camera traps in unspoiled primitive forests in Modog," said Li Cheng, an amateur naturalist and one of the discoverers, who set up 31 camera traps and obtained most of the photos of the macaque in the remotest county in Tibet. "I didn't find any in the area's secondary forests that are farmed via slash and burn techniques, or around villages."
There is still a large stretch of primitive forest near the county town of Modog, but a long history of animal hunting may explain why Li failed to see any of the new monkeys there.
Camera traps represent a time and labour-efficient method of data collection that has been used widely to survey mammalian diversity and behaviour, and camera traps are increasingly used in primate field studies, according to Fan.
"In Modog, it's almost the only way to get images of the monkey," Li said, adding that the major research site is at least a two-day hike from the nearest human settlement and the primitive forests are extremely difficult to traverse and can be "very dangerous".
While setting up the camera traps and then collecting the results, he encountered king cobras, tore a ligament, and became a "sponge" for hundreds of leeches.
He estimated that the population of white-cheeked macaques may number about 500, but "to get exact number will require further investigation".
"The forest in Modog is like a nature library, and we know very little about it," said Chao Zhao, a researcher at Dali University's Institute of Eastern-Himalaya Biodiversity Research. "Discovery of the new macaque species suggests that there may be some species that remain undiscovered in this area."
LiuYang, a biologist from Sun Yatsen University in Guangzhou, Guangdong province, said: "The unexpected discovery of the white-cheeked macaque means more secrets may be hidden in bio-diverse southeastern Tibet. By using more research methods, such as camera traps and DNA metabarcoding (a rapidly evolving method for assessing biodiversity), hopefully we can disclose these secrets one at a time."
But the forest is under threat from hunting by local tribes and planned construction, according to the researchers.
The local Monba and Lhoba ethnic groups set ground traps for animals, which pose a potential threat to white-cheeked macaques. Moreover, the government is planning to construct cascade hydropower stations in Modog, including in the area where the researchers photographed the macaques.
"Construction of hydropower stations would result in the destruction and flooding of extensive areas of forest along the rivers, the potential habitat of white-cheeked macaques. The immigration of a large number of people into the area to construct the hydropower stations also will result in an increase in the bush meat trade, deforestation, new roads, and the construction of housing for workers, all of which will have a negative impact on conservation of the new species," the researchers wrote in their paper.
"All of these unknown species are like rare books in the library. If you destroyed the forest, you would destroy the books in it," Zhao said. "We would lose all the knowledge in these books which might prove to be vital for the future of human beings."
Michael A. Schillaci, an anthropologist at the University of Toronto, in Canada told New Scientist magazine that given the region's isolation, people would expect to see more new species there. But he said that images alone aren't enough to classify the monkey as a new species yet. Only DNA can prove if it is truly distinct from other macaques.
However Fan pointed out that biologists use different concepts to define species－such as biological species, phylogenetic species and morphologic species－depending on the organisms and data available.
"Based on these photos, we're confident about our conclusion," Fan said. "But getting and analysing DNA samples of the monkey will certainly make our research more solid, which will be our major work in the next step."