Yunnan Snub-Nosed Monkey, Rhinopithecus bieti
YUNNAN SNUB-NOSED MONKEY
Geographic Distribution and Habitat
The Yunnan snub-nosed monkey, also referred to as the black-and-white snub-nosed monkey or black snub-nosed monkey, is endemic to the Yunnan Province of China—specifically in the Yunling mountain range in northwestern Yunnan and southeastern Tibet. This region borders the Tibet Autonomous Region to the northwest, the provinces of Sichuan to the north, Guizhou to the east, and the Zhuang Autonomous Region of Guangxi to the southeast, as well as the countries of Vietnam, Laos, and Myanmar.
The territory of this monkey is limited to a 9,600 sq mi (25,000 sq km) area of Trans-Himalayas, between the Mekong River to the west and the Yangtze River to the east—a region characterized by majestic but isolated forests, inaccessible canyons, and deep valleys.
The Yunnan snub-nosed monkey is the only non-human primate to live at such high altitudes (9800-14,700ft; 3,000-4,500m) and to survive at temperatures below 32 F (0 C) for several months. The ground here is frozen most of the year, roughly 280 days. The snow blanket can be 3.3 ft (1 m) thick from November to April.
Temperatures rise in the summer, thanks to the jungles below and the warm air funneled through the canyons from Borneo and India. The rainy season runs from May to October, but most of the rain falls between June and August.
There are three types of forests in the region: deciduous broadleaf, coniferous, and mixed broadleaf and coniferous. Because of its extremely rich biodiversity, the forest of Yunnan region is on the United Nations World Heritage list of sites that require protection.
Size, Weight, and Lifespan
The Yunnan snub-nosed monkey belongs to the Colobine family. It is rather large; adult males weigh 30 lbs (14 kg) on average and females weigh 20 lbs (9 kg). The body length varies between 20 and 32 in (51-83cm). The tail measures 20 to 29 in (52-75 cm). Information about their lifespan is unknown.
These primates look powerful, with their buddha-like belly, strong thighs, and almost woolly coat of long dark gray fur, which covers their back, arms, legs, and tail, and the top of their head. This fur is longer in males than it is in females. White-to-creamy color fur covers their armpits, chest, belly, rump, and flanks, and the tips of their ears. Their face is white—almost like that of a noble woman in ancient paintings—while their gentle jet-black, almond-shaped eyes and their prominent, punkish forelock offer a striking contrast. Their lips are thick and pink, and their nose is upturned and deprived of nasal bones. The length of their tail is equal to or slightly longer than the length of their body. Both hands and feet have five digits, including opposable thumbs, and are covered in fur on the top and bare on the inside. Their fingernails are black. Their top canines are powerful, and much longer and wider than the other teeth.
Babies are born completely white, with pink toes and Yoda-like ears. Their fur darkens gradually as they grow up.
The diet of the Yunnan snub-nosed monkey varies slightly, depending on its distribution. Troops found in the coniferous forests of the southern region mostly consume lichens that grow on fir trees. Troops living farther north in the coniferous and broadleaf forests add non-lichen food items—such as leaves of different plant species—to their diet. Although lichens are slow to regenerate (15 years), they are an abundant food source (especially Bryoria and Usnea) and constitute the majority of this monkey’s diet. During the harsh winters, lichens are pretty much the only food source available. Fortunately, the Yunnan snub-nosed monkey’s stomach is able to extract nutrients and digest protein-poor, toxic lichens that contain indigestible carbohydrates. Bamboo leaves, which are ubiquitous and non-seasonal, are another common choice on the menu. Bamboo shoots are especially good for nursing mothers.
Food items are most diverse in the spring, so the snub-nosed monkeys are able to supplement their diet with grasses, moss, bark, tubers, flowers, fruit, berries, pine nuts, acorns, mushrooms, seeds, beetles, spiders, and even the nectar of poisonous rhododendron flowers. They prefer young leaves to mature leaves because they are more nutritious and lower in fiber. When available, they prefer mature leaves of deciduous trees, which are easier to digest, however they have been observed eating entire branches of evergreen trees that they occasionally completely defoliate.
They drink water from ponds and streams, but have been occasionally observed eating snow in the winter.
Behavior and Lifestyle
Yunnan snub-nosed monkeys live in a multilevel society with bands or troops ranging from 20 to 300 individuals. Each band includes several families composed of a cohesive core of one adult male and three to five females with their young, called one-male units (OMUs).
Usually, groups keep to a distance of at least 10 ft from each other to avoid any risk of animosity between males. Intergroup interactions are rare. The troops may travel up to 1 mile a day (1,500 m) within their 9.7 sq mi (25 sq km) home range.
Although they are comfortable and move faster on the ground, Yunnan snub-nosed monkeys spend most of their time in the trees.
Zoologist Alphonse Milne-Edwards (1835-1900) was the first to identify the Yunnan snub-nosed monkey in 1897 and named the species Rhinopithecus bieti.
Lichen-eating is rare in primates and has only been observed in a handful of other species living in mountainous regions.
The troop starts traveling to the feeding site early in the morning—on cloudy days they arrive a little later. They forage together for a few hours, nap in the middle of the day, and forage some more in the afternoon. They spend about 10% of their time traveling to feeding sites, 35% feeding, and 39% resting. They are otherwise engaged in diverse actives such as grooming.
They travel longer distances to feed in the warmer months. They move slower when the rain is heavy or if there is a snowstorm.
They like to rest on rocky outcrops, which may give them an advantage in spotting predators. Since outcrops are exposed to the sun, they also provide a source of warmth, especially in winter.
When the night falls, the troop retires together at sunset, no matter the season. Groups huddle together to keep warm. They enter the sleeping tree one by one—the mother and baby first, at the center, the other females, then the males on each side of them, holding on to each other tight. It is interesting to note that male juveniles only seem to huddle together to sleep at night. The adult male of the OMU is always the last one to enter the sleeping tree. The individuals huddling are usually from the same OMU. Once settled, they all stop moving and become very quiet. They sleep for about 11 hours, sometimes a little more when it snows.
Huddling reduces the surface of the body exposed to the elements and seems to be an effective strategy to cope with low temperatures. The mother and baby being at the center also provides them with more protection and safety. The largest huddles include eight individuals.
In the morning, when the troops depart for the day, there does not seem to be a preset order of which individuals (by age or sex) leave the sleeping tree first.
Like most primates, Yunnan snub-nosed monkeys communicate both visually and vocally. Standing on all fours, front limbs apart showing strong shoulders while pulling the lips back to reveal powerful incisors and gums, is a sure way to threaten and intimidate another monkey. Barks express anger, whereas giggly chirps are playful. Alarm calls are used to tell the group about predators approaching or looming danger.
Males reach sexual maturity at five or six years of age, whereas females reach maturity at four or five. The mating season spans the months of August and September and females only give birth to one offspring every two to three years, after a gestation period of 200 days. The mother is the central figure of the family, but it is not unusual for other members of a OMU to take care of a baby, carrying, grooming, and even nursing him or her. Usually these are adult or subadult females, but the father can sometimes provide shelter and comfort to a baby. Some females have also been observed playing the role of midwives, helping the mother while she is giving birth.
When the mother goes foraging or moves around, the baby clings to her belly by her fur. Babies are fragile. They are vulnerable to injuries and deadly attacks from predators or even conspecifics. After the loss of an infant, a grieving mother will continue to carry the corpse for a few days.
Play activities are essential for the young to learn how to interact with other monkeys.
Like other monkeys who are herbivores, Yunnan snub-nosed monkeys disperse seeds through their feces—thereby helping to regenerate their forest habitat.
The Yunnan snub-nosed monkey is one of the most prized protected species in China. The species is classified as Endangered in the International Union for Conservation of Nature Red List of Threatened Species (IUCN, 2015).
Recent statistics indicate that there are 15 isolated groups left, which represent an overall population of approximately 1,000 mature individuals.
Deforestation and climate change are the main causes of the species’ decline. The forests are cleared for agriculture and rapid industrialization. It is estimated that in the last 40 years, the suitable habitat for the Yunnan snub-nosed monkey has decreased by 31%. The average patch size is down to 2 sq mi (5.4 sq km) from 6 sq mi (15.6 sq km).
Habitat fragmentation and the lack of forest corridors contribute to the genetic isolation and inbreeding of southern troops, especially because the southern Yunnan region is most influenced by human presence. It contains more artificial barriers than the northern region. Furthermore, where there are corridors, they do not necessarily cross habitat that is suitable for the survival of the snub-nosed monkeys. These gentle creatures are also at risk from poaching—many lose limbs in snares set for deer, and sometimes get poisoned by pesticides used by the forestry department for pest control.
The Yunnan region is one of the richest in terms of biodiversity, with 18,000 plant species, 900 bird species, and 620 fish species—not to mention the snub-nosed monkeys. As such, the region is the focus of many conservation efforts.
In 1999, a ban stopped most commercial logging in the region and slightly curbed habitat loss. Many ideas were promoted over the years, including the production of biogas to replace firewood and the promotion of high yield grasses to feed livestock, for example.
A captive breeding program at the Kunming Zoo and Kunming Institute of Zoology was created to save the Yunnan snub-nosed monkey. However the continual pressure on the region is growing and a more comprehensive approach was needed.
Between 1958 and 2010, the population in the Yunnan region grew from 16 to 48 million, causing increased pressures for development. This is why the Yunnan Province Biodiversity Conservation Strategy and Action Plan (2012-2030) was created. It aims at protecting biodiversity, limiting human encroachment in protected areas, and controlling human activities while promoting economic development. The Yunnan Environmental Protection Bureau also has a plan to mitigate the effects of climate change. Their experts know that by 2050, the areas of very cold weather will have decreased by 70%. Temperatures have risen at a steady rate of 0.25% since 1960 and there were 13 warm winters since 1986. Rainfalls are fewer and droughts are more frequent. The agency is therefore working to create movement corridors in existing protected areas. It also promotes awareness to ensure wildlife needs are included in economic plans. Another of its goals is to modify existing laws and get funding for protected areas.
Hopefully this is good news for the Yunnan snub-nosed monkeys.
- PBS – Mystery Monkeys of Shangri-La documentary from award-winning filmmaker, Xi Zhinong.
- National Geographic Wild website
- Influence of Day Length, Ambient Temperature, and Seasonality on Daily Travel Distance in the Yunnan Snub-Nosed Monkey at Jinsichang, China – Red Baoping, Li Ming, Long Yongcheng, Wei Fuwen.
- Maternal responses to dead infants in Yunnan snub-nosed monkey (Rhinopithecus bieti) in the Baimaxueshan Nature Reserve, Yunnan, China – Tengfei Li, Baoping Ren, Dayong Li, Yunbing Zhang, Ming Li.
- Nocturnal Sleeping Habits of the Yunnan Snub-Nosed Monkey in Xiangguqing, China – Dayong Li, Baoping Ren, Cyril C. Grueter, Baoguo Li, Ming Li.
- Overwintering strategy of Yunnan snub-nosed monkeys: adjustment in activity scheduling and foraging patterns – Cyril C. Grueter, Dayong Li, Baoping Ren, Ming Li.
- Habitat Degration of Rhinopithecus beiti in Yunnan, China – Wen Xiao, Wei Ding, Liang-Wei Cui, Ru-Liang Zhou, Qi-Kun Zhao.
- Human Pressures on Natural Reserves in Yunnan Province and Management Implications – Cheng Qiu, Jinming Hu, Feiling Yang, Feng Liu, Xinwang Li.
- Tibet Nature Environmental Conservation Center website
- IUCN Red List
Written by Sylvie Abrams, April 2018