Yunnan Snub-Nosed Monkey, Rhinopithecus bieti
YUNNAN SNUB-NOSED MONKEY
Rhinopithecus bieti
Geographic Distribution and Habitat
The Yunnan snub-nosed monkey, also known as the black snub-nosed monkey or black-and-white snub-nosed monkey, is found in the region of Tibet and Yunnan Province in southwestern China. Specifically, they are found in fragmented populations within the Yunling Mountains in northwestern Yunnan Province and southeastern Tibet, at elevations ranging between 1.86-2.92 miles (3,000-4,700 m). These mountains are west of the Yangtze River, and east of the Mekong River.
Within this mountain range, the Yunnan snub-nosed monkey is found in deciduous broadleaf, coniferous, and mixed broadleaf and coniferous forests. As the only nonhuman primate to live in such high altitudes, which are notable for thin air and below-freezing temperatures (32ºF or 0ºC), these monkeys have unique adaptations that allow them to survive in such extreme conditions!
Size, Weight, and Lifespan
The Yunnan snub-nosed monkey is a rather large species. Adult males weigh around 30 pounds (14 kg), while females weigh in at 20 pounds (9 kg). The body length may vary between 20 and 32 inches (51-83 cm), while the tail measures from 20-29 inches (52-75 cm). This difference in size is an example of sexual dimorphism (noticeable physical differences between genders in addition to genitalia).
Information about their lifespan is undocumented.
Appearance
The Yunnan snub-nosed monkey is covered with an almost wooly coat of long dark gray fur, which extends across the back, arms, legs, tail, tops of the feet and hands, and the top of the head. This fur is longer in males than it is in females—another example of sexual dimorphism—and serves as the perfect coat to keep the monkeys toasty warm in their often cold habitat. Armpits, chest, Buddha-like belly, flanks, rump, and ear tips are covered in white to cream-colored fur. Also white, almost like that of a noblewoman in ancient paintings, is the face, which contrasts with the prominent, pinkish forelock (a tuft of hair) above the gentle, jet-black, almond-shaped eyes. The lips are pink and thick, and the nose is upturned and lacks nasal bones, hence the name “snub-nosed”.
Both hands and feet are bare on the inside and have five digits, including opposable thumbs, and the fingernails are black. The top set of canine teeth are powerful, and much longer and wider than the other teeth.
Babies, meanwhile, are born completely white, with pink toes and Yoda-like ears. Their fur gradually darkens as they grow older.
Diet
The Yunnan snub-nosed monkey is an omnivore, eating both plant and animal material. Unlike many primates, the primary item in their diet (two-thirds, to be exact) is lichen found on trees. Lichens serve as a reliable year-round food supply, growing in abundance in mountainous regions like those in which the Yunnan snub-nosed monkey is found. Lichens are toxic to most animals, but the Yunnan snub-nosed monkey is prepared with specialized digestive enzymes similar to those of a cow that remove the harmful bacteria and extract the ever-important nutrients.
If the opportunity arises, the Yunnan snub-nosed monkey will also eat bamboo leaves, fruit, and other, more seasonal plants. Many food items vary depending on the geographic location of individual troops, and especially, the season. The Yunnan snub-nosed monkey’s diet is most diverse during Spring, and along with their favorite lichen, may include grasses, moss, bark, tubers, flowers, berries, buds, 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 also prefer mature leaves of deciduous trees, which are easier to digest, however, they have been observed eating entire branches of evergreen trees.
As for water, they drink from ponds and streams but have occasionally been observed eating snow in the winter.
Behavior and Lifestyle
The Yunnan snub-nosed monkey is diurnal, most active during daylight hours, and arboreal, spending most of their time in the trees. They are not averse to traveling on the ground, however. With regard to locomotion, if we look at the gray snub-nosed monkey (R. brelichi), we can surmise that the Yunnan snub-nosed monkey likely also uses a mix of quadrupedal (on all fours) walking, leaping, climbing, semi-brachiation, and occasional full brachiation. Brachiation is the acrobatic swinging from tree-to-tree. During the winter months, the Yunnan snub-nosed monkey will move to the highest parts of their home range, despite the colder temperatures. This is due to a greater abundance of that ever-important lichen at higher elevations.
Like other snub-nosed monkeys, the troop begins to travel to the feeding site early in the morning. They forage for a few hours, rest 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. The remaining portion of their activity budget is engaging in various activities such as grooming and playing.
They travel longer distances to feed during the warmer months, move more slowly when there’s heavy rain or a snowstorm, and spend more time feeding during winter. Take it from these monkeys: winters should be spent eating plenty of food and moving around less! They also like to rest on rocky outcrops, which may give them an advantage in spotting predators. Since these outcrops are exposed to the sun, they also provide a source of warmth, especially in winter.
When night falls, the troop retires together at sunset, regardless of the season. They enter the sleeping tree one by one—the mother and baby first, at the center, then the other females, then the males on each side of them, holding on to each other tightly in a big huddle to keep everyone warm and protected. They sleep for about 11 hours, sometimes a little more when it snows.
Finally, predators of juvenile Yunnan snub-nosed monkeys include bears and birds of prey. Known predators of adults include humans.
Funeral rituals: It’s rare to find bodies of dead Yunnan snub-nosed monkeys. Why? When a monkey dies, troop-mates will collect leaves and bury the body. Whether this is a social behavior, or for practical reasons remains unknown today.
I’m sneezin’ in the rain: Due to their particular nose type, all snub-nosed monkeys sneeze quite often when it rains.
Shangri-la? Shangri-yah! (Sorry!): The Yunling mountain region’s lush valleys which the Yunnan snub-nosed monkey calls home may have served as inspiration for “Shangri-la”, an unspoiled earthly paradise described in the 1933 novel Lost Horizon by British author James Hilton.
The Yunnan snub-nosed monkey lives in a home range that varies between 7.3-52.12 square miles (20-135 square km), and troops may travel up to a mile (1.61 km) per day. They live in a massive multi-level society with bands or troops ranging from 20-500 individuals! These “super troops” tend to split up into smaller troops during times of food scarcity, such as during winter. Each troop 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 feet (3.05 m) from each other to avoid any risk of aggression between males. Intergroup interactions are rare.
Upon reaching maturity, males will leave their natal troop to form troops of their own. Females might do the same voluntarily, but they’re more likely to remain in their natal troop for life.
Very few studies have been conducted regarding the communication repertoire of the Yunnan sub-nosed monkey. If we look at the highly-studied golden snub-nosed monkey (R. roxellana), we can get a good idea about how Yunnan snub-nosed monkeys make themselves and their intentions known.
Golden snub-nosed monkeys are very vocal, and produce up to 18 types of calls! They have a remarkable ability to communicate in a ventriloquist-like manner, showing no visible sign of moving their mouth. However, their vocalizations often correspond with facial movements, another important aspect of primate communication. Whines, chattering, moans, and shrills are made when expressing affection or aggression, warning of danger, and during peaceful periods of eating, playing, or resting. Contact calls are used when troops may group together to form their “super troops”, and at the approach of strangers. It is also common for individuals or family groups to emit calls together like a choir for several seconds at a time. Golden snub-nosed monkeys, like other primates, also communicate through postures and facial expressions. For example, crouching showcases submission, while shrugging the shoulders and staring at another individual with a closed mouth indicates aggression.
Yunnan snub-nosed monkeys are polygynous, meaning one male gets the exclusive right to mate with multiple females. As a general rule, receptive females initiate mating, announcing their readiness through various postures and signals. Breeding can occur year-round, but peak breeding season is usually between August and September. After a gestation (pregnancy) period of six to seven months, females give birth to a single infant. Females typically give birth once every two or three years.
For the first few weeks after birth, the delicate young are carried only by the mother. At the age of six months, infants are able to obtain most of their food themselves, but the mother may continue to nurse them for another six to 14 months. Should an infant pass away, the grieving mother will continue to carry the corpse of her baby for a few days.
All of the females in a troop help one another in raising the young. While males may occasionally play with their offspring, they don’t play much of a parental role aside from protection. Females may also assist one another in the birthing process as “midwives”.
Males reach sexual maturity at five or six years of age, whereas females reach maturity at four or five.
As some of their diet consists of seeds and fruit, the Yunnan snub-nosed monkey aids in the regeneration of their forest habitat by dispersing seeds through their feces as they move around the habitat. They additionally play a role in pollination. Like bees and butterflies, they collect pollen from flowers while drinking nectar. They then deposit the pollen on each flower they visit, thereby pollinating the plants. Finally, they may also be considered pest controllers through their consumption of insects.
The International Union for Conservation of Nature lists the Yunnan snub-nosed monkey as Endangered (IUCN, 2015), appearing on the IUCN Red List of Threatened Species.
The major threat facing the Yunnan snub-nosed monkey is hunting, often as a non-targeted species caught in snares set for musk deer. However, in some locations, a strong local tradition of hunting for monkey meat and parts for use in traditional “medicine” persists.
The Yunnan snub-nosed monkey is also threatened by habitat loss, especially from logging. Since 1999, when a ban stopped most commercial logging in the region, habitat loss has slowed but remains a large potential threat for the future. In addition, fires set for agriculture are a threat in some areas, particularly in Tibet. In addition, a subpopulation of about 50 individuals in one area was wiped out due to pesticide spraying to control forest pests.
The Yunnan snub-nosed monkey is listed in Appendix I of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
Most of the remaining populations of Yunnan snub-nosed monkeys are in protected areas, with only four groups found outside these sites. Some of the protected areas that contain groups of Yunnan snub-nosed monkeys include: Hongla Snow Mountain Nature Reserve in Tibet (which contains about 300 individuals), Baima Snow Mountain and Laojun Mountain Nature Reserves in Yunnan, and Yunling Nature Reserve, also in Yunnan.
There is also a major focus in China on captive breeding of this monkey, with breeding pairs at the Kunming Zoo and Kunming Institute of Zoology. However, most of these individuals are wild-caught, and so far, the program has not been sustainable.
Conservation actions needed include properly enforced land/water and site/area protection and management, and heightened awareness, communications, and education regarding the species to locals who live alongside this adorable primate.
Finally, additional research is needed on the Yunnan snub-nosed monkey’s population size, distribution, and trends, life history and ecology. Greater monitoring of their population trends must be enacted so that the species has hope of surviving the looming plight of extinction.
- https://academic.oup.com/cz/article/68/3/265/6350481
- https://www.alltheworldsprimates.org/Members/Home/MasterPrimate.aspx?tid=591
- https://animalia.bio/black-snub-nosed-monkey
- https://en.wikipedia.org/wiki/Black-and-white_snub-nosed_monkey
- https://www.fabionodariphoto.com/en/yunnan-black-snub-nosed-monkey/
- https://www.iucnredlist.org/species/19597/17943738
- https://link.springer.com/article/10.1007/s10329-012-0293-7
- https://www.nathab.com/know-before-you-go/asia-the-pacific/china/wildlife-guide/golden-snub-nosed-monkey/
- https://news.cgtn.com/news/189510-2/index.html
- https://onlinelibrary.wiley.com/doi/abs/10.1002/ajp.20641
- https://onlinelibrary.wiley.com/doi/abs/10.1002/ajp.20871
- https://www.pbs.org/wnet/nature/blog/featured-creature-black-snub-nosed-monkey/
- https://www.researchgate.net/publication/233538189_Overwintering_strategy_of_Yunnan_snub-nosed_monkeys_Adjustments_in_activity_scheduling_and_foraging_patterns
- https://tibetnature.net/en/yunnan-snub-nosed-monkey/
Written by Sienna Weinstein, October 2024