GRAY SNUB-NOSED MONKEY

Rhinopithecus brelichi

Geographic Distribution and Habitat

The gray snub-nosed monkey, also known as the Brelich’s snub-nosed monkey, Guizhou snub-nosed monkey, and Guizhou golden monkey, is endemic to the Fanjingshan National Nature Reserve within the Wuling Mountains of Guizhou province, China. They are found in mixed deciduous and evergreen broadleaf forests at elevations of 4,593-7,546 feet (1,400-2,300 m) during the summer, and move down to 1,870 feet (570 m) during times of heavy snow cover.

They are thought to utilize most of the available range of the nature reserve. The annual rainfall in the area above 5.249 feet (1,600 m) elevation is above 79 inches (2,000 mm). Snow is common during the winter months, with below-freezing temperatures for about five months of the year. However, monthly average temperatures are never below 32ºF (0ºC).

TAXONOMIC NOTES

Based on a recently published genomic study (June 2023), the gray snub-nosed monkey is a hybrid of the golden snub-nosed monkey (R. roxellana) and a species that is an ancestor of the Yunnan snub-nosed monkey (R. bieti).

Gray snub-nosed monkey geographic range encircled in red. Map: IUCN, 2023

Size, Weight, and Lifespan

The gray snub-nosed monkey stands at 25-29 inches (64-74 cm) tall, with a tail length ranging from 28-38 inches (70-97 cm). Males are roughly twice as heavy as females, with the former weighing in at around 33 pounds (15 kg) on average, while females weigh in on average at 17.6 pounds (8 kg).

There is no recorded lifespan for the gray snub-nosed monkey, but one of their closest relatives, the golden snub-nosed monkey is thought to live for 20-25 years.

Appearance

Adult gray snub-nosed monkeys are covered in fine, long fur, usually brown on the upper body to gray on the lower body, with a white patch between the shoulder blades. Their neck, head, and extremities of the limbs are black, save for their golden-colored regal forehead. The chest is also golden, and chestnut fur is found on their inner knees and inner sides of their arms. Their bare face is blueish-white in color with full lips, pink around their nose and eyes, and their shelf-like brow and reduced nasal bones give them their snub-nosed appearance. Along with their weight, sexual dimorphism is further expressed with males being more brightly-colored than females, and with white skin around the nipple area.

Juveniles are various shades of gray, with their coat patterns changing as they age.

Photo courtesy of Cyril C. Grueter, PhD and used with permission.
Diet

The gray snub-nosed monkey is an omnivore, with a diet that varies based on the season. Half of their diet consists of leaves, with a nearly even split between young and mature leaves. The seasonality of their forest habitat means their diet changes seasonally as well. Based on one study published in 2012, the following was recorded as their diet from each season: 

  • In spring they feed on mainly young leaves and flowers
  • During summer they consume young leaves and unripe fruits and seeds
  • Autumn is dedicated to ripe fruits and seeds
  • Winter consists of buds and more mature leaves

Other items in their diet include insects and insect larvae, bark, petioles (the stalk that attaches the leaf blade to the stem), and even birds and bird eggs.

Behavior and Lifestyle

The gray snub-nosed monkey is diurnal (most active during the day) and semi-terrestrial. Where available, they primarily inhabit trees but are not averse to traveling on the ground. Locomotion around their habitat consists of a mix of quadrupedal walking, leaping, climbing, semi-brachiation, and occasional full brachiation.

Gray snub-nosed monkeys spend their days foraging with a rest period in the middle of the day, followed by further foraging, before descending to particular roost areas at night to sleep. No nests are made. Most roost locations are used once, while others may be used multiple times. In a study published in 2010, researchers observed the monkeys using 15 different night roost locations, and 36-day roost locations; accordingly, night roost reuse was higher than that of day roosts. The study suggested that the daily altitudinal movement patterns of the gray snub-nosed monkey may reflect a trade-off between finding food and avoiding predation within their habitat. 

Predators of the gray snub-nosed monkey include the clouded leopard (Neofelis nebulosa) and humans.

Fun Facts

The gray snub-nosed monkey was initially described in 1903 from a hunted pelt, and was believed to be extinct until 1962, when a skull was found. The first living individual, a female, was found by researchers five years later.

Daily Life and Group Dynamics

The gray snub-nosed monkey’s social structure is based on small groups of 5-10 individuals consisting of a dominant male, a harem of females, and their offspring. These groups might band together temporarily into larger groups numbering hundreds of individuals. Although groups can be antagonistic toward one another on a typical day, individuals become friendlier towards one another when forming “supergroups”. Babies in one group have been observed playing with those from other groups while a single male watches over the group. These supergroups travel, feed, and sleep together, and split into large or smaller groups seasonally.   

Bachelor groups, consisting of two to five adult or sub-adult males, will keep close to the periphery of a troop, waiting for an opportunity to take over leadership of a harem. 

The daily routine of the gray snub-nosed monkey can be summarized from a couple of studies from the early 2000s to 2010. In the morning (6:30 AM in summer, 7:40 AM in winter), gray snub-nosed monkeys depart their night roost and move to higher elevations towards a morning feeding site, upon which they feed until 11:00 AM (summer)/noon (winter). After this feeding session, they rest at a day roost until 2:00 PM (summer)/3:30 (winter), upon which they travel to an afternoon feeding site and continue foraging until 4:30 PM (summer)/5:30 PM (winter). The movement between feeding sites and day roosts is mostly horizontal (i.e., little to no change in elevation). Finally, once satiated, the monkeys travel to the night roost, which is at a lower elevation than their feeding sites and day roosts, at 7:35 PM (summer)/6:00 PM (winter).

Communication

There is a lack of significant research regarding communication of gray snub-nosed monkeys, likely due to their remote location and scarcity. What is known regarding this specific species is that individuals coordinate their movements by communicating through distinctive vocal patterns. Simple contact calls resemble the whine of a human baby, while a “hoo-chuck” alarm call warns others of potential danger.

Knowledge regarding communication of the golden snub-nosed monkey can provide potential information regarding communication of their gray cousins. Due to their large nostrils, golden snub-nosed monkeys can communicate “ventriloquially”. This means that vocalizations can occur without mouth movement. Since gray snub-nosed monkeys have similar nostrils, they may be able to communicate the same way. The golden snub-nosed monkey has a rich repertoire of vocalizations which can number at least 18 individual calls. This is linked to the fact that they often gather in groups numbering hundreds of individuals; in such groups, individual calls must be separate and distinct from one another to be understood by group members. Since gray snub-nosed monkeys gather in similarly large groups, they likely have a similar vocalization range.

Ultimately, further research is needed on the gray snub-nosed monkey and their communication habits.

Reproduction and Family

Breeding occurs between summer and autumn, with peak breeding activity occurring in September. Females give birth to a single offspring between March and May, with an interval of three years between births. Females reach maturity at around six years of age and typically give birth to their first young at around nine years of age. Males, by comparison, reach maturity at three years of age, upon which they will leave their natal group, while females typically stay. Males and females often wait two to three years before mating for the first time. While the reason is unknown among males, for females, this is usually to ensure their body has fully matured and is healthy enough to take on the role of parenthood.

Infants are carried by their mothers for the first month of life, after which they gradually reach independence before being weaned off of their mother’s milk between 12 and 20 months of age. 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.

Photo: © 中国物种信息系统/ iNaturalist/Creative Commons
Ecological Role

With fruits and seeds making up around a quarter to a third of their diet, gray snub-nosed monkeys are critical seed dispersers within their limited habitat. Seeds that survive the digestion process are deposited far from their parent tree through defecation. This creates a more diverse and healthier habitat, benefiting local plant and animal species. 

Conservation Status and Threats

The International Union for Conservation of Nature lists the gray snub-nosed monkey as Critically Endangered (IUCN, 2022), appearing on the IUCN Red List of Threatened Species. The species is also assessed as Critically Endangered on the Red List of China’s Vertebrates.

The gray snub-nosed monkeys’ population continues to decline, with an estimated number of only 200 mature individuals remaining. The continued degradation of the quality of their small habitat is due to human activities, namely tourism and infrastructure construction. Habitat loss is also exacerbated by forest clearing and illegal mining. Historically, the gray snub-nose monkey has also been the victim of illegal hunting for meat and use in traditional medicine, and occasional trapping by snares intended for other animals.

The Fanjingshan National Nature Reserve, where the gray snub-nosed monkey lives, is smaller than 38.5 square miles (100 km²). Within the reserve, their total area of occupancy is estimated to be only 10.5 square miles (27-28 km²). The construction of a tram, along with roads and cable cars within the reserve, has contributed to the monkey’s reduced area of occupancy. Occupying such a small area also makes the gray snub-nosed monkey vulnerable to natural disasters and outbreaks of disease.

A 2020 study based on direct field operations to calculate the population density of the reserve’s gray snub-nosed monkeys found that the remaining population totals only between 125 to 336 individuals (with mature individuals only making up a portion of this total). 

Finally, the existing population of gray snub-nosed monkeys is vulnerable to inbreeding which results in decreased genetic diversity. This lower genetic variability makes it difficult for the gray snub-nosed monkey to adapt to both environmental and climate change.

Conservation Efforts

The gray 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.

The gray snub-nosed monkey is also listed as a Category I species under the Chinese Wildlife Protection Act of 1989. The publication of the latest population sizes and group numbers by authorities on the reserve continues to be an urgent priority.

The Fanjingshan National Nature Reserve contains a captive breeding colony to assist in building a healthy population of gray snub-nosed monkeys. There have also been discussions regarding the relocation of some monkeys to neighboring reserves, in order to enable the species to diversify and become less susceptible to disease, natural disasters, and other potential threats (a process known as ex-situ conservation). Fanjingshan was designated as a World Heritage Site in 2018, which is composed of not only the Fanjingshan National Nature Reserve, but also Yinjiang Yangxi Provincial Nature Reserve, and a small area of the National Non-Commercial Forest.   

Overall, a plethora of conservation actions, such as land and timber harvest management, further public education and awareness, the enforcement of stricter laws and policies within the reserve, and continued investigation into the possibility of ex-situ conservation, alongside further research on the species as a whole, are needed to save the gray snub-nosed monkey from the brink of extinction.

References:
  • https://www.bioexplorer.net/animals/mammals/monkeys/gray-snub-nosed-monkey/
  • https://brill.com/view/journals/ijfp/81/4/article-p233_6.xml
  • https://en.wikipedia.org/wiki/Gray_snub-nosed_monkey
  • https://www.google.com/books/edition/The_Natural_History_of_the_Doucs_and_Snu/x2awA0IDVA8C?hl=en&gbpv=1&printsec=frontcover
  • https://www.gbif.org/species/4267005
  • https://www.iucnredlist.org/species/19595/215621115
  • https://newscenter.sdsu.edu/360/news.aspx?v=print&s=51435
  • https://news.cgtn.com/news/3d3d774e3349544e34457a6333566d54/index.html
  • https://onlinelibrary.wiley.com/doi/abs/10.1002/ajp.20645
  • https://primate.wisc.edu/primate-info-net/pin-factsheets/pin-factsheet-golden-snub-nosed-monkey/
  • https://www.researchgate.net/publication/221811579_Diet_and_Feeding_Behavior_of_Rhinopithecus_brelichi_at_Yangaoping_Guizhou
  • http://ruffordorg.s3.amazonaws.com/media/project_reports/Biological%20Conservation%20142%20%282009%29%20469-476.pdf
  • https://www.sciencedirect.com/science/article/abs/pii/S0006320708004461
  • https://www.science.org/doi/10.1126/science.abl4997
  • https://whc.unesco.org/en/list/1559/

Written by Sienna Weinstein, January 2024