Animal Diversity Web

Diversity

The genus Rhinopithecus contains five currently recognized species commonly called snub-nosed monkeys. These species include golden snub-nosed monkeys (Rhinopithecus roxellana), Yunnan snub-nosed monkeys (Rhinopithecus bieti), gray snub-nosed monkeys (Rhinopithecus brelichi), Tonkin snub-nosed monkeys (Rhinopithecus avunculus), and as of 2010, Myanmar snub-nosed monkeys (Rhinopithecus strykeri). The genus Rhinopithecus is part of the subfamily Colobinae in the family Cercopithecidae. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Geissman, et al., 2020; Long, et al., 2020; Long, et al., 2022; Quyet, et al., 2020; Starr, 2022; Yongcheng and Richardson, 2021)

Geographic Range

Snub-nosed monkeys are native to the Palearctic and Oriental biogeographic regions, east of the Himalayan Mountains. Most Rhinopithecus species have highly localized geographic ranges, often in montane forest regions.

Of the five described species, golden snub-nosed monkeys (Rhinopithecus roxellana) have the largest known geographic range, which extends along the eastern border of the Tibetan Plateau. Yunnan snub-nosed monkeys (Rhinopithecus bieti) only have disjunct populations among the Yun Ling Mountains, between the Yangtze and Mekong Rivers. Gray snub-nosed monkeys (Rhinopithecus brelichi) are only known to live within the Fanjingshan National Nature Reserve, located in the Wuling Mountains. However, it is suspected that the range of gray snub-nosed monkeys may extend into the Yangxi Provincial Nature Preserve, located nearby. Tonkin snub-nosed monkeys (Rhinopithecus avunculus) are have few known populations restricted to areas in northeastern Vietnam, east of the Red River. Finally, Myanmar snub-nosed monkeys (Rhinopithecus strykeri) have been found in scattered populations in the Salween-N'mai Hka divide of Myanmar, in the Maw River watershed, along the eastern slopes of the Gaoligong Mountains, and in Nujiang Grand Canyon National Park. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Geissman, et al., 2020; Long, et al., 2020; Long, et al., 2022; Quyet, et al., 2020; Starr, 2022; Yongcheng and Richardson, 2021)

• Biogeographic Regions
• palearctic
  • native
• oriental
  • native

Habitat

Snub-nosed monkey species occupy mostly montane forest environments ranging in elevation from 200 to 4,700 m above sea level. The forests they live in vary in vegetative structure depending on geographic area, and include coniferous, deciduous, bamboo, and rhododendron forests.

Some snub-nosed monkey species, including Yunnan snub-nosed monkeys (Rhinopithecus bieti), gray snub-nosed monkeys (Rhinopithecus brelichi), and golden snub-nosed monkeys (Rhinopithecus roxellana) exhibit elevational migrations, moving to higher elevations in summer and lower elevations in winter. Gray snub-nosed monkeys in particular move to forested river valleys in winter. Although they have not been directly observed to migrate, it is suspected that Myanmar snub-nosed monkeys (Rhinopithecus strykeri) also migrate seasonally. Because Tonkin snub-nosed monkeys (Rhinopithecus avunculus) tend to live in areas at low elevations, they are unlikely to exhibit the same migration behavior. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Geissman, et al., 2020; Long, et al., 2020; Long, et al., 2022; Quyet, et al., 2020; Starr, 2022; Yongcheng and Richardson, 2021)

• Habitat Regions
• temperate
• tropical
• terrestrial

• Terrestrial Biomes
• taiga
• forest
• rainforest
• mountains

Systematic and Taxonomic History

The genus Rhinopithecus is part of the tribe Presbytini, which includes all Asian colobine monkeys. Snub-nosed monkeys are closely related to douc langurs (genus Pygathrix), proboscis monkeys (genus Nasalis), and pig-tailed langurs (genus Simias), all of which are also in the tribe Presbytini. This tribe is part of the subfamily Colobinae in the family Cercopithecidae, which includes all Old World monkeys.

The genus Rhinopithecus was originally defined in the 19th century by the French zoologist Henri Milne-Edwards. All but one of the currently recognized Rhinopithecus species have been identified based on the original definition by Henri Milne-Edwards. However, gray snub-nosed monkeys (Rhinopithecus brelichi) were originally classified as a species of douc langur in 1903 and were only later reclassified as a species of snub-nosed monkey. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; "Rhinopithecus A. Milne-Edwards, 1872", 2022; Starr, 2022)

• Synonyms

  • Pythagrix brelichi (invalid)

• Synapomorphies

  • Flat nose
  • Forward-facing nostrils
  • Large lips

Physical Description

Snub-nosed monkey species are characterized by their flat noses and forward-facing nostrils. Golden snub-nosed monkeys (Rhinopithecus roxellana) and Myanmar snub-nosed monkeys (Rhinopithecus strykeri) also have skin folds that partially cover their nostrils, which are currently suspected to protect them against frostbite in montane environments. Snub-nosed monkeys have stout bodies, black, almond-shaped eyes, and thick, protrusive upper lips.

Snub-nosed monkey species vary in weight. The average weight of males in the genus Rhinopithecus can be ordered from greatest to least: golden snub-nosed monkeys (Rhinopithecus roxellana; 19.9 kg), Myanmar snub-nosed monkeys (Rhinopithecus strykeri; 17 kg), gray snub-nosed monkeys (Rhinopithecus brelichi; 15 kg), Yunnan snub-nosed monkeys (Rhinopithecus bieti; 14 kg), and Tonkin snub-nosed monkeys (Rhinopithecus avunculus; 13.7 kg). Snub-nosed monkeys exhibit sexual dimorphism, with males being larger than females, on average. Sexes also differ in fur coloration, nipple and genital coloration, and the presence of fur crests (in males only). Generally, male snub-nosed monkeys are more colorful than females. Additionally golden snub-nosed monkey males have warts at the corners of their mouths, which are suspected to communicate sexual maturity. The sexually dimorphic characteristics that snub-nosed monkeys exhibit vary between species and subspecies. Thus, they can be helpful for field identification of sex, age, species, and subspecies. For example the three golden snub-nosed monkey subspecies have unique pelage coloration. In general, newborn snub-nosed monkeys have pale-white or cream-colored fur, which gradually darkens as they reach maturity. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Harding and Han, 2018; Starr, 2022)

• Other Physical Features
• endothermic
• bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes colored or patterned differently
• male more colorful
• sexes shaped differently
• ornamentation

Reproduction

Snub-nosed monkeys are polygynous. They typically live in family units or all-male social units. Family units often consist of one dominant male, up to 10 females, and their offspring. Younger mature males will compete violently to overthrow dominant males and win breeding rights to the associated harem of females. In some cases, multiple family units come together to form troops, and multiple troops will form larger groups, called bands. In troops and bands, dominant males from several family units may join together to ward off intruding males. Females have also been observed interfering with sexual intercourse, supposedly to increase their chances of rearing young the following year.

Mating behaviors have been best observed in golden snub-nosed monkeys (Rhinopithecus roxellana). Females initiate copulation with two behaviors. Firstly, females may make explicit eye contact with a dominant male and initiate a game of chase. Secondly, females may bend over, tuck their heads toward their chests, and splay their arms out, in an act known as "chest curling." Females may also direct their genitals towards a dominant male. Dominant males are receptive to these female-initiated mating behaviors about half of the time. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Kirkpatrick and Grueter, 2010; Li and Zhao, 2007; Starr, 2022)

• Mating System
• polygynous
• cooperative breeder

Snub nosed monkeys reach sexual maturity at different ages depending on their sex; females reach maturity after four to five years whereas males reach maturity after five to seven years. Once males reach maturity, they disperse from their natal group to challenge dominant males in other social groups. Sexually mature females typically remain with their natal family group for life. In golden snub-nosed monkeys (Rhinopithecus roxellana), dominant males will force their male offspring out of the family unit once they reach approximately three years of age.

Snub-nosed monkeys have different mating seasons depending on the species. For example, Yunnan snub-nosed monkeys (Rhinopithecus bieti) mate from August through September whereas golden snub-nosed monkeys mate from September through November. In some cases, females will copulate again soon after giving birth. Female snub-nosed monkeys gestate their young for around seven months. Infants are weaned after their first year, but remain within their family groups even after they are independent from their parents. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Kirkpatrick and Grueter, 2010; Li and Zhao, 2007; Starr, 2022)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
• viviparous

Dominant male snub-nosed monkeys defend their family units year-round. Females that are pregnant and females that are not pregnant receive similar protection from dominant males. Aside from protecting the family group as a whole, dominant males provide very little parental care for their offspring. Females within social groups have been observed aiding other females during parturition and caring for infants that are not their own. Females will groom, nurse, shelter, and carry juveniles even if they are not their immediate offspring. Newborn and young juvenile snub-nosed monkeys cling to the bellies of females before they are fully weaned, which takes around a year. In instances where an infant dies, females have been observed carrying the body of their infants for several days. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Starr, 2022)

• Parental Investment
• altricial
• male parental care
• female parental care
• pre-fertilization
  • protecting
    • male
    • female
• pre-hatching/birth
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • male
    • female
• pre-independence
  • protecting
    • male
• post-independence association with parents

Lifespan/Longevity

There is limited information regarding the longevity of snub-nosed monkeys. Captive golden snub-nosed monkeys (Rhinopithecus roxellana) and gray snub-nosed monkeys (Rhinopithecus brelichi) have been reported to live an average of 23 years. They may have similar lifespans in the wild, but are at higher risk of mortality due to predation, disease, and environmental exposure. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Starr, 2022)

Behavior

Snub-nosed monkeys are primarily arboreal and scansorial. Although they spend most of their time in trees, they will also forage on the ground in open areas. Most snub-nosed monkeys are seasonally migratory, moving from higher elevations in the summer to lower elevations in the winter.

Snub-nosed monkeys have complex, multi-level social hierarchies composed of family units or all-male units. Multiple units may live together in larger troops, and multiple troops may form large bands with as many as 600 individuals. Family units typically consist of one dominant male, a harem of up to 10 females, and their juvenile offspring. All-male units consist of small groups of nonbreeding males. Dominant males that are part of large troops or bands have been observed working together to defend their group from intruding males or potential predators.

Troops and bands often form in the summer, when resources are abundant. During the winter, when food sources are often limited to lichens and bark, there is more intraspecific competition between different family groups. Dominant males from different groups fight each other and females will occasionally fight amongst themselves. Within family groups, snub-nosed monkeys will often huddle together to share warmth in cold conditions. Snub-nosed monkeys keep their infants at the center of these huddles to provide them with maximum protection. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Geissman, et al., 2020; Geissmann, et al., 2011; Grueter, et al., 2012; Kirkpatrick and Grueter, 2010; Li, et al., 2010; Long, et al., 2020; Long, et al., 2022; Quyet, et al., 2020; Starr, 2022; Yongcheng and Richardson, 2021)

• Key Behaviors
• arboreal
• scansorial
• diurnal
• motile
• migratory
• territorial
• social
• colonial
• dominance hierarchies

Communication and Perception

Snub-nosed monkeys are diurnal primates and thus heavily rely on visual stimuli to perceive their environment. Eyesight is important for foraging, spotting danger, transmitting visual social cues, and timing daily activity patterns. Snub-nosed monkeys also use acoustic stimuli to detect predators and to communicate intraspecifically.

Extensive studies of snub-nosed monkey communication have only been conducted on two species: Yunnan snub-nosed monkeys (Rhinopithecus bieti) and golden snub-nosed monkeys (Rhinopithecus roxellana). These species communicate both vocally and visually within family units and troops. They produce a variety of vocalizations for different purposes, including whines, shrills, group choruses, grunts, moans, sighs, barks, and alarm calls. Eighteen distinct call types have been identified among golden snub-nosed monkeys and four call types have been identified among Yunnan snub-nosed monkeys. Golden snub-nosed monkeys produce soft “hoo” calls to find each other if separated, soft “huu chhhk” calls while they are travelling, louder “huu chhhk” calls if they sense a threat, and quick “chit” calls when fleeing an area. Despite their use of vocalizations throughout the day, Yunnan snub-nosed monkeys have been observed to remain silent when approaching their resting areas, which likely serves as an anti-predator defense. Snub-nosed monkey species also communicate using visual cues. Males and females vary in color and males often have striking pelage and genitalia coloration. Snub-nosed monkeys communicate socially by curling and uncurling their lips, baring their teeth, adopting quadrupedal stances, raising their hackles, opening or closing their mouths, and maintaining eye contact. These behaviors may communicate aggression, playfulness, sexual receptivity, among other psychological states. Although they rely heavily on visual and acoustic cues for communication and perception, snub-nosed monkeys likely also communicate using physical and olfactory stimuli. For example, they participate in allogrooming as a means of strengthening social bonds and they likely release pheromones that play a role in intraspecific communication. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Harding and Han, 2018; Starr, 2022)

• Communication Channels
• visual
• tactile
• acoustic
• chemical

• Other Communication Modes
• duets
• choruses
• pheromones

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

Snub-nosed monkeys are omnivorous, but most of their diet consists of plant matter and fungi. They have sacculated stomachs, which help them digest leaves and carbohydrates found in toxic lichens.

Snub-nosed monkeys are largely folivorous, but are opportunistic foragers, taking advantage of whatever nutrient-dense herbivorous foods are available. In spring, when food diversity is highest, they eat grasses, mosses, fruits, flowers, nuts, leaf buds, and nectar. Later in summer and fall, snub-nosed monkeys mostly eat pine needles and young leaves of deciduous plants, which have lower toxin concentrations than mature leaves. Throughout the year, snub-nosed monkeys also feed on invertebrates as a source of protein to supplement their diets. Bamboo leaves and shoots are an especially abundant food source year-round for some species, depending on their geographic location. Snub-nosed monkeys build fat stores prior to winter, which makes fat-rich food sources like nuts and seeds an important part of their diet in summer and fall. In the winter, snub-nosed monkeys living in montane environments are often limited to consuming bark, pine needles, lichens, and snow. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Geissman, et al., 2020; Long, et al., 2020; Long, et al., 2022; Quyet, et al., 2020; Starr, 2022; Yongcheng and Richardson, 2021)

• Primary Diet
• carnivore
  • insectivore
  • eats non-insect arthropods
• herbivore
  • folivore
  • frugivore
  • granivore
  • lignivore
  • nectarivore
• omnivore

Predation

Snub-nosed monkeys serve as prey for a number of diurnal raptors and large mammals. Specific predator species vary depending on geographic location, but include northern goshawks (Accipiter gentilis), golden eagles (Aquila chrysaetos), gray wolves (Canis lupus), leopards (Panthera pardus), tigers (Panthera tigris), and various buzzards (genus Buteo).

Snub-nosed monkeys have several physical, social, and behavioral adaptations to deter or avoid predation. Snub-nosed monkeys have large canines, which are useful for threat displays and for self-defense, although their teeth likely play a larger role in intraspecific competition. Males are also larger than females and are responsible for defending their social groups from predators.

Snub-nosed monkeys are afforded some protection from predators because they live in social groups. Group size varies largely, with some consisting of small family units and other groups, called bands, having as many as 600 individuals. Social groups move and forage together, and alert group members of danger using vocalizations and body language. In large social groups, like troops and bands, females and juveniles travel together in the center of the group and dominant males travel at the front and rear of the group. If a predator is present, males will work together to ward it off using aggressive displays and vocalizations. Troops will travel between feeding sites together, moving to an average of two sites per day.

Snub-nosed monkeys also exhibit anti-predator behaviors that help them avoid detection. For example, social groups return to their resting sites around dusk and typically cease vocal communication upon reaching the area. Yunnan snub-nosed monkeys (Rhinopithecus bieti) retire to specific "sleeping trees" and individuals in a social group enter the tree in a particular order: females with infants enter first, other females enter second, juvenile males enter third, and the dominant male enters last. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Starr, 2022)

• Known Predators

  • Northern goshawks (Accipiter gentilis)
  • Golden eagles (Aquila chrysaetos)
  • Grey wolves (Canis lupus)
  • Leopards (Panthera pardus)
  • Tigers (Panthera tigris)
  • Buzzards (genus Buteo)

Ecosystem Roles

Snub-nosed monkeys are important seed dispersers for various native plant species. They eat seeds and nuts directly, or as a biproduct of frugivory. They may scatter seeds in the immediate area where they are feeding, but will also carry seeds in their digestive tract and scatter them far away when they defecate. It is likely that snub-nosed monkeys also play an important role in lichen reproduction and dispersal. Many snub-nosed monkey species rely on lichen as primary food source in winter. As snub-nosed monkeys eat lichen, they scatter bits of broken lichen around the area, which can asexually reproduce and grow on new surfaces. Furthermore, as snub-nosed monkeys disturb lichen, their fur catches spores from the fungi in lichen, and may disperse these spores to new areas. Snub-nosed monkeys may similarly disperse spores from pteridophyte plants, such as mosses, which supplement the diets of many snub-nosed monkey species throughout the year. During warmer seasons, snub-nosed monkeys opportunistically feed on flower nectar, which means they serve a minor ecosystem role as plant pollinators.

Although snub-nosed monkeys are largely herbivorous, they are also insectivorous and thus play a role in controlling insect populations. Snub-nosed monkeys also serve as prey for diurnal raptors and carnivorous mammals.

Snub-nosed monkeys serve as hosts for a number of parasites, notably roundworms (phylum Nematoda) and fleas (order Siphonaptera). One whipworm species, Trichuris rhinopithecus, and one subspecies of carnivore flea Vermipsylla parallela rhinopitheca, parasitize snub-nosed monkeys exclusively. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Geissman, et al., 2020; Harding and Han, 2018; Long, et al., 2020; Long, et al., 2022; Quyet, et al., 2020; Starr, 2022; Yongcheng and Richardson, 2021)

• Ecosystem Impact
• disperses seeds
• pollinates
• creates habitat

Economic Importance for Humans: Positive

Due to the isolation of snub-nosed monkeys to montane forest habitats, they do not have any regular economic importance for humans. However, snub-nosed monkeys are used as part of traditional medicinal practices, and are victims of illegal poaching practices and the illegal pet trade market. Golden snub-nosed monkeys (Rhinopithecus roxellana) are trapped illegally for tourist photoshoots and hunted illegally for bushmeat. Snub-nosed monkey species also indirectly benefit forestry industries due to their roles as seed dispersers and pollinators.

Snub-nosed monkeys are occasionally kept in zoos and primate conservancies around the world. Because they are a charismatic primate species, their presence on media platforms can help draw public funding to conservation organizations and local communities. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Geissmann, et al., 2011; Long, et al., 2020; Long, et al., 2022; Quyet, et al., 2020; Starr, 2022; Yongcheng and Richardson, 2021)

• Positive Impacts
• pet trade
• food
• body parts are source of valuable material
• ecotourism
• source of medicine or drug

Economic Importance for Humans: Negative

Snub-nosed monkeys do not regularly cause any negative economic impacts, as they live in isolated montane environments. However, as urbanization continues to encroach on these habitats, the likelihood of zoonotic disease transmission or other conflicts with human populations will likely increase. In 2022, videos of golden snub-nosed monkeys (Rhinopithecus roxellana) being hand-fed in Chinese villages circulated around the internet. Close interactions like these increase the chance of disease transmission and reduce the natural aversion that many animals have to interacting with humans. Snub-nosed monkeys have sharp teeth and powerful jaws, and thus can cause serious injury to humans if they are kept as pets or approached too closely. (Geissmann, et al., 2011; Long, et al., 2020; Long, et al., 2022; Quyet, et al., 2020; Yongcheng and Richardson, 2021)

• Negative Impacts
• injures humans
  • bites or stings
  • causes disease in humans
  • carries human disease

Conservation Status

Of the five currently valid snub-nosed monkey species, three are considered critically endangered on the IUCN Red List: Tonkin snub-nosed monkeys (Rhinopithecus avunculus), gray snub-nosed monkeys (Rhinopithecus brelichi), and Myanmar snub-nosed monkeys (Rhinopithecus strykeri). The other two species are listed as endangered: Yunnan snub-nosed monkeys (Rhinopithecus bieti) and golden snub-nosed monkeys (Rhinopithecus roxellana).

Snub-nosed monkeys are impacted heavily by habitat conversion and fragmentation due to human development. Anthropogenic activities that impact snub-nosed monkeys include timber harvesting, agriculture, and urbanization, as well as the construction of roads, railroads, mines, utility lines, hydropower dams, and recreational developments. Other threats to snub-nosed monkeys include illegal poaching and trapping, pesticide applications, and the effects of climate change. In particular, the largest non-habitat-related human impact on snub-nosed monkeys is trapping bycatch. Snub-nosed monkeys are frequently trapped by accident in snares and bear traps set for other more common bush meat and game species.

All snub-nosed monkeys are protected under Appendix I of CITES, which strictly regulates trade of endangered animals. Several species are also explicitly protected by national governments. Many snub-nosed monkey species have geographic ranges that include protected public lands, such as national parks, which ensure protected habitat with limited development.

Current conservation efforts directed towards snub-nosed monkeys include captive breeding programs in China. However, the gene pools of captive individuals are limited, and many attempts at captive breeding have been unsuccessful. Public education and academic research play important roles in snub-nosed monkey conservation. Scientists from local and international institutions perform research on snub-nosed monkeys. This research improves our understanding of their life history, population sizes, and the types of management strategies that are effective. Information collected by researchers can be made publicly available and shared with local communities, encouraging awareness of the conservation needs of snub-nosed monkeys. (Abrams, 2018a; Abrams, 2018b; Davi, 2018; Downey, 2018; Geissmann, et al., 2011; Long, et al., 2020; Long, et al., 2022; Nuchel, et al., 2018; Quyet, et al., 2020; Starr, 2022; Yongcheng and Richardson, 2021)

• IUCN Red List [Link]

  Not Evaluated

Other Comments

Much of the information regarding snub-nosed monkeys is comes from research on golden snub-nosed monkeys (Rhinopithecus roxellana). It is important to note that gray snub-nosed monkeys (Rhinopithecus brelichi) and Myanmar snub-nosed monkeys (Rhinopithecus strykeri) are especially understudied.

Contributors

Daniel Rice (author), Colorado State University, Galen Burrell (editor), Special Projects.

References

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