Black snub-nosed monkeys (Rhinopithecus bieti) are endemic and confined to the Hengduan Mountains, located in southwest China and Tibet. The southernmost population was thought to be in the Yunlong Provincial Nature Reserve in Mt.Longma, but the distribution has shifted south about 40 km after the discovery of a group at the Tianchi Provincial Nature Reserve. The distribution is approximately 400 km in length and 100 km in width. (Harding and Han, 2018; Long, et al., 1994)
Black snub-nosed monkeys are found in coniferous or mixed coniferous broad leaved forests and are one of the most northerly primates with one of the highest elevation ranges - from 2,625 to 4,600 m above sea level. Some groups have been seen going above 4,700 m when foraging. These monkeys live in the mountain forests all year round. (Harding and Han, 2018)
As one of the largest members of the Colobinae subfamily, black snub-nosed monkey males have head and body lengths ranging from 740 to 830 mm and tail lengths ranging from 510 to 720 mm. They are the most sexually dimorphic of snub-nosed monkeys, as males are 50% larger than females. Males weigh around 15 to 17 kg while females are 6.5 to 10 kg. The features they have in common with other snub-nosed monkeys are characteristically thick lips and concaved nostrils. However, black snub-nosed monkeys are the only black and white snub-nosed monkeys with long hair.
Males have distinguishable dark crowns of hair that droop forward, forming a crest around 97 to 120 mm long. Their faces are white with black noses and pink lips. The fur on their arms, backs, and lower legs are black, with white tufts at the elbows. A whitish-gray color fur covers their cheeks all the way down their ventral sides, covering their necks, thighs, and abdomens. The hairs around their pelvic areas and thighs are very elongated forming 200 to 210 mm long fringes.
Compared to males, black snub-nosed monkey females and juveniles are not as black and have shorter hairs on their backs, crowns, and thighs. Infants are white and yellowish before they turn the lighter black color seen in juveniles. (Harding and Han, 2018; Huang, et al., 2012)
Black snub-nosed monkeys form large groups, or bands. Within a band are units that are often one-male units (OMUs) comprised of one male with multiple females and their offspring. The adult sex ratio is skewed towards females with a 3.1:1 ratio. The relationship among OMUs are usually neutral and when aggression does occur, it is often among the adult males defending their mates.
During the mating season, females initiate mating through prostration, which involves lying stretched out on the ground and repeatedly glancing at males. They sometimes also jump to get the attention of males and then present to males or sit down and move their head up and down while pausing to look at males. If solicitation is ignored, females alternate between the three behaviors in a solicitation cycle. Male solicitation involves gazing at females and baring their teeth and grunting. Ejaculatory copulation was observed less than two times a day and required multiple mounts. (Cui and Xiao, 2004; Harding and Han, 2018)
In the wild and in captivity, sexual maturity occurs at 4 to 5 years for females and 6 to 7 years for males. Mating in black snub-nosed monkeys occurs year round with the height of the breeding season in August and September, coinciding with the period of highest temperatures and highest quality food availability.
With a gestation period of 6 to 7 months in wild populations and a period of 195 to 204 days in captive individuals, the birth season starts in March and ends in April. Usually, one offspring is born. Females do not start weaning infants until they are more than 6 months of age. This means that females that are weaning young will not breed the same year their child is born. In addition, evidence shows that the ratio of infants to adult females is 1:2.3, suggesting that there is an inter-birth interval of about two years. (Cui, et al., 2006; Cui, et al., 2008; Huang, et al., 2012)
Black snub-nosed monkey infants less than 15 days old are carried only by their mothers. By three weeks of age, mothers allow adult and juvenile females in the same OMU to provide allomaternal care through grooming, transporting, and holding the infant. By 6 months of age, infants obtain most of their food by their own foraging efforts, but may still continue to nurse for an additional 6 to 14 months.
Allomaternal nursing occurs when a lactating female provides milk for the offspring of another female. This was once observed when an infant from one OMU infiltrated another OMU. The latter OMU was not hostile to the new infant with the dominant male even transporting the non-natal infant. The infant became fully integrated into the new unit and nursed from a lactating female. The birth mother never retrieved the infant.
Male allocare includes carrying infants that are not theirs when traveling. This protects infants against predators or other adult males. Male allocare peaks during energetically stressful seasons, when food is scarce. It dies down in the summer, after the birth season, when female allocare increases. (Harding and Han, 2018; Ren, et al., 2012a)
There is currently no information on the lifespan of black snub-nosed monkeys both in the wild and in captivity. However, golden snub-nosed monkeys (Rhinopithecus roxellana) of the same genus have a lifespan of 23 years in captivity, but no data is available for this species in the wild. (Gron, 2007)
The bands that black snub-nosed monkeys form can include up to 480 individuals that are divided into 11 to 26 units of 3 to 17 individuals. These units are mostly OMUs, along with one or more all-male units (AMUs). Multi-male with multi-female units are rare and do not have more than two adult males. Most aggression between OMUs is due to males defending their mates. However, findings suggest that females within OMUs compete for access to the male in the unit and that female mating success is low in larger groups.
Black snub-nosed monkeys are social animals that display fission-fusion behavior, in which bands split into smaller units in response to changes in food availability, due to seasonality changes. Large bands feed as social units throughout the year, but split up at the end of a birth season, when new mothers are lactating and high quality food is in season. Splitting up and subgrouping occurs for efficient exploitation of limiting resources.
Black snub-nosed monkey bands travel in single-file to new sleeping and feeding sites. They travel both daily and seasonally in response to environmental variables such as temperature, slope, and sunlight. They are considered semi-nomadic, since they do not remain in already foraged areas for long, spending several hours before seeking new places to forage or sleep. Sleeping sites are often in tall trees on steep slopes, with sun exposure and protection from wind. Groups are often willing to travel long distances to sleeping sites if suitable ones are not near foraging areas. This suggests consideration of both energetic and antipredator potential. The adult male in an OMU sleeps alone, while adult females, infants, and juveniles participate in group huddling during the night. (Harding and Han, 2018; Kirkpatrick and Grueter, 2010; Ren, et al., 2012b)
Black snub-nosed monkeys travel farther in warmer months. In a given year, the home range of bands can be 16 to 40 km2.
Black snub-nosed monkey groups are relatively quiet, mainly communicating using eye contact and gestures when resting and foraging. In conflicts and stressful situations, males use a distinct, loud bray, and flash their canines. When predators are near, adults emit loud alarm calls. (Harding and Han, 2018)
Black snub-nosed monkeys primarily eat immature leaves of flowering trees in the spring, fruit in summer and fall, and lichens in the winter. Lichens are also a fallback food in seasons when leaves and fruits of flowering trees are unavailable. Black snub-nosed monkeys are primarily arboreal, but have been observed digging up mushrooms and tubers and eating rodents and bird eggs. (Harding and Han, 2018; Kirkpatrick and Grueter, 2010)
Only aerial predators such as eagles (genus Aquila) and buzzards (genus Buteo) have been reported to prey on black snub-nosed monkeys. These predators employ a circle-and-wait strategy. When they detect predators, black snub-nosed monkeys drop out of sight to the lower canopy. (Cui, 2003; Harding and Han, 2018)
Black snub-nosed monkeys play a part in the local food web, since they are prey for avian carnivores and are likely to impact vegetation through herbivory and seed dispersal.
Black snub-nosed monkeys were once hunted for food, medicine, and money. (Harding and Han, 2018)
There are no known adverse effects of black snub-nosed monkeys on humans.
Black snub-nosed monkeys are listed by IUCN and the U.S. endangered species act as endangered. CITES has all Rhinopithecus species on Appendix 1. The major threat to black snub-nosed monkeys is human activities, such as logging and hunting. They are often caught accidentally by snares meant for ungulates. The national government in China established two protected areas for black snub-nosed monkeys: the Hongla Xue Shan Mountain National Nature Reserve in Tibet and the Baimaxueshan National Nature Reserve in Yunnan. Presently, the approximation seems to total 2,500 individuals known in the wild. (Harding and Han, 2018; Xiang, et al., 2013)
Across their range, black snub-nosed monkeys are faced with challenges, dealing with hypothermia, hypoxia, and locating calorie-rich food during cold and high elevation winters. There is evidence in their genome for the selection of several genes that facilitate an adaptive response to hypoxia. This is likely an adaptation to the high elevations at which black snub-nosed monkeys live. (Zhou, et al., 2016)
Xin Deng (author), University of Washington, Laura Prugh (editor), University of Washington, Galen Burrell (editor), Special Projects.
uses sound to communicate
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.
Referring to an animal that lives in trees; tree-climbing.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
helpers provide assistance in raising young that are not their own
a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
an animal that mainly eats leaves.
A substance that provides both nutrients and energy to a living thing.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
an animal that mainly eats fruit
An animal that eats mainly plants or parts of plants.
parental care is carried out by males
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
generally wanders from place to place, usually within a well-defined range.
found in the oriental region of the world. In other words, India and southeast Asia.
having more than one female as a mate at one time
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
Living on the ground.
uses sight to communicate
breeding takes place throughout the year
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