The family Cercopithecidae, or old world monkeys, includes leaf monkeys and langurs in the subfamily Colobinae. The subfamily has a wide geographical distribution throughout Asia and Africa. Trachypithecus francoisi, however, is found only in southern Guangxi province in China, northern Vietnam, and west-central Laos.
Biogeographic Regions: oriental (Native )
- Helin, S., N. Ohtaishi, L. Houji. 1999. The Mammalian of China. Beijing: China Forestry Publishing House.
- Nowak, R. 1997. "Walker's Mammals of the World Online 5.1" (On-line). Accessed October 12, 2004 at http://www.press.jhu.edu/books/walkers_mammals_of_the_world/primates/primates.cercopithecidae.trachypithecus.html.
- Tate, G. 1947. Mammals of Eastern Asia. New York: The Macmillan Company.
China (Kwangsi), Indochina
Though males of the species are slightly larger than females, T. francoisi are approximately two feet tall and weigh between 4 and 14 kg. Lengths between 400 and 760 mm are reported.
Pelage varies from uniformly brown, black, or dark gray with a white stripe running from the corner of the mouth to the ear. White is also present in a crest above the eyes, resembling eyebrows, a feature which distinguishes them from species in the genus Presbytis. Young are golden yellow with a black tail, another feature that distinguishes these monkeys from the black young of Presbytis.
These leaf monkeys have small heads and lack cheek pouches. The tail is long, straight, and black with a white tip. Forelegs are much shorter than hind legs with hairless hands and feet that allow easy grasping of branches. Thumbs are well-developed, opposable, and significantly shorter than the thumbs of Presbytis.
This species has not been studied extensively in captivity and information regarding metabolic rate is unavailable.
Range mass: 4.3 to 14 kg.
Range length: 400 to 760 mm.
Sexual Dimorphism: male larger
Other Physical Features: endothermic ; bilateral symmetry
An arboreal species, T. francoisi inhabits densely forested and limestone areas of tropical lowlands and forest valleys. Information regarding exact elevations occupied by these animals is unavailable.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: forest ; rainforest
- Glover, A. 1938. The Mammals of China and Mongolia. New york: American Museum of Natural History.
Habitat and Ecology
Like other Trachypithecus, T. francoisi is mostly folivorous, with the remainder of its diet consisting of shoots, fruits, flowers, and bark. Males and females reach sexual maturity in five and four years, respectively. Litter size is usually one, and birth intervals for this species are recorded at about 20 months (Nadler et al. 2003).
Trachypithecus francoisi feeds primarily on foliage, especially mature leaves, as well as some fruit and occasional insects. This low protein, high fiber diet requires a modified digestive system. The stomachs of monkeys in the Colobinae subfamily are large and multi-chambered. The forestomach hosts bacteria with cellulose-digesting abilities, allowing these mammals to process plant fibers.
Animal Foods: insects
Plant Foods: leaves; fruit
Primary Diet: herbivore (Folivore )
- Becher, F., J. Nijboer, J. van der Kuilen, A. Beynen. 2001. Chemical analysis and consistency of faeces produced by captive monkeys (Francois langurs, Trachypithecus francoisi) fed supplemental fibre. Veterinary Quarterly, 23/2: 76-80.
- Davies, A. 1994. Colobine populations. Pp. 285-310 in J Oates, ed. Colobine Monkeys: Their Ecology Behavior and Evolution. Cambridge: Cambridge University Press.
The diet of primarily mature leaves is unique to T. francoisi, as other leaf eating monkeys prefer young leaves. Other than this impact on forest foliage, little is known about the role of these animals in the ecosystem.
Little is known regarding adaptations to avoid predation, antipredator behaviors, or life history modifications as they might relate to predation of T. francoisi. However, a 1994 study suggests that species in this family are not limited by predation, except for being hunted by humans.
- Isbell, L. 1994. Predation on primates: ecological patterns and evolutionary consequences. Evolutionary Anthropology, 3: 151-154.
Life History and Behavior
Vocalization and visual displays have been observed in other members of the genus; however, little is know about the communication of T. francoisi. It is reasonable for us to assume that, as in other primates, visual, tactical, accoustic, and chemical communication are all used by these monkeys.
Communication Channels: visual ; tactile ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical
It has been recorded that this species does not survive well in captivity, but specific information is otherwise unavailable.
Status: captivity: 26.3 (high) years.
- Collins, L., M. Roberts. 1978. Arboreal folivores in captivity- maintenance of a delicate minority. Pp. 5-12 in G Montgomery, ed. The Ecology of Arboreal Folivores. Washington: Smithsonian Institute.
Lifespan, longevity, and ageing
It is common among colobines for females to initiate sexual behavior, and T. francoisi is no exception. Female proceptive behavior has been documented in the species, though specific information about this behavior is not available.
Trachypithecus francoisi is somewhat of an exception among other species in the family in that the social structure involves primarily one-male groups, in which one male mates with multiple females. Though it has not yet been observed in this species, other species in the genus are known to form all-male groups which occasionally attack one-male groups in order to oust the dominant male and take his place with the females.
Mating System: polygynous ; cooperative breeder
Mating occurs throughout the year, peaking in autumn and winter. The frequency of breeding is unknown. The estrous cycle is 24 days and gestation lasts 6 to 7 months. A female delivers a single offspring once annually. The young are born fully furred and are fairly active. Animals become sexually mature after 4 or 5 years. The species has not been widely studied and the time to weaning and independence of the young is unknown.
Breeding interval: Females are capable of producing young annually.
Breeding season: Trachypithecus francoisi mates year-round, although breeding peaks in autumn and winter
Range number of offspring: 1 to 2.
Average number of offspring: 1.
Range gestation period: 6 to 7 months.
Range age at sexual or reproductive maturity (female): 4 to 5 years.
Range age at sexual or reproductive maturity (male): 4 to 5 years.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous
Average birth mass: 457 g.
Female alloparental care of T. francoisi young has been documented and is a common trait among other Asian colobine species. It is hypothesized that alloparental care provides time and freedom for mothers to forage, improves parenting skills of the alloparent, and ensures the social integration of new infants to the group increasing the likelihood of adoption if the mother is killed. Additionally, it has been suggested that the infrequent but sometimes abusive handling of new infants by the alloparent reduces resource competition for the alloparents’ own offspring.
Other aspects of parental investment are unknown. However, in most primates with similar social structures, females provide the bulk of parental care. They groom, carry, and protect their young. However, males may also play some role in carrying, provisioning and protecting young. The most important parental role of males may be to protect young from potentially infanticidal rival males.
Parental Investment: altricial ; precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female); pre-independence (Provisioning: Female, Protecting: Male, Female); post-independence association with parents; extended period of juvenile learning
- Nowak, R. 1997. "Walker's Mammals of the World Online 5.1" (On-line). Accessed October 12, 2004 at http://www.press.jhu.edu/books/walkers_mammals_of_the_world/primates/primates.cercopithecidae.trachypithecus.html.
- Yeager, C., K. Kool. 2000. Behavioral ecology of Asian colobines. Pp. 496-521 in P Whitehead, J Clifford, eds. Old World Monkeys. Cambridge: Cambridge University Press.
Molecular Biology and Genetics
Statistics of barcoding coverage: Trachypithecus francoisi
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
Trachypithecus francoisi is are listed as Endangered by the US Fish and Wildlife service, and the IUCN classifies the species as Vulnerable, with its status dependent on ongoing conservation efforts. CITES lists the species in Appendix I. The subspecies T. f. delacouri of central Viet Nam may be the most endangered monkey in Asia with fewer than 250 individuals alive. It has also been reported that T. f. leucocephalus in southeastern China has a population of only about 400, a result of hunting the monkey for its believed medicinal value. Populations of most other species of Trachypithecus are also declining due to loss of habitat.
Threats to the species include habitat loss to the expansion of agriculture, fuelwood harvesting, warfare, logging, and hunting.
US Federal List: endangered
CITES: appendix i
IUCN Red List of Threatened Species: endangered
IUCN Red List Assessment
Red List Category
Red List Criteria
Date Listed: 10/19/1976
Lead Region: Foreign (Region 10)
Where Listed: Entire
Population location: Entire
Listing status: E
For most current information and documents related to the conservation status and management of Trachypithecus francoisi, see its USFWS Species Profile
In Viet Nam it occurs in several protected areas, including two national parks. At least two protected areas have been established specifically for this species: Sinh Long-Lung Nhoi Species and Habitat Conservation Area (Tuyen Quang Province) and Nam Xuan Lac Species and Habitat Conservation Area (Bac Kan Province).
In China it is found in 21 protected areas, three of which are national level (Lou et al. in litt.) Also, it is legally protected from hunting, though it faces additional threats there from unrestricted resource extraction and habitat disturbance (Hu et al. 2004). There is a successful captive-breeding program for this species now underway in China in Wushou (Nadler et al. 2003).
Relevance to Humans and Ecosystems
Negative economic impact to humans, other than the possibility of a retrovirus transmittal, cannot be inferred from the available information.
Negative Impacts: injures humans (carries human disease)
Trachypithecus francoisi has been used in researching retroviruses that infect a variety of nonhuman primates and can be transmitted to exposed humans. The species is also hunted for its believed medicinal value.
Positive Impacts: source of medicine or drug ; research and education
- Hussain, A., V. Shanmugam, V. Bhullar, B. Beer, D. Vallet. 2003. Screening for simian foamy virus infection by using a combined antigen Western blot assay: evidence for a wide distribution among Old World primates and identification of four new divergent viruses. Virology, 306/2: 248-257.
- Massicot, P. 2004. "Animal Info- Francois' Leaf Monkey" (On-line). Accessed October 12, 2004 at http://www.animalinfo.org/species/primate/tracfran.htm.
François' langur (Trachypithecus francoisi), also known as Francois' leaf monkey, Tonkin leaf monkey, or white side-burned black langur is a species of lutung and the type species of its species group. It is the least studied of the species belonging to the Colobinae subfamily.
The species is distributed from Southwestern China to northeastern Vietnam. The total number of wild individuals is unknown, but there are believed to be less than 500 left in Vietnam and 1,400–1,650 in China. There are about 60 langurs in captivity in North American zoos. The species is named after Auguste François (1857–1935) who was the French Consul at Lungchow in southern China.
François' langur is a medium sized primate with black silky hair. It has very distinct white sideburns that grow down from its ears to the corners of its cheeks. A morphological specialization of François' langur is its complex stomach, made up of four separate chambers. This is a necessary adaptation for the digestion of its folivorous diet.
This species shows sexual dimorphism in its size. Males have a head-body length of 55–64 cm (22–25 in), while females are only 47–59 cm (19–23 in) in length. Males likewise have longer tails of 82–96 cm (32–38 in) compared to the 74–89 cm (29–35 in) for females. Males are significantly heavier than females, weighing 6.5–7.2 kg (14–16 lb) compared to 5.5–5.9 kg (12–13 lb) for females. Infants weigh 0.45–0.50 kg (16–18 oz) at birth.
François' langur has large salivary glands to begin the digestion of tough leaf fibers. A more notable evolutionary adaptation seen in this langur is the sacculated stomach with two chambers. In the upper chamber, bacteria help to continue the breakdown of fibers started by the saliva. The upper chamber has a relatively normal pH, to create favorable conditions for bacterial growth. The lower chamber is similar to that of other mammals, in that it contains the acids that finish the breakdown of food components.
François' langur is diurnal and spends most of the day resting and foraging. One study investigated time distribution across activities in a disturbed environment, showing resting 35.41%, foraging 31.67%, traveling 14.44%, huddling 9.61%, playing 8.54%, and grooming 0.33%. Traveling, playing, grooming and huddling are more dependent on the season. Interestingly it has been found that grooming occurs in all seasons but spring. François' langur spends a greater part of its day travelling during the winter (20.12%) and huddling in the spring (14.62%).
François' langur lives in groups of four to twenty-seven langurs, but will usually be found in groups of around twelve. It lives in a matriarchal society where the females lead the group. Within the society, the females perform alloparenting, sharing parenting responsibilities with one another, and are philopatric to the group. Males within the group take no part in the raising of the young, the young males will leave the group before reaching sexual maturity. Young langurs are nursed for up to two years before being weaned, and once weaned the relationship amongst the relatives becomes that of any other member of a given group.
Over 50% of François' langur's diet is made up of leaves. It will also consume fruits (17.2%), seeds (14.2%), flowers, stems, roots, bark and occasionally minerals and insects from rock surfaces and cliffs. This langur consumes its favorite food, young leaves, at the highest rate during the dry season, April through September; between October and March when young leaves are less common, the langur supplements its diet with seeds, petioles, and stems.
François' langur is selective in its diet, in Nonggang Nature Reserve, China, it primarily eats the young leaves of ten different species of plant, only two of which are common within the reserve. Its diet includes Pithecellobium clypearia, Ficus nervosa, Garcinia pauncinervis, Sinosideroxylon pedunculatum, F. microcarpa, Miliusa chunni, Securidaca inappendiculata, Bauhinia sp., and Canthium dicoccum. Though these are the preferred plant species, it will still consume other plant species opportunistically. Another study on François' langur in a fragmented habitat found that it preferred on just four plant species: litse, Litsea glutinosa; seatung, Pittosporum glabratum; Cipadessa cinerascens; and Chinese desmos, Desmos chinensis. The study showed that the langur spent 61.6% of its feeding time on these four plant species, and 38.4% of its time on 36 other known species.
Habitat and distribution
The preferred habitat of François' langur is a karst topography; limestone cliffs and caves of tropical and subtropical zones. By living on these limestone cliffs, the langur is at an advantage when it comes to sleeping arrangements. It sleeps either on ledges or in caves, with its preference being in the cave. François' langur has also been known to find sleeping sights in areas where the terrain is above 60 °F (16 °C), within evergreen forests. By living and sleeping in these limestone caves and cliffs, far from flat land, the langur has greatly reduced its rate of predation. It exhibits cryptic behavior and becomes very vigilant upon entry to the cave for final resting as a tactic to avoid any predators. In addition to this it also demonstrates a loud call to declare its territorial spacing. François' langur will also choose its sleeping habitat depending upon foraging availability. It will choose sleeping sites that are close to potential foraging sites, to maximize energy and reduce travel costs. It is important to note that sleeping sites are not located in the heart of foraging sites, but are within reasonable proximity, as the preferred nesting and foraging sites do not completely line up with one another. When it does go to forage, it tends to travel along the same route and returns to the same sleeping site consecutive nights to avoid predation. François' langur has been known to have approximately 6-10 regularly used sleeping sites that are used at various points throughout the year as water and food resources fluctuate.
François' langur has a restricted range of areas in which it can inhabit. It is primarily found in Southwest China and northern Vietnam. The majority of scientific studies of François' langur in the wild take place in the Nonggang Nature Reserve and the Fusui Nature Reserve in Guangxi Province, China. The average home range size of this species is 19 hectares (230,000 sq yd) and its day range size is 341–577 square metres (3,670–6,210 sq ft). In general, the low quality of its folivorous diet leads to nutritional stress, a smaller home range size and reduced daily travel time. The largest group of langurs reported numbered 500-600 individuals, and was found in the Mayanghe National Nature Reserve. The average group size is approximately 4-27. The Fusui Nature Reserve reported in 2009 that François' langur population had declined 73% in the previous 5 years, thus lessening their distribution even more. Recent census numbers have concluded that it is now limited to 14 localities in 10 different counties.
The population of François' langur has been on a steady decline for the past 30 years. Of the many factors threatening the survival of François' langur today, hunting has had one of the largest impacts. In Nonggang, where François' langur is most prevalent, the natives believe that the langur has medicinal values, and have hunted them to make wine out of their bones, which they believe could cure fatigue and rheumatism. In Guangxi province there has been an estimated 90% decline in numbers since the 1980s, a 2002-2003 survey found 307 individuals in 14 populations remained. In 1983, the estimated population of François' langur was 4,000-5,000. In the 1970s, hunting records recorded more than 1,400 langurs killed and in the 1980s more than 1,500 langurs were killed.
Another threat to François' langur is the destruction of its habitat. The langur lives on limestone cliffs and when farmers look to cultivate their land they will light fires on the lower slopes. Limestone is particularly susceptible to fire; therefore this practice not only destroys its habitats but also causes major food shortages for the langur because its diet is primarily folivorous. The primary predators of François' langur are both terrestrial and aerial. The clouded leopard is a potential predator to the langur but the clouded leopard's numbers are so low that they are not its greatest threat. Aerial predators such as the crested serpent eagle and the mountain hawk-eagle are a greater threat to François' langurs of Nonggang, especially to their young.
The actions being taken towards the conservation of this species and its habitat is still minimal. Its current population size is less than 2,500 individuals. A plan to protect the forest and ban hunting, called the Conservation Action Plan, was drafted in 1996 but has still yet to be implemented. In order to protect the langur, not only does protection from hunting need to be implemented but its habitats must be protected as well. In 2003, the National Forestry Bureau acknowledged the rapid decline in François' langur and agreed to increase law enforcement in this area to help protect the langur from hunters. In addition, the Asia Developmental Bank has begun helping the residents that live in close proximity to the habitats of the langur build biogas facilities to reduce the fuel wood collection and thus possibly reduce the number of fires. And finally, a current project is underway by the Global Environmental facility to protect the Nonggang National and Dmingshan Natural Reserves and the langurs living within.
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- The Eponym Dictionary of Mammals - Page 141 Bo Beolens, Michael Watkins, Michael Grayson - 2009 "François' Leaf Monkey Trachypithecus francoisi Pousargues, 1898 [Alt. François' Langur] Auguste François (1857–1935) was the French Consul at Lungchow in southern China, where he was the first person to bring this monkey to the ..."
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