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)
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.
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
It has been recorded that this species does not survive well in captivity, but specific information is otherwise unavailable.
Range lifespan
Status: captivity: 26.3 (high) years.
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
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 )
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 )
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.
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
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
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
Common names for the species include: capped leaf monkeys, langurs, leaf monkeys, brow-ridged langurs, and black leaf monkeys.
Trachypithecus francoisi was first noticed by M. Francois, the French Consul at Lungchow, Kwangsi, China, who found specimens on cliffs along the Longkiang River. He described flocks of small black monkeys with long tails and black heads. The species was first officially described by Pousargues in 1898 from specimens collected in Longzhou, southern Guangxi Province in China.
Trachypithecus was recognized as a separate genus by Eudey in 1987, but occasionally it is still considered a subgenus or synonym of Presbytis or of Semnopithecus. There are nine other species recognized in the genus: Trachypithecus vetulus, T. johnii, T. geei, T. pileatus, T. phayrei, T. cristatus, T. auratus, and T. obscurus. There is some debate over whether Trachypithecus leucoscephalus is a subspecies of T. francoisi or a distinct species. Recent DNA research suggests that it may in fact be distinct.
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
François' langur (Trachypithecus francoisi), also known as Francois' leaf monkey, the Tonkin leaf monkey, or the white side-burned black langur[3] is a species of lutung and the type species of its species group. It is one of the least studied of the species belonging to the Colobinae subfamily.[4]
The species is distributed from Southwestern China to northeastern Vietnam. The total number of wild individuals is unknown, but fewer than 500 are believed to be left in Vietnam and 1,400–1,650 in China.[2] About 60 langurs are 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.[5]
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.[3] 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.[4]
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.[3]
Infants are born with bright orange coloured fur, which fades to black throughout the period of infancy lasting several months. It is not known why their coats are so conspicuous, but current hypotheses suggest it may elicit attention, protection and caregiving by adults.[6]
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.[3]
François' langur is diurnal and spends most of the day resting and foraging.[7] 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%.[7] Traveling, playing, grooming and huddling are more dependent on the season.[8] Grooming has been found to occur in all seasons but spring.[7] François' langur spends a greater part of its day travelling during the winter (20.12%) and huddling in the spring (14.62%).[8]
François' langur lives in groups of 4 to 27 langurs, but will usually be found in groups around 12.[3][9] It lives in a matriarchal society where the females lead the group. Within the society, the females share parenting responsibilities with one another, and are philopatric to the group.[9] Males within the group take no part in the raising of the young, and the young males leave the group before reaching sexual maturity.[9] Young langurs are nursed 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.[3]
Over 50% of François' langur's diet is made up of leaves. It also consumes 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.[4]
François' langur is selective in its diet, in Nonggang Nature Reserve, China, it primarily eats the young leaves of 10 different species of plants, 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 still consumes other plant species opportunistically.[4] 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.[10]
The preferred habitat of François' langur is a karst topography; limestone cliffs and caves of tropical and subtropical zones.[11] 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.[12] François' langur has also been known to find sleeping sites in areas where the terrain is above 60 °F (16 °C), within evergreen forests.[13] By living and sleeping in these limestone caves and cliffs, far from flat land, the langur has greatly reduced its rate of predation.[13] It exhibits cryptic behavior and becomes very vigilant upon entry to the cave for final resting as a tactic to avoid any predators.[12] In addition, it demonstrates a loud call to declare its territorial spacing.[14] François' langur also chooses its sleeping habitat depending upon foraging availability. It chooses sleeping sites that are close to potential foraging sites, to conserve energy and reduce travel costs.[13] 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.[13] 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.[12] 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.[13]
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.[9] 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).[9] 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.[7] The average group size ranges from four to 27.[3] The Fusui Nature Reserve reported in 2009 that François' langur population had declined 73% in the previous five years, thus lessening their distribution even more.[9] Recent census numbers have concluded it is now limited to 14 localities in 10 different counties.[10]
The population of François' langur has been on a steady decline for the past 30 years. Of the many factors threatening their survival today, hunting has had one of the largest impacts.[11] In Nonggang, where it 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.[11] In Guangxi province, an estimated 90% decline in numbers has occurred since the 1980s; a 2002–2003 survey found 307 individuals in 14 populations remained.[11] 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 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 light fires on the lower slopes.[3] 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 foliage.[11] The primary predators of François' langur are both terrestrial and aerial.[12] The clouded leopard is a potential predator, but its numbers are low enough that it is not the langur's 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.[12]
Despite the extreme and continuing decline in the Francois' langur population, the actions being taken towards the conservation of this species and its habitat are still somewhat minimal. Its current population size is less than 2,500 individuals.[11] A plan to protect the forest and ban hunting, called the Conservation Action Plan, was drafted in 1996, but has yet to be implemented. To protect the langur, not only does protection from hunting need to be implemented, but its habitats must be protected as well.[3] 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 them from hunters.[11] In addition, the Asia Developmental Bank has begun helping the residents who live in close proximity to langur habitats build biogas facilities to reduce the fuel wood collection, thus possibly reducing the number of fires.[11] 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.[11]
François' langur (Trachypithecus francoisi), also known as Francois' leaf monkey, the Tonkin leaf monkey, or the white side-burned black langur is a species of lutung and the type species of its species group. It is one of 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 fewer than 500 are believed to be left in Vietnam and 1,400–1,650 in China. About 60 langurs are 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.
