Nomascus leucogenys
Creators: name: Russell A. Mittermeier
name: Anthony B. Rylands
name: Don E. Wilson
Publisher: name: Lynx Edicions
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Primates
Hylobatidae
Nomascus
Nomascus leucogenys

description: 16.
Northern White-cheeked Crested Gibbon
Nomascus leucogenys
French: Gibbon a joues blanches / German: Nordlicher Wei 3wangengibbon / Spanish: Gibén de mejillas blancas septentrional
Other common names: Northern White-cheeked Gibbon, White-cheeked Gibbon
Taxonomy. Hylobates leucogenys Ogilby, 1841,
Siam. Restricted by J. Fooden in 1987 to Laos, Muang Khi.
Two subspecies, leucogenys and siki, have been recognized in the past, but most authorities now treat these as separate species based on genetic and morphological evidence. In the past, there would have been contact zones with N. concolor in Yunnan, China, and they may still occur in north-western Laos, but whether there is sympatry or hybridization is not known. Monotypic.
Distribution. S China (extreme S Yunnan Province), N Laos, and NW Vietnam between the Mekong and Black rivers, to the S possibly limited by the Khading River in Laos and the Rao Nay River in Ha Tinh Province in Vietnam.
Descriptive notes. Head-body 47-525 cm (n = 5 males and 2 females); weight of males 6-4 kg (SD 0-9 kg, n = 5) and of females 6-6 kg (SD 0-6 kg, n = 5). Adult males and juveniles of both sexes of the Northern White-cheeked Crested Gibbon are black with white cheek-whiskers that form a narrow streak starting under the chin and reaching to the tops of the ears. Adult females are pale yellow to orange-yellow, with a black to brown crown streak and thin white face-ring that may or may not be complete. Hair in both sexesis long (40-70 mm) and rather coarse. The crown hair is erect and elongated in the middle, forming a high crown crest in the male but absentin the female.
Habitat. Tall primary and mature secondary tropical broadleaf evergreen and semievergreen forest and also high-elevation, mixed coniferous forests in Vietnam. Elevational distribution of the Northern White-cheeked Crested Gibbon is 200-1650 m above sea level, and although it may prefer lowland habitats, it is now largely found above 700 m due to loss of habitat.
Food and Feeding. There is some preliminary evidence that the Northern Whitecheeked Crested Gibbon is less frugivorous than is typical of most gibbons. Leaves (36%) and shoots (17%) comprise the largest proportion of the diet, with significant amounts of fruit (39%) and small amounts of flowers (4-4%) and insects (3-6%). Fruit is consumed at higher frequencies during periods of high availability in the rainy season; they eat more leaves and travel greater distances in the dry season.
Breeding. Limited data are available on reproductive parameters in both wild and captive white-cheeked gibbons. The gestation period is 200-212 days. There is no conclusive evidence for birth seasonality. Infants have a whitish-buff natal coat that changes to the dark color phase at 6-18 months, which males retain into adulthood. With sexual maturity, females change again, from their blackjuvenile coat to the characteristic yellow or buffy coat of adults, with a complete color-phase change occurring between six years and eight years and eight months in one female. Sexual maturity occurs at 6-8 years of age, but captive white-cheeked gibbons have bred as early as four years old. Average life span in the wild is unknown, but captive individuals have lived for up to 45 years.
Activity patterns. The Northern White-cheeked Crested Gibbon is diurnal and arboreal. Activity begins just before dawn, often with loud calls.
Movements, Home range and Social organization. Very little is known about the behavioral ecology of white-cheeked gibbons. Most information comes from the very small Chinese population and details about the Laotian and Vietnamese populations are based on anecdotal field observations. Nevertheless, life history characteristics of this species seem to be similar to those of other gibbons. It is territorial, living in monogamous family groups of an adult pair and their immature offspring. Average group size in Yunnan Province, China, was 3-8 individuals (range 3-5, n = 9), and anecdotal reports from Vietnam suggest group sizes of 3-5 individuals.
Status and Conservation. CITES Appendix I. Classified as Critically Endangered on The IUCN Red List. The Northern White-cheeked Gibbon is legally protected in China, Vietnam, and Laos. It occurs in 16 protected areas: Shangyong and Mengla nature reserves in Yunnan, China; Muong Nhe, Pu Hu, Xuan Lien, Pu Hoat, Pu Huong, and Ke Go nature reserves and Pu Mat and Vu Quang national parks in Vietnam; and Nam Et, Phou Louey, Nam Xam, Nam Kading, Phou Dene Din, Phou Phanang and Phou Khao Khoay biodiversity conservation areas in Laos. Population estimates, even from individual sites, are largely lacking. In Laos, there have been no population surveys, but due to the country’s large areas of remaining habitat inside protected areas,it is assumed to hold the majority of Northern White-cheeked Gibbons. Key population centers are likely Nam Et, Phou Louey, Nam Xam, and Nam Kading protected areas north of the Kading River. The population in Vietnam is better documented, with an estimate of less than 300 groups. Pu Mat National Park likely holds the largest Vietnamese population, with an estimated 130 groups. Other key sites may include Muong Nhe Nature Reserve and Vu Quang National Park, with few othersites in Vietnam holding viable populations and extinctions in a number of protected areas. It is likely that local extinctions will continue to occur in the near future. In China, the population of Northern White-cheeked Gibbons has declined drastically over past decades, due largely to hunting and habitat loss, and it is now restricted to two reserves, Mengla and Shangyong in Xishuangbanna Prefecture, with some reports also coming from Ly Chun County. The population may now be as small as ten individuals in three groups, with little prospect for long-term survival. Hunting for food, traditional Asian medicine, and the pet trade, combined with habitat loss, degradation and fragmentation across its range have resulted in the current dire conservation status of this gibbon. Where it occurs, populations are often small and highly fragmented, rather than evenly distributed in suitable habitats. Areas of intact forest often lack significant numbers because of hunting. Large-scale habitat conversion, along with firewood collection, human settlement, agricultural production, and timber extraction, driven by increasing human populations, remain significant threats. Conservation actions for the Northern White-cheeked Gibbon are largely lacking. In general, protected areas where it occurs are not effectively management, and only two population strongholds in the Nam Et, Phou Louey, and Nam Kading areas of Laos receive sufficient attention. Populations in Vietnam remain effectively unprotected and will continue to decline at significant rates, with local extirpations expected without conservation interventions. The long-term outlook for the few remaining individuals in China remains bleak. Effective site-based conservation that controls hunting and habitat loss and fragmentation is necessary for the survival of the Northern White-cheeked Gibbon in China. Population monitoring should be initiated in major population strongholds where site-based conservation is being effectively implemented. It is most important that the wildlife trade be controlled if it is to survive.
Bibliography. Brandon-Jones et al. (2004), Carbone etal. (2009), Chivers (2001), Dao Van Tien (1983), Deputte & Leclerc-Cassan (1981), Duckworth (2008), Fan Pengfei & Huo Sheng (2009), Fooden (1987), Geissmann (1991a), Geissmann et al. (2000), Groves (2001), Hu Yu et al. (1989), Luu Tuong Bach & Rawson (2011), Lao PDR, MAF (2011), Ma Shilai et al. (1988), Mootnick & Fan Pengfei (2011), Nguyen Manh Ha et al. (2010), Ni Qingyong & Jiang Xuelong (2009), Rawson et al. (2011), Smith & Xie Yan (2008), Van Ngoc Thinh, Mootnick, Geissmann et al. (2010), Van Ngoc Thinh, Mootnick, Vu Ngoc Thanh et al. (2010).
description: Published as part of Russell A. Mittermeier, Anthony B. Rylands & Don E. Wilson, 2013, Hylobatidae, pp. 778-791 in Handbook of the Mammals of the World – Volume 3 Primates, Barcelona :Lynx Edicions on page 789, DOI: 10.5281/zenodo.6727957