|Scientific Name:||Nomascus leucogenys (Ogilby, 1840)|
|Taxonomic Notes:||This taxon was formerly considered a subspecies of N. concolor. N. siki has been included in this species by some authorities.|
|Red List Category & Criteria:||Critically Endangered A2cd+3cd ver 3.1|
|Assessor(s):||Bleisch, B., Geissmann,T., Manh Ha, N., Rawson, B. & Timmins, R.J.|
|Reviewer(s):||Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)|
Listed as Critically Endangered as there is reason to believe the species has declined by at least 80% over the past 45 years (three generations) due primarily to hunting and habitat loss. Over the coming 45 years, this decline is likely to reach similar proportions for the same reasons.
|Previously published Red List assessments:|
|Range Description:||This species occurs in Viet Nam, Lao PDR and China. In Viet Nam, it occurs west and south of the Black River; it has been extirpated from several areas from which it was previously recorded and is now only known from a few localities in the north-west and north-central parts of this country (Geissmann et al. 2000). In Lao PDR, it occurs in the northern parts, east of the Mekong River, except for a small area in northwestern Lao PDR on the east bank of the Mekong at about 20°17'-20°25'N, where it was replaced by N. concolor (Geissmann et al. 2000). In the 1980s, a very small population still occurred in Xishuangbanna in southernmost Yunnan province, China, just across the border from Viet Nam (Hu et al. 1989, 1990), but the species might no longer survive there (W. Bleisch pers. comm. 2006). It was formerly sympatric with N. concolor in Luchin, Yunnan (China), and possibly also in the Ma River region in Viet Nam (Dao Van Tien 1983; Ma and Wang 1988; Geissmann et al. 2000). There may be an apparent overlap or interdigitation between the ranges of N. leucogenys and N. siki between about 19 and 20°N (Groves 2001).|
Native:Lao People's Democratic Republic; Viet Nam
Possibly extinct:China (Yunnan - Native)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||There have been no records of this species from China since 1990 despite survey work, and it might now be extinct in that country (W. Bleisch pers. comm. 2006). In Lao PDR, population numbers of this species are highest due to the larger areas of remaining natural habitat, though increased hunting since 1990 to support the wildlife trade threatens these animals. Relative to N. siki and N. gabriellae, densities and numbers of this species in equivalent forest blocks are significantly lower due to higher exploitation. Forest fragmentation is also much higher in the range of N. leucogenys than in the ranges of the other two gibbon species (Duckworth et al. 1999). In Viet Nam, the forest habitat for this species is particularly fragmented, and the data from two provinces (Lai Chau and Son La) suggest that gibbons here cannot be sustained on the remaining forest patches (Geissmann et al. 2000). In Pu Huong Nature Reserve, the number of groups remaining is less than 10, while in Pu Hoat Nature Reserve fewer than three groups survive (Nguyen Man Ha et al. 2005). In a status survey report, Geissmann et al. (2003) recorded 27 sites at which this species should have occurred, but it was only confirmed surviving at four, and may survive in a further three. Even protected areas that are known to have suitable remaining habitat, such as Cuc Phuong National Park, no longer hold any surviving gibbon populations (Geissmann et al. 2000).|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||This species is found in tall primary and heavily degraded evergreen and semi-evergreen forest. In northeastern Viet Nam and northern Lao PDR, the animals live in the lowland, in a subtropical climate with a short and not very cold winter without frost, at elevations of 200-600 m (Dao Van Tien 1983). In Yunnan province, China, the species was observed at altitudes of 700-1,000 m (Hu et al. 1989). In Lao PDR, gibbons are found from the Mekong plains up to at least 1,650 m in Phou Louey National Biodiversity Conservation Area (Duckworth et al. 1999).|
Gibbons are strictly arboreal and mainly frugivorous (Geissmann et al. 2000), but there is very little field data on the behavioral ecology of N. leucogenys. Dao Van Tien (1983) studied the content of the stomach of six wild-shot crested gibbons (genus Nomascus) from Viet Nam, including three N. leucogenys, and found 90-100% fruits, associated with some leaves and insects. This data cannot be directly compared to field observations, which usually measure the time spent eating various food items (Geissmann et al. 2000). Food composition in Xishuangbanna (southern Yunnan) included fruits (39%), leaves (36%), and flowers (5%) (Hu et al. 1989). During the rainy season (May-October), when many fruits are available, gibbons travel less, whereas in the dry season (November-April), the gibbons eat more leaves and travel for longer distances (Hu et al. 1989). Average group size in Yunnan province, China, was 3.78 (range 3-5, n = 9) (Hu et al. 1989). In anecdotal reports, group sizes of three gibbon groups from Thanh Hoa and Nghe An provinces (southern part of north Viet Nam) were specified as 3, 3, and 4 individuals, respectively (Nguyen Manh Ha et al. 2005).
|Major Threat(s):||Nomascus leucogenys has suffered from deforestation through agricultural encroachment into mountainous areas and fuel-wood and timber extraction from remaining forests, especially in China and Viet Nam. Hunting for food, traditional "medicines", and their cultural value is a major threat across the range, and is likely to have been the primary cause for the decline of the species in all three countries, including the presumed extinction of this species in China (Duckworth et al. 1999; Geissmann et al. 2000).|
This species is listed in CITES Appendix I. It is legally protected in Viet Nam (Appendix 1B of Decree 32, 2006), though enforcement against forest encroachment and poaching is not adequate in most cases. In China it is protected by wildlife protection law (issued in 1989) (L. Yongcheng pers. comm.). It occurs in a mixture of protected areas and national parks throughout its range. In Viet Nam it is present in Pu Huong Nature Reserve and Ben En National Park. In Lao PDR, it is present in Nam Et and Phou Loey, Nam Xam, Phou Khao Khoay, Phou Panang, Nam Kading, and Phou Dene Din National Protected Areas, and also in Santong Training and Model Forest. In China, it was previously reported in Xishuangbanna National Nature Reserve, but only in the two sections bordering Lao PDR.
Recommended conservation measures include prevention of hunting and wildlife trade; minimization of habitat disturbance; and research and field surveys throughout the range, specifically tape recordings, genetic analysis and photographic recordings to help better define the distribution area of the taxon relative to N. siki. This is among the most common species of crested gibbon (genus Nomascus) maintained in zoos (Varsik 2000; Gibbon Network 2006; Moisson and Baudier 2005).
Bleisch, W. and Chen, N. 1990. Conservation of the black crested gibbon in China. Oryx 24(3): 147-156.
Deputte, B. and Leclerc-Cassan, M. 1981. Sex determination and age estimation in the white-cheeked gibbon Hylobates concolor leucogenys: anatomical and behavioural features. International Zoo Yearbook 21: 187–193.
Duckworth, J.W., Salter, R.E. and Khounboline, K. 1999. Wildlife in Lao PDR: 1999 Status Report. IUCN, Vientiane, Laos.
Fooden, J. 1987. Type locality of Hylobates concolor leucogenys. American Journal of Primatology 12: 107-110.
Fooden, J. 1996. Zoogeography of Vietnamese primates. International Journal of Primatology 17(5): 845-899.
Fooden, J., Quan, G. and Luo, Y. 1987. Gibbon distribution in China. Acta Theriologica Sinica 7: 161-167.
Garza, J. and Woodruff, D. 1994. Crested gibbon (Hylobates [Nomascus]) identification using noninvasively obtained DNA. Zoo Biology 13: 383-387.
Geissmann, T. 1995. Captive management and conservation of gibbons in China and Vietnam, with special reference to crested gibbons (Hylobates concolor group). Primate Report 42: 29-41.
Geissmann, T. 1997. New sounds from the crested gibbons (Hylobates concolor group): First results of a systematic revision. In: D. Zissler (ed.), Verhandlungen der Deutschen Zoologischen Gesellschaft: Kurzpublikationen – Short Communications, 90. Jahresversammlung 1997 in Mainz., pp. 170. Stuttgart, Germany.
Geissmann, T., Dang, N.X., Lormée, N. and Momberg F. 2000. Vietnam primate conservation status review 2000 - Part 1: Gibbons Status report. Fauna and Flora International, Indochina Programme, Hanoi, Vietnam.
Geissmann, T., Xuan Dang, N., Lormée, N. and Momberg, F. 2003. Status review of gibbons in Vietnam. Asian Primates 8(3-4): 10-12.
Gibbon Network. 2006. The zoo gibbon population.
Groves C. 2001. Primate Taxonomy. Smithsonian Institution Press, Washington, DC, USA.
Groves, C. 2004. Taxonomy and biogeography of primates in Vietnam and neighbouring regions. In: T. Nadler, U. Streicher and Ha Thang Long (eds), Conservation of primates in Vietnam, pp. 15-22. Frankfurt Zoological Society, Vietnam Primate Conservation Programme, Endangered Primate Rescue Center, Cuc Phuong National Park, Hanoi, Vietnam.
Groves, C. and Wang, Y. 1990. The gibbons of the subgenus Nomascus (primates, Mammalia). Zoological Research 11: 147-154.
Ha, N.M., Hoang, T.M., Anh, P.T., Hung, L.M., Son, N.T., Dat, N.V. and Huy, D.Q. 2005. Status of white cheek-crested gibbon (Nomascus leucogenys) in North Central of Vietnam. The Great Ape Conservation Fund, U.S. Fish and Wildlife Service and Central for Natural Resource and Environmental Studies (CRES), Vietnam National University, and Allwetterzoo Münster, Germany, Hanoi, Vietnam.
Hoang Hoe and Vo Quy. 1991. Nature conservation in Vietnam: An overview. Tiger Paper 18(4): 1-9.
Hu, Y., Xu, H. and Yang, D. 1990. Feeding ecology of the white-cheeked gibbon (Hylobates concolor leucogenys) (Chinese text, English summary). Acta Ecologica Sinica 10: 155-159.
Hu, Y., Xu, H. L. and Yang, D. 1989. The studies on ecology in Hylobates leucogenys. Zoological Research 10: 61-67.
Le Trong Trai, Le Van Cham, Bui Dac Tuyen, Tran Hieu Minh, Tran Quang Ngoc, Nguyen Van Sang, Monastyrskii, A. L. and Eames, J. C. 1999. A feasibility study for the establishment of Xuan Lien Nature Reserve, Thanh Hoa province. BirdLife International Vietnam Programme and the Forest Inventory and Planning Institute, Hanoi, Vietnam.
Le Xuan Canh. 1997. Endangered primate species in Vietnam. Primate Conservation 17: 117-126.
Ma, S. and Wang, Y. 1986. The taxonomy and distribution of the gibbons in southern China and its adjacent region – with description of three new subspecies. Zoological Research 7(4): 394–410.
Ma, S.L. and Wang, Y.X. 1988. The recent distribution, status and conservation of primates in China. Acta Theriologica Sinica 8(4): 250-260.
Ma, S., Wang, Y. and Poirier, F. 1988. Taxonomy, distribution, and status of gibbons (Hylobates) in southern China and adjacent areas. Primates 29: 277-286.
Moisson, P. and Baudier, F. 2005. European studbook Number 1 (data 31.12.2004): Northern white-cheeked gibbon – Nomascus leucogenys, southern white-cheeked gibbon – Nomascus siki, red-cheeked gibbon – Nomascus gabriellae. Zoo Mulhouse, Mulhouse, Sud-Alsace.
Ogilby, W. 1840. On a new species of gibbon (Hylobates leucogenys). Proceedings of the Zoological Society of London 1840: 20–21.
Ratajszczak, R. 1988. Notes on the current status and conservation of primates in Vietnam. Primate Conservation 9: 134-136.
Roos, C. 2004. Molecular evolution and systematics of Vietnamese primates. In: T. Nadler, U. Streicher and Ha Thang Long (eds), Conservation of primates in Vietnam, Frankfurt Zoological Society, Vietnam Primate Conservation Programme, Endangered Primate Rescue Center, Cuc Phuong National Park, Hanoi, Hanoi, Vietnam.
Ruggeri, N. and Timmins, R. 1996. An initial summary of diurnal primate status in Laos. Asian Primates 5(3-4): 1-3.
Tien, D.V. 1983. On the north Indochinese gibbons (Hylobates concolor) (primates, Hylobatidae) in North Vietnam. Journal of Human Evolution 12(4): 367–372.
Varsik, A. 2000. North-American regional studbook for white-cheeked gibbon, Hylobates leucogenys and golden-cheeked gibbon, Hylobates gabriellae. Santa Barbara Zoological Gardens, Santa Barbara, CA, USA.
Wang, S. and Quan, G. 1986. Primate status and conservation in China. In: K. Benirschke (ed.), Primates. The road to self-sustaining populations, pp. 213-220. Springer-Verlag, New York, USA and Berlin, Germany.
Yang, D. and Xu, P. 1988. Observations on Hylobates leucogenys in Xishuangbanna. Sichuan Journal of Zoology 7(1): 36-38.
Yang, Y., Tian, K., Hao, J., Pei, S. and Yang, Y. 2004. Biodiversity and biodiversity conservation in Yunnan, China. Biodiversity and Conservation 13: 813-826.
Zhang, S. 1998. Current status and conservation strategies of primates in China. Primate Conservation 18: 81-84.
|Citation:||Bleisch, B., Geissmann,T., Manh Ha, N., Rawson, B. & Timmins, R.J. 2008. Nomascus leucogenys. The IUCN Red List of Threatened Species 2008: e.T39895A10272040.Downloaded on 16 December 2017.|
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