Nomascus nasutus 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Primates Hylobatidae

Scientific Name: Nomascus nasutus (Kunkel d'Herculais, 1884)
Common Name(s):
English Cao-vit Gibbon, Eastern Black Crested Gibbon
Taxonomic Notes: Nomascus nasutus has been variously considered either as a species in its own right (sometimes as conspecific with N. hainanus), or as a subspecies of N. concolor; it is here recognized as a species distinct from N. hainanus and N. concolor, based on differences in vocalizations and fur colouration (T. Geissmann pers. comm. 2006).

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2acd; C2a(i); D ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Bleisch, B. & Geissmann, T.
Reviewer(s): Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)
Listed as Critically Endangered because of an observed decline of at least 80% over the past 45 years (three generations) due primarily to hunting and habitat loss; and because its population size is less than 250 mature individuals, with no subpopulation greater than 50 mature individuals, and it is experiencing a continuing decline; and because its population size is less than 50 mature individuals.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is found in a small area of northeastern Viet Nam and southeastern China, northeast of the Red River, where it is restricted to the Phong Nam-Ngoc Khe Mountains, Trung Khanh District, northern Cao Bang province, and adjacent forest in Jingxi County, Guangxi (Geissmann et al. 2002, 2003b; W. Bleisch pers. comm.). It is possibly still extant in neighbouring Hoa Binh province, Viet Nam, as well, and in 2002 it was additionally reported from Kim Hy forest in Bac Kan province (which has since been proposed as a nature reserve). The range seems to have formerly extended from Ha Long Bay south to the Red River delta; gibbons of some species formerly lived in adjacent areas of southeastern China (Guangdong and Guangxi provinces), but are thought to have almost completely disappeared from there during the 1950s (Geissman et al. 2000; Fellowes et al. 2003). It is possible that some individuals still remain in isolated pockets of inaccessible karst forest.
Countries occurrence:
China; Viet Nam
Additional data:
Lower elevation limit (metres):50
Upper elevation limit (metres):900
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species was thought to be possibly extinct (Geissmann et al. 2000, 2003a), but a surviving population was found in 2002 (Geissmann et al. 2002, 2003b; La Quang Trung et al. 2002; La Quang Trung and Trinh Dinh Hoang 2004). The latter has since been extensively surveyed, revealing as of August 2002 some 26-28 individuals living in five separate groups in the Phong Nam-Ngoc Khe forests (Geissmann et al. 2002, 2003; La Quang Trung and Trinh Dinh Hoang 2004). In 2005, a survey team estimated a population of 35-37 individuals (Vu Ngoc Thanh et al. 2006). An even more recent survey found at least two groups with an estimated 10 individuals total in China on the other side of the border from the known Viet Nam population (Tan Weifu pers. comm. 2006). There have been additional surveys in other forest patches in the surrounding area, but no other extent populations have been found (Geissmann et al. 2000, 2003a; Geissmann and Vu Ngoc Thanh 2001; La Quang Trunget al. 2002; Fellowes et al. 2003).
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:45-47
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:This species historically inhabited lower montane and limestone forests, in a wet tropical monsoon climate, at an altitude range of 50-900 m (Dao Van Tien 1983). The known population is now entirely restricted to limestone forests on inaccessible karst outcrops ranging 640-800 m in elevation (Geissmann et al. 2002). Preliminary behavioral observations revealed that most of the feeding time was spent eating fruit (86.6%), whereas other food categories appeared to play a minor role: leaves (4.7%), animal matter (0.5%), undetermined food class (8.2%) (Geissmann et al. 2002).

Threats [top]

Major Threat(s): The main threat to this species, given its restricted range, is habitat loss and disturbance. What little remains of the habitat is in danger of being cleared for cultivation, livestock grazing, and firewood collection by local Viet Namese and Chinese minority people, as well as by the charcoal-making of local Chinese people (T. Geissmann and W. Bleisch pers. comm. 2006). There is also a continued threat from hunting, and the species is endangered as well from problems intrinsic to small population size and single populations, such as inbreeding effects, poor mate-choice, and risks from man-made or natural disaster (Geissmann et al. 2002, 2003b; La Quang Trung and Trinh Dinh Hoang 2004).

Conservation Actions [top]

Conservation Actions: This species is listed on CITES Appendix I, and in annex IB of the Decree No. 32/2006 ND-CP in Viet Nam. In China, all gibbons are protected as National First-Class Protected Animals. For the conservation of N. nasutus in Viet Nam, the Cao Bang Forest Protection Department established a Species and Habitat Conservation Area, with a joint forest protection system that involves communities, a ranger force, and border patrol. Fauna and Flora International is also partnering with the Cao Bang Rural Development Project to encourage sustainability and conservation education and research in the local communities (La Quang Trung and Trinh Dinh Hoang 2004). Also, there are rural energy projects underway to reduce the use of charcoal, as well as community patrols. In China, a proposition has been made recently for the establishment of strict conservation areas for all remaining forests near known gibbon groups.

Citation: Bleisch, B. & Geissmann, T. 2008. Nomascus nasutus. The IUCN Red List of Threatened Species 2008: e.T41642A10526189. . Downloaded on 23 September 2018.
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