Southern white-cheeked gibbon (Nomascus siki)
|Weight||7 - 10 kg (2)|
Classified as Endangered (EN) on the IUCN Red List (1) and listed on Appendix I of CITES (3).
The southern white-cheeked gibbon has only recently been recognised as a distinct species; previously it was believed to be a subspecies of the northern white-cheeked gibbon (Nomascus leucogenys) (4). Species belonging to the Nomascus genus (the crested gibbons) are distinctive due to their different colour phases. Unweaned infants are buff/white and juveniles of both sexes are black. Females then change back to buff/white with a black streak on the crown or neck when they reach adulthood (2). The males remain black and can be identified by the striking white cheek whiskers that surround the corners of the mouth in a wide, bushy arc (5). Gibbons are infamous for their singing, with adult pairs performing complex duets that can be used to identify species (6).
The southern white-cheeked gibbon is found in southern Laos and central Vietnam. The northern limit of the distribution is the Nghe An Province of Vietnam, while the southern limit is unclear as there appears to be a hybridisation zone with the yellow-cheeked gibbon (Nomascus gabriellae) between the Quang Tri Province and the north of the Kon Tum Province (7).
The southern white-cheeked gibbon lives in tall primary broadleaf evergreen forest in the lowlands, which is a typically wet, tropical climate (1).
Like all gibbons, the southern white-cheeked gibbon is arboreal and spends most of its life in the canopy of the forest. It feeds on fruits and flowers and its diet is normally supplemented by young leaves and invertebrates (8). The southern white-cheeked gibbon is well adapted to this lifestyle, moving by a method known as brachiation, in which it swings between branches hanging by its elongated arms. This method of locomotion allows the gibbon to move very quickly through the forest and reach fruit that other primates are unable to (2).
Gibbons normally form groups consisting of an adult monogamous pair and two young. Each group is territorial and it is believed that the gibbons’ beautiful songs are used to enforce their territory, as well as reinforce the bond between the adult male and female (8). These songs normally occur in the early morning and last between 10 and 20 minutes (2).
The southern white-cheeked gibbon is one of the most endangered primates in Vietnam (9). It occupies an area where there is a high human population, meaning the threat of hunting, for food, the pet trade, and for use in traditional medicine, is prevalent. It is also threatened by habitat loss, as most of its natural range has been heavily fragmented through logging and agricultural encroachment (7). As a result, it is believed that the southern white-cheeked gibbon population has declined by 50 percent in the last 45 years (1).
This primate is protected from international trade as it is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), meaning that trade in this species is only permitted in highly exceptional circumstances (3). Its range covers protected areas and national parks, although there is not sufficient enforcement in these areas against forest encroachment and poaching (1). It is also protected in Vietnam at the highest level through the wildlife protection law (7).
For more information on the conservation of gibbons visit:
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The Gibbon Conservation Center:
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- Arboreal: living in trees.
- Brachiation: a method of locomotion when the animal swings hand over hand from branch to branch.
- Hybridisation: cross-breeding between two different species or subspecies.
- Invertebrates: animals with no backbone, such as insects, crustaceans, worms, molluscs, and spiders.
- Monogamous: having only one mate during a breeding season, or throughout the breeding life of a pair.
- Primary forest: primary forest is forest that has remained undisturbed for a long time and has reached a mature condition.
- Subspecies: a population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
- Territorial: describes an animal, a pair of animals or a colony that occupies and defends an area.
- Territory: an area occupied and defended by an animal, a pair of animals or a colony.
IUCN Red List (March, 2010)
Gibbon Research Lab (October, 2009)
CITES (November, 2009)
- Geissmann, T. (2007) Status reassessment of the gibbons: results of the Asian primate Red List workshop 2006. Gibbon Journal, 3: 5-15.
- Groves, C.P. (2007) Speciation and biogeography of Vietnam’s primates. Vietnamese Journal of Primatology, 1: 27-40.
- Konrad, R. and Geissmann, T. (2006) Vocal diversity and taxonomy of Nomascus in Cambodia. International Journal of Primatology, 27(3): 713-745.
- Nadler, T., Thanh, V.N. and Streicher, U. (2007) Conservation status of Vietnamese primates.Vietnamese Journal of Primatology, 1: 7-26.
- Caldecott, J. and Miles, L. (2005) World Atlas of Great Apes and their Conservation. University of California Press, Berkeley, USA
- Manh Ha, N. (2007) Survey for southern white-cheeked gibbons (Nomascus leucogenys siki) in Dak Rong Nature Reserve, Quang Tri Province, Vietnam. Vietnamese Journal of Primatology, 1: 61-66.