Rawson, B.M., Insua-Cao, P., Nguyen Manh Ha, Van Ngoc Thinh, Hoang Minh Duc, Mahood, S., Geissmann, T., and Roos, C. (2011). The conservation status of gibbons in Vietnam. Fauna & Flora International and Conservation International, Hanoi, Vietnam, xiv+138 pp. ISBN: 9781903703304.

Gibbons in Vietnam: Cover

The Conservation Status of Gibbons in Vietnam

Benjamin R. Rawson, Paul Insua-Cao, Nguyen Manh Ha, Van Ngoc Thinh, Hoang Minh Duc, Simon Mahood, Thomas Geissmann, and Christian Roos

ISBN 9781903703304, 2011, Paperback, xiv+138 pages, 18 figures. Fauna & Flora International and Conservation International, Hanoi, Vietnam.

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    In several respects, the status of gibbons in Vietnam can be considered to be an indicator for the general status of the nation’s biodiversity and the natural environment. The geography of Vietnam lends itself to the extraordinary level of biodiversity for which it is known, and the diversity of gibbons in Vietnam is no exception. They can be found from the most northerly sub- tropical forests which experience cold winters at high altitudes to tropical monsoon lowland forests in the south.

    This conservation status review of gibbons in Vietnam, updates a similar review which was carried out in 2000 by Geissmann et al. (2000). That milestone report drew from available literature, examinations of museum specimens and additional field surveys as a first attempt to document the status of gibbons in Vietnam. One decade later, this current report attempts to assess trends in the populations of each gibbon species in Vietnam and the effectiveness of efforts so far to conserve them. This status review is part of a broader set of initiatives in this region which include action plans in both Laos and Yunnan Province, China, and is thus also able to give a regional context. We have collated records of gibbons from all sites in Vietnam known to have gibbons and where information can be assessed to be reliable. With so much more work carried out on gibbons during the past ten years, this report provides a clearer snapshot of the status of gibbons in Vietnam than was possible a decade ago.

Conservation Status by Species

    All gibbons in Vietnam belong to the genus of crested gibbons Nomascus. Current taxonomic understanding identifies seven species of Nomascus, all distributed east of the Mekong River (with the exception of a small population) in Cambodia, China, Laos and Vietnam, six of which are found in Vietnam (see Figure 1, page 7). The species in Vietnam being, from north to south:

1. Eastern black gibbon Nomascus nasutus
2. Western black gibbon Nomascus concolor
3. Northern white-cheeked gibbon Nomascus leucogenys
4. Southern white-cheeked gibbon Nomascus siki
5. Northern yellow-cheeked gibbon Nomascus annamensis
6. Southern yellow-cheeked gibbon Nomascus gabriellae

    The eastern black gibbon N. nasutus is the only gibbon species in Vietnam for which prospects appear to have improved during the past decade. The species was rediscovered in 2002 on the border with China in Trung Khanh District, Cao Bang Province and conservation efforts so far appear to be driving a gradual population recovery. This is the only location globally where this species is currently known to exist and this population of only about 110 individuals is now restricted to approximately 1,000 hectares of limestone forest. It was previously distributed in north-east Vietnam, with the Red River and its delta forming a natural boundary to the west and south. Fortunately, at this location there have been very few records of hunting with guns and no records of gibbons being hunted since the population was discovered. N. nasutus is the only gibbon species in Vietnam for which it can be said with any confidence that there has been an increase in population. Despite, this, given the small size of its population and highly restricted distribution, N. nasutus should be uplisted from Endangered to Critically Endangered in the Vietnam Red Data Book. Globally it is listed as Critically Endangered on the IUCN Red List.

    The western black gibbon N. concolor has been the most closely monitored gibbon species in Vietnam over the past decade. Within Vietnam it is distributed in the Hoang Lien mountain range between the Black and Red rivers. Globally most of the population of this species occurs further north in Yunnan Province, China and there is a small population in north-west Laos. In Vietnam, the population has undergone a population decline greater than 50% since surveys were first carried out in 2000 and 2001. At Hoang Lien-Van Ban Nature Reserve, the gibbon population has dropped to a level where it is no longer viable and it is possible that the Mu Cang Chai-Muong La population, slightly to the south, would have undergone a similar decline without a concerted effort to protect them over the past ten years. The experience of FFI working in the Hoang Lien Mountains should be a wake-up call for the critical need for monitoring when working on species- level conservation for gibbons or other species. Given the small size of its population, its restricted distribution and large scale recent population declines with on-going threats, N. concolor should be uplisted from Endangered to Critically Endangered in the Vietnam Red Data Book. Globally it is listed as Critically Endangered on the IUCN Red List.

    The northern white-cheeked gibbon N. leucogenys is distributed through a few areas of southern Yunnan Province, northern Laos and north-west to north-central Vietnam. Compared to ten years ago, this species is now considered to have a larger southerly distribution, as far as the Rao Nay River in Quang Binh Province. As a result of extensive survey work, during recent years a much clearer picture of the status of this species in Vietnam has emerged. All significant records of viable populations come from locations close or next to the Lao border and 79 groups have been confirmed reported since 2000. Throughout the country there may be at least 190 groups, of which most are at one location in Pu Mat National Park which probably maintains about 130 groups. This population is of global significance and may extend well into Laos. The population of gibbons in Vu Quang National Park and neighbouring forests remains largely unknown and could be very significant allowing us to speculate that the population of this species in Vietnam could be as high as 300 groups. Nevertheless, at all locations populations of N. leucogenys appear to be in decline, largely due to hunting, exacerbated by land conversion and forest fragmentation. It is known to have gone extinct relatively recently in several protected areas, and may be on the point of extinction in several other locations. Given the large scale recent population declines with on-going threats and few locations with viable populations, N. leucogenys qualifies for uplisting from Endangered to Critically Endangered in the Vietnam Red Data Book. Globally, there are very few individuals remaining in China, while populations in Laos are believed to be much larger, partly due to there being much larger areas of forest. Globally this species is listed as Critically Endangered on the IUCN Red List.

    The southern white-cheeked gibbon N. siki is now understood to have a much more restricted range than previously thought, centred on Quang Binh Province in central Vietnam. Globally it is only otherwise found in neighbouring provinces of Laos. There is insufficient data to quantitatively assess trends for N. siki as a species in Vietnam, but all indications are that with hunting being a principle threat there has been an on-going population decline. Fortunately there remain relatively large populations in tracts of forest in Quang Binh Province along the border with Laos, particularly in Phong Nha-Ke Bang National Park. Information gaps for N. siki make the status of this species the most uncertain of all gibbon species in Vietnam, but given hunting pressures and its restricted range, it probably qualifies for the status of Critically Endangered in the Vietnam Red Data Book. Globally this species is listed as Endangered on the IUCN Red List.

    The northern yellow-cheeked gibbon N. annamensis is a new species to the genus. It was described in 2010 following years of discussion and research about the taxonomic uncertainty of the gibbons distributed between the currently understood species boundaries for N. gabriellae and N. siki. N. annamensis is distinguished from these latter two species based upon differences in calls and genetic analysis. Morphologically it appears to be indistinguishable from N. gabriellae. Its range is understood to extend from the Thach Han River in Quang Tri Province to the Ba River in Phu Yen Province. This species is distributed through much of southern Laos east of the Mekong and north-east Cambodia. About 200 groups have been recorded throughout its range in Vietnam and there may be more in unsurveyed areas. The contiguous protected area of Dak Rong and Phong Dien Nature Reserves appears to hold the largest population with over 80 groups, but at much lower than natural densities as a result of previous hunting pressures. Song Thanh Nature Reserve and contiguous forests and the forests in and around Kon Ka Kinh National Park and Kon Cha Rang Nature Reserve may also have significant populations. All areas indicate declines in gibbon populations. Assuming that much of this decline has occurred over the past three generations and will continue due to hunting and some land conversion of habitat, N. annamensis may also qualify for the status of Critically Endangered in Vietnam. There are large populations reported from north-east Cambodia and likely in southern Laos, where the status is less well known. Globally, this species has not yet been evaluated on the IUCN Red List.

    The southern yellow-cheeked gibbon N. gabriellae, is the most southerly distributed species in Vietnam and probably makes up more than half the gibbons in the country. There are at least 300 gibbon groups in just two areas: Bu Gia Map National Park and Cat Tien National Park and their respective surrounding forests. The complex of protected areas and surrounding forests on the edge of the Da Lat plateau extending from Chu Yang Sin National Park down to Hon Ba National Park potentially has a large population, but there is still inadequate data on most of these locations. Additionally N. gabriellae is recorded in numerous state forest enterprises and there are likely to be more populations as yet unrecorded. The threat from hunting in southern Vietnam may be rising due to increasing demand for gibbons as pets or for use in folkloric medicine. Drawing from past trends in population declines inferred for N. gabriellae, it may qualify for the status of Endangered in Vietnam. There are large populations remaining in south-west Cambodia and globally this species is listed as Endangered on the IUCN Red List.


    Hunting with guns stands out as a primary threat to gibbons in Vietnam, and is surely the primary reason for recent population losses. The impact of hunting on gibbons in the recent past is undeniable and is illustrated by the presence of suppressed populations within areas of largely intact habitat, suggesting hunting is a primary threat. Being arboreal and relatively large, agile and conspicuous, with few non-human predators, makes gibbons particularly susceptible to gun hunting pressure. The low birth rate of gibbons compared to many other mammals means a population will take longer to recover from an intensive period of hunting pressure or, if there is sustained hunting pressure, a continuous population decline as births cannot replace the numbers being killed. Given this particular susceptibility, the health of a gibbon population can serve as a good indicator for a protected area of general levels of gun hunting pressure.

    Broadly speaking gibbons are hunted opportunistically for local consumption, for the pet trade or for any number of a plethora of inconsistent beliefs about their apparent health-enhancing properties. Within the wildlife trade itself, gibbons appear to figure less significantly than many other species, which is not to say wildlife trade is not an issue for gibbons and an apparent increasing demand for gibbons in southern Vietnam is an important concern. Hunting has decimated gibbon populations in the north and the apparent rise in demand for gibbons as pets and for medicinal purposes could have similarly devastating consequences for the remaining relatively healthy populations in southern Vietnam.

    Large-scale land use change would have caused dramatic past declines in gibbon populations throughout the country, particularly during the post-war period when the drive for economic development drove deforestation. Now most gibbons are reported from within the established protected area system, so in principle formal land-use has been stabilised for most forests where gibbons are found. In reality though, habitat loss clearly continues in protected areas, particularly through illegal logging, agricultural encroachment and infrastructure developments, such as hydropower dams or roads. The resulting improved access for hunters and reduced carrying capacity for local gibbon populations are major issues for gibbon conservation nationally. Habitat loss frequently also causes population fragmentation, leading to ever smaller and less viable sub- populations.

    Without any further human threats, some gibbon populations may already be so small that they are effectively doomed to local extirpation by natural causes, such as adverse weather conditions, forest fires, disease outbreaks, skewed sex ratios and inbreeding depression. At least six sites are known to have populations which are probably in the final stages of local extirpation. Natural causes could also have catastrophic effects on critical gibbon populations, where numbers are low enough to be considered precarious, most importantly for N. nasutus and N. concolor.


    While gibbons are afforded the highest level of legal protection as species in Vietnam, awareness of this fact by the general public and even government staff is very low and law enforcement is so weak as to render their legal status almost irrelevant. Conservation of gibbons, as with much biodiversity conservation in Vietnam, still requires the basics to start working. Obvious conservation needs include: raising awareness of the general public, local government and local communities; improved law enforcement both to tackle wildlife trade and hunting in forests; improved forest management; and participation of local communities in conservation. While this conservation status review does not attempt to proscribe detailed recommendations, we summarise below the main conclusions:

    Five of the six gibbon species found in Vietnam require gibbon-focussed conservation interventions at priority sites in order to maintain viable populations into the long-term. Two of those species are perilously close to extinction in Vietnam. Local stakeholders, especially local government, need to be more aware and supportive of protecting these critically endangered populations.

    Hunting and habitat loss through land conversion appear to have led to the dramatic recent declines in gibbon populations reported. Now, most known significant populations reside in protected areas, although populations within protected areas are still under significant threat from hunting and habitat loss.

    Hunting needs to be seriously addressed, especially in protected areas throughout Vietnam. Hunting with guns is causing rapid declines and extirpations locally, even when gibbons are not specifically targeted.

    Wildlife trade continues to be a serious issue for gibbons, especially in the south of Vietnam, for pets and as well as demand for primate-based folkloric medicine.

    At some locations relatively healthy gibbon populations remain, where there has been a focussed effort to protect gibbons and where they are afforded some natural protection by their remoteness from human settlements or rugged landscapes which are difficult to access.

    There is still very little monitoring data on gibbons, even though they are very suitable for biodiversity monitoring as an indicator species. Gibbon monitoring has been very important for conservation decision-making at Mu Cang Chai during the past decade.

    Most gibbons reside within protected areas, including all the most important known populations for each species. The protected area system should be central to a national strategy for gibbon conservation. Nevertheless, most protected areas are clearly failing to perform their primary functions.

    Further surveys in some areas would support an overall national strategy for gibbon conservation. Additional survey work is required in some areas assumed to be important but without population data. Nevertheless, there is now sufficient information for most of the important areas for gibbon conservation in Vietnam to have been identified and gibbon conservation interventions should be targeted at these sites.

    The status of gibbons in state forest enterprises remains poorly known. These forests have great potential for harbouring large gibbon populations in southern Vietnam, but appropriate management plans are required which could benefit both biodiversity conservation and the wood production industry.

    Finally, gibbons are wonderfully charismatic and benign creatures, which do not harm anyone’s livelihoods, but charm us with their beauty, acrobatics and music, and they are our closest relatives in Vietnam. If nothing can be done to secure the long-term future of gibbons in Vietnam, what hope is there for the rest of Vietnam’s biodiversity and the fragile environment its human population depends upon.

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