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.
 |
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.
Available from:
www.conservation.org/Status_of_Gibbons_Vietnam
You may also download the whole book as a PDF file (4.3 MB).
Download begins if you click here.
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Summary
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.
Threats
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.
Conclusions
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.
Site by Thomas Geissmann.
For comments & suggestions, please email to
webmaster@gibbons.de
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