Threatened primates in southern Vietnam€¦ · primates. Following faunal surveys of existing and proposed protected areas in Vietnam between 1988 and 1991, this paper documents

Threatened primates in southern Vietnam

Jonathan C. Eames and Craig R. Robson

Vietnam's exceptionally rich fauna is threatened by habitat loss and hunting.Although a system of protected areas has recently been developed, many of the sitesselected are subject to human encroachment, hunting pressure and other forms ofexploitation. Other protected areas may be too small to hold viable populations ofprimates. Following faunal surveys of existing and proposed protected areas inVietnam between 1988 and 1991, this paper documents the status of and identifiesthreats to three species of threatened primate: white-cheeked gibbon Hylobatesleucogenys gabriellae, red-shanked douc langur Pygathrix nemaeus and black-shanked douc langur P. nigripes.

Primate diversity in Vietnam

The forests of Vietnam contain the highest pri-mate diversity in Indochina (Burma, Thailand,Laos, Cambodia, and Vietnam) in terms ofboth levels of endemism and taxonomicuniqueness (Eudey, 1987). At least 16 speciesof primate occur in Vietnam and of these thelesser slow loris Nycticebus pygmaeus, tonkinsnub-nosed monkey Rhinopithecus avunculusand three subspecies of Francois's leaf-monkey Trachypithecus francoisi are endemic(T. /. poliocephalus, T. f. delacouri and T. /. hatin-hensis). Two other species, the red-shankeddouc langur Pygathrix nemaeus and black-shanked douc langur P. nigripes, are endemicto Indochina (Eudey, 1987).

Until recently the crested gibbon Hylobatesconcolor was treated as a single species anddivided into eight subspecies, of which four,H. c. concolor, H. c. leucogenys, H. c. siki and H.c. gabriellae, are found in Vietnam (Eudey,1987). However, based on evidence of sym-patry, morphology and behaviour this speciesis now generally treated as two full species:the black-crested gibbon H. concolor and thewhite-cheeked gibbon H. leucogenys, incorpor-ating the subspecies H. 1. siki and H. I. gabriellae(Bleisch and Chen Nan, 1990).

Contemporary information on the status,distribution and threats to Vietnam's primatesis scant. Following a recent review of the con-servation status of primates in the Indochinese

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subregion (MacKinnon and MacKinnon, 1987),information on the status of Francois's leaf-monkey, Phayre's leaf-monkey Trachypithecusphayrei, black-crested gibbon and white-cheeked gibbons, H. 1. leucogenys and H. I. siki,in northern Vietnam have recently been col-lected (Ratajszczak et al., 1990). The purpose ofthis short paper is to present the latest infor-mation on the status of white-cheeked gibbonH. 1. gabriellae (and possibly H. I. siki), red-shanked douc langur and black-shanked douclangur in central and southern Vietnam andplace this information within the context ofprevailing environmental conditions.

Deforestation - the major threat

Although historically Vietnam was almostcompletely forested, the country has now lostover 80 per cent of its original cover. Todayjust 10-12 per cent of closed tropical forest re-mains of which less than 1 per cent is in a pris-tine state (FAO, 1987 and FAO/UNEP, 1981 inCollins et al., 1991). The current rate of forestloss is estimated at 3110 sq km per year(Collins etal, 1991).

During the Vietnam War (1963-1975) an es-timated 22,000 sq km of agricultural land andforests were destroyed, largely in the south ofthe country (Collins et al, 1991). Over 13million tonnes of bombs and 72 million litresof herbicides were sprayed on the forests of

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THREATENED PRIMATES IN SOUTHERN VIETNAM

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Figure 1. Map of Vietnamshowing localities mentioned inthe text.

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Hon Nga-Cong Troi-Bi Doup Massif!u -r , »Da LotHo Tuyen Lama iNui Da Dung* «Di Linh

Nam'.Bai Cat Tien National Park- X f w S i S Deo Nui San

-8°

South China Sea

Vietnam (CVRER, 1985), with 12 per cent ofthe forests in the south of the country beingsprayed at least once (Collins et ah, 1991).

During and since the Vietnam War thehuman population has grown rapidly; its cur-rent 66.8 million people make Vietnam themost densely populated country in Indochina.With a growth rate of 2.4 per cent the countryhas one of the world's most rapidly growingpopulations, which is expected to peak at 168million in 2125 (Collins et al., 1991).

Approximately 80 per cent of the popu-lation are engaged in subsistence agricultureand are totally dependent on forest lands andtheir products to meet basic needs, such asfuelwood, timber for construction and palmfronds for making the conical hats worn by

most rural Vietnamese. The remaining forestsare subject to commercial logging, hunting,and clearance for agriculture and settlement.

The economy of Vietnam was devastated bythe war and has been slow to recover for sev-eral reasons. As a result Vietnam may havebeen forced to exploit its forests for timberand rattan at a greater rate than would other-wise have been the case.

The protected areas system

The Vietnam Government inaugurated thefirst national park at Cue Phuong in 1962(Hoang Hoe and Vo Quy, 1991). Six nationalparks, 28 nature reserves, five historical and

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J. C. EAMES AND C. R. ROBSON

cultural reserves and two unclassified areashave been designated to date, with an areatotaling 10,945 sq km (Collins et al., 1991).Responsibility for developing and managingthis programme lies with the Ministry ofForests.

Many of the areas selected have been de-graded by war and commercial logging andare threatened by agricultural encroachment,wood-cutting and hunting. Furthermore, littleattention has been paid to identifying theseareas on the basis of their biodiversity or lev-els of endemism. For example, recent researchhas identified three 'biodiversity hotspots' inVietnam of which only 0-5 per cent are in pro-tected areas (ICBP, 1992).

To assist in obtaining baseline data theInternational Council for Bird Preservation(ICBP), in collaboration with the Forest BirdsWorking Group of the Centre for NaturalResources Management and EnvironmentalStudies (CRES), carried out faunal surveys inexisting and proposed protected areas inVietnam. Surveys were undertaken in CuePhuong, Bach Ma and Nam Bai Cat TienNational Parks, Kon Cha Rang Nature Reserveand Nui Tarn Dao Historic/Cultural Reserve(Figure 1). This work focused mainly onthreatened bird species but also attempted tocollect data on primates, the results of whichare presented in this paper.

Survey techniques

The presence of primates in an area wasusually first determined by conducting inter-views with local people. These were under-taken on an ad hoc basis and invariably tookthe form of group discussions with older menand hunters. Informants were asked if theyknew of any primates in the area and to de-scribe pelage or to imitate the call. Informantswere further encouraged to produce materialevidence such as skin or skulls. Informants'reports were augmented with direct obser-vation and records of calling individuals.

In Bach Ma and Nam Bai Cat Tien NationalParks the time and position of calling white-cheeked gibbons were plotted on 1:25,000

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maps and the extent and suitability of avail-able habitat were noted. Surveys were under-taken during the early morning to coincidewith the peak period of calling activity.

It was not possible to employ a quantitativemethod for surveying red-shanked and black-shanked douc langurs for a number ofreasons. Unlike white-cheeked gibbons, douclangurs do not have loud territorial calls. Theyappear to occur at low density (either nat-urally or as a result of hunting pressure) andare generally quiet when foraging. In ad-dition, the topography of survey sites wasoften steep and because of time constraints itwas not considered feasible to undertake tran-sects or point counts.

Results

During three periods of fieldwork undertakenduring 1988,1989/90 and 1991, white-cheekedgibbons, and red-shanked and black-shankeddouc langurs were recorded in several forestareas in southern Vietnam, including Bach Maand Nam Bai Cat Tien National Parks.

Bach Ma National Park

Bach Ma National Park covers approximately190 sq km. The topography is steep and pre-cipitous, with elevations ranging from sea-level to c. 1450 m. Forest types in the parkhave been classified as closed broadleavedtropical evergreen seasonal lowland, domi-nated by Dipterocarpaceae, Fabaceae,Meliaceae and Sapindaceae (CVRER, 1985)and tropical montane evergreen forest(MacKinnon and MacKinnon, 1986).

Much of the park was subject to chemicaldefoliant spraying during the Vietnam War.Subsequently it was logged until 1989 and iscurrently threatened by logging, rattan extrac-tion, hunting and gold mining (Robson et ah,1991; Eames and Robson, 1992).

Nam Bai Cat Tien National Park

Nam Bai Cat Tien National Park covers 350-365 sq km. The west of the park is occupied by

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Deforestation by hill-tribes on the Di Linh Plateau - habitat of black-shanked douc langur (Jonathan Eames).

a range of forested hills between c. 150 and300 m in elevation, while the centre and eastare level lowland. The vegetation comprises amosaic of primary evergreen forest and sec-ondary forest formations, including bamboo,resulting from logging and agricultural clear-ance. Riparian habitats, including swamp for-est, are found in the centre of the park. Theforests have been classified as lowland semi-evergreen (MacKinnon and MacKinnon, 1986)and closed broadleaved tropical evergreenseasonal lowland (mostly dominated byDipterocarpaceae, Fabaceae, Meliaceae andSapindaceae) with closed bamboo tropicallowland and sub-montane forest (CVRER,1985).

Some of the forest was sprayed with chemi-cal defoliants during the Vietnam War and thearea was logged until its declaration as anational park in 1978. There are several vil-lages within the park and rice and sugar caneare cultivated. The wetlands are subject tofishing and disturbance and there is wide-spread poaching (Eames and Robson, 1992).


Da Lett and Di Linh Plateaux

Da Lat and Di Linh Plateaux form a contigu-ous highland massif covering 2400 sq km,rising to 2289 m at the summit of Mount BiDoup. At higher elevations the natural climaxvegetation consists of tropical montane ever-green forest (MacKinnon and MacKinnon,1986). Much of the landscape has been subjectto modification, historically by hill tribes andlatterly by Vietnamese settlers. As a resultmost land under 1500 m has been deforestedand cultivated. Extensive forests of Pinus insu-laris are found in the region and evergreenforests are increasingly confined to the moreinaccessible and less agriculturally viableareas such as ridges and hill tops (Eames andRobson, 1992).

Thua-Thien and Quang Tri provinces

Level lowland forest in Thua-Thien andQuang Tri provinces has been completely de-stroyed by chemical defoliation and clearancefor agriculture. The remaining forest is con-

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fined to small patches, some as small as 50 ha,on ridges that form the eastern slope of theAnnamite chain. During the 1988 and 1991surveys reports were received from hill-tribevillages of the continued presence of white-cheeked gibbons and red-shanked douclangurs in these isolated forest patches (Eameset ah, 1989; Eames and Robson, 1992).

Kon Cha Rang Nature Reserve

Kon Cha Rang Nature Reserve is a proposedprotected area of 160-200 sq km in Gia Lai andKon Turn provinces. A short faunal surveywas conducted here during 1988 (Eames et al.,1989). White-cheeked gibbons were notrecorded during the survey but were said tooccur in the area (Cao Van Sung and variousBohnar tribal hunters, pers. comm.).

White-cheeked gibbon

During January and February 1990 duetingpairs of white-cheeked gibbons were recordedfrom eight areas in the centre and east of BachMa National Park (Robson et al, 1991), in pri-mary and secondary forest at elevations be-tween 200 and 500 m above sea-level. DuringApril 1991 three male white-cheeked gibbonswere heard calling alone along the Song TaTrach and Khe Thoung valleys in the south-west of the park. No pairs were recorded andno females were heard calling in this area dur-ing the survey period.

During 1990 and 1991 approximately 83 sqkm were surveyed in the park. To obtaincrude density estimates, the number of callingwhite-cheeked gibbons was divided by thesurvey area. This produced density estimatesfor the five survey areas of 0, 0.12, 0.12, 0.16and 0.16 calling males/groups per sq km.Assuming that all gibbons present wererecorded during the survey periods, that therewas no duplication of records and that gib-bons occur at equal density throughout thepark, this would give a population of 23-30males/groups in the park.

Although the subspecies concerned was notdetermined, gibbons collected in Bach Ma be-tween July to November 1989 by the Forest

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Inventory and Planning Institute, were re-ported to be H. I. gabriellae (Vu Van Dung,pers. comm.).

During December 1989 and January 1990,five pairs of white-cheeked gibbons wererecorded from three areas in the north andeast of Nam Bai Cat Tien National Park in pri-mary and logged forest at elevations rangingbetween c. 100 and 200 m above sea-level.During June 1991 calling was recorded fromnine areas in the park, including two of thoseidentified in 1989/90 (Eames and Robson,1992). The data obtained is insufficient to at-tempt to determine the density of white-cheeked gibbons in Nam Bai Cat Tien. Most ofthe park remains unsurveyed and there isprobably extensive habitat for gibbons in thehilly west of the park. The subspecies in-volved was determined as H. I. gabriellae onthe basis of an animal caught in the park andheld by a villager and our own observations ofa pair.

During the May and June 1991 surveyswhite-cheeked gibbons were reported by hilltribes on the Da Lat Plateau, from the HongNga-Cong Troi-Bi Doup Massif and Ho TuyenLam, and on the Di Linh Plateau, from Nui TaDung and Nui Braian. White-cheeked gibbonswere heard calling from four areas on MountBi Doup at c. 1700-2000 m. Dueting pairs wereheard in two of the four areas. During 72 man-days in the field during January 1990 and Mayand June 1991, white-cheeked gibbons wererecorded only on 2 days. Subsequently, on 3January 1992, a dueting pair was heard callingat 1500 m at Ho Tuyen Lam. Most of the sur-veys were conducted at elevations rangingfrom 1500 to 2000 m and it is clear that thespecies is scarce or absent from most of theforest in this altitudinal range. Although theecological requirements of this species are vir-tually unknown, it is probable that forest inthis altitudinal range is sub-optimal. How-ever, other factors affect the status of white-cheeked gibbon in the area. The remainingtracts of evergreen forest are subject to in-creasing fragmentation by clearance for agri-culture, notably by slash-and-burn agriculturepractised by the hill tribes, and commerciallogging. Both these activities cause not only




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deforestation but also, because of regularburning, promote the development of Pinusinsularis fire-climax habitats, thereby reducingthe extent of the evergreen forest on which thewhite-cheeked gibbon depends.

Red-shanked douc langur

During the 1990 survey in Bach Ma NationalPark red-shanked douc langurs were recordedtwice (Robson, 1990, unpubl. data). A group ofthree or four animals, including one juvenile,was observed on 27 January. The forest at thissite had been sprayed with chemical defoliantbut showed good signs of regeneration. Thecanopy was 6-10 m high and closed canopycover exceeded 50 per cent. The second recordwas of a solitary male in primary forest at 700m on 9 February. Canopy cover was again es-timated at more than 50 per cent.

Black-shanked douc langur

Although none was seen, black-shanked douclangurs were reported from the centre andwest of Nam Bai Cat Tien National Park dur-ing the 1990 and 1991 survey periods. Morerecently a group of four black-shanked douclangurs was observed in the east of the park inprimary forest at c. 150 m on 30 January 1991.

On the Di Linh Plateau the black-shankeddouc langur was recorded at two sites: on 6June 1991, 10-15 animals were observed onNui Pantar at 1350 m. The following day twotroops of c. 20 and c. 10 animals were locatedon Deo Nui San at c. 1200 m. Additionallyduring May and June 1991, we received re-ports of this species from the Hon Nga-CongTroi-Bi Doup Massif on the Da Lat Plateau atc. 1500 m and from Nui Ta Tung and NuiBraian on the Di Linh Plateau. The paucity ofrecords from the Hon Nga-Cong Troi-BiDoup Massif suggests that the species occursprimarily below 1500 m.

Hunting and trade

Both white-cheeked gibbons and black-shanked douc langurs are subject to huntingon the Da Lat and Di Linh Plateaux. On 18


Captive white-cheeked gibbon captured in Nam BaiCat Tien National Park (Jonathan Eames).

May 1991 a group of three hunters armed withan M16 semi-automatic rifle was encounterednear Klong, 17 km south of Da Lat. They werehunting white-cheeked gibbons, which theysold for traditional medicinal purposes.According to these hunters the species is usedas a tonic for pregnant women.

The skins of black-shanked douc langurswere examined at a village near Nui Ta Dungand in Di Linh (collected from Nui Braian). Inboth cases the animals had been hunted forfood. This casts doubt on the claim that localpeople seldom hunt red-shanked douclangurs because they find the meat unpalat-able or even inedible due to the high concen-trations of toxic substances absorbed with itsleafy diet (Ratajszczak, 1989).

Taxidermy is popular in Vietnam andmounted white-cheeked gibbons and black-shanked douc langurs were located regularlyin taxidermists shops and in hotel lobbies inDa Lat and along the road between Da Latand Bao Loc. As a former hill station, Da Lat isa popular tourist destination and stuffed ani-mals are popular souvenirs.

In addition to hunting for meat and med-icinal purposes, primates are further threat-ened by the wildlife trade. Primates are avail-able regularly in Cau Mong Market in Saigon.During three visits made to the market in1991, three black-shanked douc langurs andup to 13 white-cheeked gibbons were

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A male black-shanked douc langur photographedon Deo Nui San, Di Linh Plateau. This is almostcertainly the first photograph taken in the wild ofthis species (C. R. Robson).

recorded. Both species were being offered for$US 200 each (Eames and Robson, 1992). It hasbeen claimed that the red-shanked douclangur is unknown in the pet trade and sel-dom appears in the Saigon market(Ratajszczak, 1989). Because its sibling speciesclearly is traded this claim should be treatedwith caution. It is interesting to note that apileated gibbon Hylobates pileatus was beingoffered for sale $US600. This species does notoccur in Vietnam and, according to the owner,this individual was obtained in Cambodia(Eames and Robson, 1992). However, it hasbeen suggested that a small part of its rangelies within Vietnam (Ratajszczak, 1989).

Although Vietnam may soon become a sig-natory to the Convention on Trade inEndangered Species of Wild Fauna and Flora

(CITES), there is currently no legislation tocontrol the domestic trade in primates.However, the Government is preparing a newlist of protected species, which will includethree species of primates in Appendix I andeight species in Appendix II (Ratajszczak,1989).

Discussion

The density estimates for the white-cheekedgibbon population in Bach Ma National Parkare much lower than have been obtained inother studies. In a recent study of the molochH. moloch in Gunung Halimun reserve on Java,using a similar acoustic method to that used inour study, density was estimated at 2.53groups per sq km (Kool, 1992). In a study ofthe more closely related black-crested gibbonin Wuliang Mountain Reserve in China den-sity was estimated at 0.64-1.2 groups per sqkm (Bleisch and Chen Nan, 1990).

The density estimate obtained at Bach MaNational Park is lower than would be ex-pected under natural conditions and reflects acombination of factors prevalent at this site,which include logging, a history of defoliationand hunting pressure.

By simple extrapolation we can use thesefigures to obtain a crude estimate of the num-ber of white-cheeked gibbons in protectedareas in Vietnam. If it is assumed that white-cheeked gibbons are found at densities of0.12-0.16 per sq km in all the protected areas,covering a total of 3762 sq km, within thespecies's range in Vietnam, this would give anestimate of 450-600 white-cheeked gibbons.Using the 'working density' estimate of threegibbons per sq km, given in MacKinnon andMacKinnon (1987), would produce a popu-lation estimate of almost 11,300 white-cheekedgibbons in protected areas in Vietnam.Bearing in mind that gibbons will be absentfrom many protected areas because the habitatwill be unsuitable, this latter figure would ap-pear to be much too high. The actual numberof white-cheeked gibbons in Vietnam maytherefore be nearer or even below the initialestimate of 450-600.

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MacKinnon and MacKinnon (1987) esti-mated a total world population of 131,000 con-color gibbons (including H. leucogenys) with16,300 of these in protected areas. Assumingthat forest cover has remained constant at87,532 sq km (which it is unlikely to havedone), at densities of 0.12 and 0.16 gibbons persq km the world population of concolor gib-bon could be in the range 10,500-14,000 ani-mals. This is significantly less than the 131,000of MacKinnon and MacKinnon (1987) and theestimate of 228,000 for Laos and Vietnam byChivers (1977). If these estimates tell us any-thing at all, it is just how little we know aboutthe true situation and how dangerous it can beto try and estimate population sizes based onguestimates and inadequate data. However,we can assume that the white-cheeked gibbonin Vietnam is perhaps more threatened thanwas previously believed.

It is also difficult to arrive at a populationestimate for the two species of douc langur.MacKinnon and MacKinnon (1987) estimatedthat perhaps the population of both species inprotected areas was 9000 and conceded that itmay be many fewer. Our discovery of black-shanked douc langur in Nam Bai Cat TienNational Park contradicts a recent claim thatthe species at this site is the red-shanked douclangur, which was described as both commonand easily observed there (Ratajszczak, 1989).Despite the claim that red-shanked douclangur occurs in Yok Don Nature Reserve(Ratajszczak, 1989) the species was not de-tected there during a recent survey (Laurie etal, 1989). The red-shanked douc langur is be-lieved to occur in Mom Ray and Kon KhaKinh Nature Reserves (MacKinnon andMacKinnon, 1987; Ratajszczak, 1989). However,the only protected area from which the red-shanked douc langur is currently known inVietnam is Bach Ma National Park (Robson etal, 1991; Huynh Van Keo, pers. comm.). The27 January 1990 record provides firm evidencethat red-shanked douc langurs can survive insecondary forest formations following chemi-cal defoliation. Another cause for slight opti-mism was the ease with which groups ofblack-shanked douc langurs were discoveredat forest sites on the Di Linh Plateau adjacent

to a road. Despite the assertion by Ratajszczak(1989) that the black-shanked douc langur hasa lower population than the red-shanked douclangur, he presented no evidence in support ofthis claim.

Vietnam has one of the fastest growinghuman populations in the world. Most of thepopulation is rural and dependent on forestresources to meet basic needs. As forests inVietnam continue to be cleared for agricultureand for timber, primate populations will con-tinue to decline. Outside protected areas re-maining primate populations will becomemore fragmented and isolated. Many suchpopulations will not be genetically viable inthe long term and groups of animals in suchconfined areas are particularly vulnerable tohunting. This scenario is now evident in partsof Thua Thien and Quang Tri Provinces(Eames and Robson, 1992). The outlook, there-fore, for conserving forest and primate popu-lations outside protected areas appears ex-tremely bleak.

Although a protected-areas programme isnow being developed, only four of the 87 pro-posed areas currently receives any measure ofprotection. In every case the level of protec-tion is insufficient to prevent poaching orsome other form of encroachment. Althoughthis situation will, it is hoped, improve in thefuture, many of the areas so far proposed maybe too small to support viable populations ofthe primates described in this paper. To dateno protected areas have been designated thatare known to contain populations of the H. c.siki subspecies of the white-cheeked gibbon.Further survey work to identify such areas is apriority.

There is, at last, increased interest in theconservation of wildlife in Vietnam from theinternational conservation community. It is es-sential that, as the number of non-govern-mental organizations involved in practicalconservation action in Vietnam increases, theiractivities are co-ordinated and prioritized toreflect the needs of biodiversity conservation.If we are to be successful in conserving pri-mates in Vietnam, it is important that conser-vation resources are invested in the develop-ment of the protected areas programme and

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are not side-tracked into costly captive breed-ing or reintroduction programmes.

Acknowledgments

The success of our fieldwork was due to a largenumber of people in Vietnam and the UK. With re-spect to the information presented here we wouldparticularly like to thank the following: Nguyen Cu(CRES); Truong Van La (Institute for Ecology andBiological Resources, Hanoi); Le Van Chiem and thestaff of Nam Bai Cat Tien National Park; HuynhVan Keo and staff of Bach Ma National Park; DrNguyen Dang Khoi and staff of the Centre forScientific Research; Da Lat and Vu Van Dung (FIPI).We would like to express our gratitude to the fol-lowing organizations, companies and individualsfor financial support: Geo-Initiative 'ProjektTropischer Regenwald e.V.'; John Lewis Partnershippic; International Council for Bird Preservation;Vogelbescherming Nederland; Fauna and FloraPreservation Society; Royal Geographic Society;Rolex Watch Co. Ltd; World Pheasant Association;Zoological Society for the Conservation of Speciesand Populations; Conder Conservation Trust;British Ornithologists' Union; A. S. Butler CharitableTrust; Clifton Nicholson; The Bird ExplorationFund; and the Oriental Bird Club. Thanks are alsodue to Roger Cox, Simon Thirgood and RolandWirth for reading earlier drafts of this paper.

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Documents

Threatened primates in southern Vietnam€¦ · primates. Following faunal surveys of existing and proposed protected areas in Vietnam between 1988 and 1991, this paper documents