Population assessment of the northern white-cheeked crested gibbon (Nomascus leucogenys) in Pu Mat National Park, Nghe

An province

Luu Tuong Bach and Rawson, B. M.

June 2011

Citation: Luu Tuong Bach and Rawson, B. M, 2011, Population assessment of the northern

white-cheeked crested gibbon (Nomascus leucogenys) in Pu Mat National Park,

Nghe An province, Conservation International / Fauna & Flora International, Hanoi,

Vietnam

Authors: Luu Tuong Bach and Benjamin Miles Rawson, Conservation International

Date: June 2011

Funded by: Arcus Foundation and Sprague-Nowak SE Asia Biodiversity Initiative

Cover photo: Pu Mat National Park/Photo credit: Luu Tuong Bach/Conservation International All views expressed within are the author’s/authors’ alone unless attributed otherwise and do not necessarily reflect the opinion of Fauna & Flora International, Conservation International and their donor partners. While the authors and editors strive for rigor and accuracy in presenting this report, the aforementioned organizations make no representations as to completeness; suitability or validity of any information contained, and will not be liable for any errors or omissions. Reproduction of any part of this report for educational, conservation and other non-profit purposes is authorized without prior permission from the copyright holder, provided that the source is fully acknowledged. Reproduction for commercial purposes is prohibited without prior written permission from the copyright holder. COPYRIGHT © 2011 Conservation International and Fauna & Flora International

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Acknowledgements 

We would like to thank the staff of Pu Mat National Park Management Board for providing permission for

these surveys and Pu Mat staff and local community members who helped guide our team and collect data.

Thanks also to Le Van Dung for field support and Dinh Ngoc Dat for GIS analysis presented in this report.

This survey would not have been possible without the financial support of Arcus Foundation and the

Sprague-Nowak SE Asia Biodiversity Initiative

Acronyms asl Above Sea Level

ASTER Advanced Space-borne Thermal Emission and Reflection Radiometer

CI Conservation International

FFI Fauna & Flora International

GPS Global Positioning System

ha Hectares

NP National Park

NR Nature Reserve

PNR Proposed Nature Reserve

SFNC Social Forestry and Nature Conservation in Nghe An Province

ii

Table of contents Acknowledgements ......................................................................................................................................... i Acronyms ........................................................................................................................................................ i Table of contents ............................................................................................................................................ ii Summary ........................................................................................................................................................ 1 1. Introduction ................................................................................................................................................ 2 2. Methods ...................................................................................................................................................... 2 

2.1 Description of survey site ..................................................................................................................... 2 2.1.1 Location ......................................................................................................................................... 2 2.1.2 Topography and hydrology............................................................................................................ 3 2.1.3 Flora and vegetation ...................................................................................................................... 3 2.1.4 Fauna ............................................................................................................................................. 3 

2.2 Surveys ................................................................................................................................................. 4 2.2.1 Survey design ................................................................................................................................ 4 2.2.2 Data collection ............................................................................................................................... 5 2.2.3 Data analysis .................................................................................................................................. 5 

3. Results ........................................................................................................................................................ 7 3.1. Gibbon distribution ............................................................................................................................. 7 

3.1.1 Northern area ................................................................................................................................. 7 3.1.2 Central area .................................................................................................................................. 10 3.1.3 Southern area ............................................................................................................................... 10 

3.2 Density and population estimates ....................................................................................................... 10 4. Discussion ................................................................................................................................................ 13 

4.1 Population status ................................................................................................................................ 13 4.1.1 Previous surveys .......................................................................................................................... 13 4.1.2 Current population status ............................................................................................................. 13 

4.2 Threats ................................................................................................................................................ 14 4.2.1 International and national border roads ....................................................................................... 14 4.2.2 Hunting ........................................................................................................................................ 14 4.2.3 Logging ....................................................................................................................................... 15 4.2.4 Shifting cultivation ...................................................................................................................... 15 4.2.5 Gold mining ................................................................................................................................. 15 4.2.6 Non-timber forest product collection ........................................................................................... 16 

5. Conclusions and recommendations .......................................................................................................... 16 References .................................................................................................................................................... 18 Appendix 1 – Listening post locations ......................................................................................................... 21 Appendix 2 – Gibbon and other primate group locations ............................................................................. 22 Appendix 3 – Raw survey data ..................................................................................................................... 23 Appendix 4 - Photos ..................................................................................................................................... 27 

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Summary 

The northern white-cheeked crested gibbon (Nomascus leucogenys) is a Critically Endangered gibbon

endemic to Vietnam, China and Laos. The species has been determined to be almost extinct in China, and

recent surveys suggest that the population in Vietnam is likely to number less than 250 groups. Surveys by

Conservation International in Pu Mat National Park have determined that the park holds the most

significant population of the species in Vietnam, with approximately 130 groups consisting of 455

individuals. Pu Mat NP is now the highest priority for conservation of this species in Vietnam. To date, the

population’s remote location in the park, close to the Laos border, has afforded it some natural protection,

however infrastructure development in the form of roads bisecting the park through key locations for

gibbons suggests that without targeted protection, Pu Mat’s gibbon population could be in danger of

disappearing.

Loài Vượn đen má trắng (Nomascus leucogenys) là loài vượn đặc hữu của khu vực Việt Nam, Trung Quốc

và Lào hiện được xếp vào mức độ đe dọa cực kỳ nghiêm trọng về mặt bảo tồn. Loài này hiện đã được xác

định tuyệt chủng ở Trung Quốc, trong khi đó những điều tra gần đây cho thấy quần thể loài này ở Việt Nam

còn khoảng dưới 250 đàn. Những đợt điều tra được thực hiện bởi Tổ chức Bảo tồn Quốc tế (Conservation

International) ở Vườn Quốc gia Pù Mát đã khẳng định rằng khu vực này hiện là nơi trú ẩn của quần thể

vượn khả quan nhất Việt Nam ước tính khoảng 130 đàn với khoảng 455 cá thể. Vườn Quốc gia Pù Mát

hiện được coi là nơi ưu tiên hàng đầu cho công tác bảo tồn loài vượn này ở Việt Nam. Hiện nay, quần thể

loài vượn này được xác định đang tồn tại hầu hết ở khu vực giáp biên giới Việt Nam - Lào cách xa khu dân

cư và đang được bảo vệ tốt. Tuy nhiên sự phát triển cơ sở hạ tầng, đường sá bên trong Vườn Quốc gia Pù

Mát hiện đang chia cắt những sinh cảnh sống quan trọng nhất đối với các đàn vượn và nếu không có các

mục tiêu bảo vệ thì quần thể vượn đen má trắng ở đây có thể bị đe dọa nghiêm trọng trong tương lai.

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1. Introduction 

The northern white-cheeked crested gibbon (Nomascus leucogenys) is a highly threatened primate

distributed historically in Vietnam, Laos and China. The species was recently uplisted from Data Deficient

to Critically Endangered on IUCN Red List of threatened species which reflects improved knowledge about

the species highly threatened status (Bleisch et al. 2008). The species has almost been extirpated in China,

where as few as three groups may remain (Fan Pengfei & Huo Sheng 2009). In Laos, the situation is largely

unknown, however viable populations may remain in at least three locations in the north of the country,

although there are no survey data to confirm this (Duckworth 2008).

Historically, the species was widely distributed in Vietnam from the northwestern to north-central

provinces. There are museum specimens known from Lai Chau, Thanh Hoa, and Nghe An provinces (Dao

Van Tien 1983; Fooden 1996; Geissmann 1989; Geissmann et al. 2000; Ratajszczak et al. 1990). The

southern border of the species distribution in Vietnam was previously thought to be the northern bank of

the Ca river (Geissmann et al. 2000; Nguyen Manh Ha 2005), and the gibbons in Pu Mat National Park

were identified as Nomascus siki. However, recent studies on the vocalisations and genetics of the

Nomascus genus indicates that the distribution of the species now extends as far south as Vu Quang Nature

Reserve (NR) and potentially as far as Ke Go NR and Khe Nhet Proposed Nature Reserve (PNR) (Van

Ngoc Thinh et al. 2011; Van Ngoc Thinh et al. 2010a; Van Ngoc Thinh et al. 2010b; Van Ngoc Thinh et al.

2010c). As a result of this range extension, Pu Mat NP is now considered within the range of N.

leucogenys.

Based on this range extension and the highly threatened nature of N. leucogenys Conservation International

(CI) conducted surveys in Pu Mat NP as part of a program of work to determine priority locations for the

conservation of the taxon in Vietnam and to provide the most up-to-date information for a revision of

Geissmann et al. (2000), Status Review of Vietnamese Gibbons: 2011.

2. Methods 

2.1 Description of survey site 

2.1.1 Location 

Pu Mat National Park (180 46' - 190 12'N, 1040 24' - 1040 56'E), situated in the northern Annamite

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mountains, lies in Tuong Duong, Con Cuong and Anh Son districts, Nghe An province. Pu Mat National

Park was upgraded from nature reserve to national park in 2001 following Decision No. 174/TTg of the

Prime Minister. The total area of the park is 91,113 hectares (ha) including 89,517 ha of strict protection

area and 1,596 ha of forest rehabilitation area (Tordoff et al. 2004).

2.1.2 Topography and hydrology 

Pu Mat NP has an elevation range of 100 to 1,841 masl, although approximately 90% of the park is under

1000 m in elevation (Tordoff et al. 2004). The park consists of low elevation forest along the eastern border

of the park, with topography becoming increasingly mountainous as one heads west towards the

international border with Laos. The site is a watershed for four rivers, Khe Thoi, Khe Bu, Khe Choang, Khe

Khang, which directly support irrigation of crops and drinking water for the 50,000 ethnic minority

communities living in the buffer zone of the National Park and is recognized by these local communities as

the most significant value provided by park (Roberton et al. 2003). More broadly, the national park is also a

watershed for the Ca River basin.

2.1.3 Flora and vegetation 

Pu Mat National Park consists of a significant extent of lowland evergreen forest, with some lower montane

evergreen forest at higher elevations close to the Laos border (Tordoff 2002; Tordoff et al. 2004). Extent of

evergreen forest within the park is significant, with an estimated 79,480 ha remaining (our analysis – see

methods section below). The area is one of the largest remaining forest blocks in Vietnam and is of

international significance (Tordoff et al. 2004). Botanical inventories suggest at least 2,461 plant species

occur at the site, some of which may be new to science (Tordoff et al. 2004).

2.1.4 Fauna 

The importance of Pu Mat NP for primate conservation in Vietnam is well recognized, with a very high

diversity of species including nine taxa from five genera. Confirmed records for the site include, northern

white-cheeked crested gibbon (Nomascus leucogenys), stump-tailed macaque (Macaca arctoides),

Assamese macaque (M. assamensis), northern pig-tailed macaque (M. leonina), rhesus macaque (M.

mulatta), red-shanked douc (Pygathrix nemaeus), grey langur (Trachypithecus phayrei crepuscula), Bengal

slow loris (Nycticebus bengalensis) and pygmy slow loris (Nycticebus pygmaeus) (Greiser Johns 2000;

Grieser Johns et al. 2004; Nguyen Thanh Nhan 2004).

Pu Mat National Park is also residence of several rare mammals endemic to Indochina including the saola

(Pseudoryx nghetinhensis), Annamite muntjac (Muntiacus truongsonensis), and Annamite striped rabbit

(Nesolagus timminsi) and several other globally threatened mammals including Dhole (Cuon alpinus), tiger

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(Panthera tigris), Owston's civet (Hemigalus owstoni) and Asian elephant (Elephas maximus) (Greiser

Johns 2000; Tordoff et al. 2004). Pu Mat is also considered an Important Bird Area because of the presence

of several globally threatened species including crested argus (Rheinardia ocellata) and the rufous-necked

hornbill (Aceros nipalensis) (Tordoff 2002).

2.2 Surveys 

During the period of 2010 and 2011, Conservation International (CI) conducted five auditory surveys in Pu

Mat National Park to determine gibbon distribution, density and to estimate northern white-cheeked crested

gibbon (Nomascus leucogenys) population numbers for the park. We also informally assessed threats to the

gibbon population and to the parks biodiversity values in general for reporting to the local authorities to aid

management of the park.

2.2.1 Survey design 

We used an auditory survey approach as is common for gibbon population surveys (e.g. O'Brien et al.

2004; Rawson et al. 2009; Whittaker 2005). The method utilizes a point count approach (Brockelman & Ali

1987; Buckland et al. 2001) and takes advantage of the loud calls of gibbon groups to determine group

numbers. As gibbons are territorial, calls coming from similar locations across days can be assessed to

come from the same or different groups, making cumulative counts possible.

We used a random stratified survey methodology to assess gibbon density and to make population

estimates for Pu Mat National Park. A total of 18 listening posts were used in this calculation, nine of

which were positioned below 700 masl, and nine of which were positioned above 700 masl. This approach

was used to assess differences in density and population in lowland and lower montane areas which were

assumed to have suffered differential impacts from habitat degradation and hunting pressure. Survey effort

was intended to be greater (originally 30 posts were planned), and thus sample sizes are smaller than ideal

for a stratified survey, however we present density and population estimates for each strata independently

as well as collectively. An additional six opportunistic listening posts were used which were not part of the

survey design. These posts are only used to provide minimum numbers of gibbons present (i.e. those

gibbons heard) and are not included in calculations of density or population for the park.

Posts were located at least 3 km apart from each other, avoiding double counts of gibbons from multiple

posts. An online random number generator was used to select one square in which the first listening post

was placed. Additional listening posts were placed in 1km2 squares at equal distances across the park.

Listening posts were placed on high points (peaks or ridges) within selected squares. The precise location

of each listening post within each square was chosen using a topographic map.

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2.2.2 Data collection 

To prepare for field surveys, a short training course was conducted at Pu Mat National Park with an

emphasis on gibbon identification, behavior, distribution, habitat preference and gibbon survey techniques.

The participants chosen to attend the training course were eight staff of the park including five local rangers

from five ranger stations around Pu Mat National Park and three technical staff from the Management

Board. In addition to theory lessons, the participants were trained to use Global Positioning System (GPS)

units, compasses and topography maps. On one morning, training was conducted in field conditions and

gibbon vocalisation recordings were played back to help students familiarize themselves with gibbon's

vocalizations and to practice using GPS units and compasses. After the course, trainees participated in field

surveys and collected data on gibbon vocalisations.

Surveys were undertaken by two consultants to CI, two members of Pu Mat National Park Technical staff,

and four local guides for each survey. All the listening post locations were recorded using GPS units (see

Appendix 1 and Figure 1). Each team surveyed a different location, with each survey team consisting of

one to two surveyors, who were trained to collect data on gibbon vocalizations, and one local guide. Data

was collected at listening posts between 5:00 and 10:00 each morning. High positions such as mountain

peaks and ridge-tops were used as listening posts. Two days were spent at each listening post for 15

surveyed posts, with one day spent at one post, three days spent at one post and four days spent at one post.

Visual records of gibbon groups and individuals were also opportunistically made. All gibbon vocalisations

heard while accessing the site were recorded and the locations they were heard from were listed as listening

posts and numbered as LP# (see Appendix 1).

Information on gibbon vocalisation were recorded on gibbon vocalisation data sheets. Data recorded every

day regardless of detection of gibbon groups included listening post, arrival time, departure time and

weather (see Appendix 3). Data collected when vocalisations were heard included time, compass bearing to

calling group, estimated distance, and call type (duet/solo) (see Appendix 3).

2.2.3 Data analysis 

We calculated the cumulative number of groups heard over the survey period from each listening posts

based on data such as vocalisation time, bearing and distance (Brockelman & Ali 1987). While there are

issues with this approach (Van Ngoc Thinh et al. 2010c), the low density of gibbons at the site meant that

the risk of inaccurate cumulative counts was low.

We calculated, correction factors, gibbon group density and total gibbon population for Pu Mat NP using

the methods outlined in Rawson & Vu Tien Thinh (2011). See that publication for more details, however an

outline of methods is given below.

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As gibbon groups do not sing everyday (e.g. Rawson 2004) we used the method of Xuelong Jiang et al.

(2006) to determine calling frequency based on data collected at listening posts and corrected our estimates

of the number of groups at each post accordingly to include groups which are assumed present but did not

sing during the two day survey period. We estimated calling frequency on one day (p1) using the following

equation:

Where p1 = calling probability, n = average number of gibbon groups detected in one day and N = the

cumulative number of distinct gibbon groups detected in two days. We then calculated the expected calling

frequency at each post depending on number of survey days at a post using the equation:

Where P = the correction factor and k = the number of survey days at a post. We then divided the

cumulative number of groups detected at a listening post by the calling frequency to determine the number

of groups at each post (Xi).

Survey coverage for all surveys was calculated in ARCGIS 9.0, using a 1.5km buffer placed around each

listening post, resulting in each post having a survey area of 7.07 km2. The 1.5 km buffer represents the

assumed distance that gibbons can be heard from any listening post and was arbitrarily determined based

on experience. There are however issues with this kind of calculation, e.g. not all listeners are created

equal, topography can obscure or accentuate sound transmission, etc, and this represents the major

shortcoming of this approach (Van Ngoc Thinh et al. 2010c).

We calculated group density using the following equation, where D = group density, t = total number of

groups from all posts after applying the correction factor, and a = total area surveyed.

Total population for the entire site was calculated using the equation below where T = total gibbon

population and A = total area of appropriate habitat:

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Total appropriate habitat was assessed based on satellite imagery. A land cover map of Pu Mat National

Park was extracted from ASTER (Advanced Space-borne Thermal Emission and Reflection Radiometer)

imagery using an unsupervised classification method and classified into land cover classes. The map was

clipped using the Pu Mat NP boundary and extent of evergreen forest for the entire site as well as below

and above 700 masl was calculated.

We calculated the total gibbon population for the park based on an average gibbon group size of 3.5

individuals, which is conservative compared to the only estimate of groups size of 3.78 for the species from

China (Hu et al. 1989) and 4.5 individuals per group for Nomascus gabriellae in Cat Tien National Park

(Kenyon 2007). This also does not include lone individuals who are not part of a mated group.

We used Spearman Rank Correlation Coefficients to determine the relationship between altitude of

listening posts and group density using SPSS Statistics 17.0.

3. Results 

3.1. Gibbon distribution 

We surveyed a total of 24 listening posts during the survey, including 18 posts as part of the random

stratified sampling protocol and an additional six posts which were surveyed opportunistically (see Figure 1

and Appendix 1). During surveys, a total of 44 song bouts were recorded from 13 listening posts. Analysis

of these calls indicated at least 22 different gibbon groups were detected, including 19 groups recorded at

planned listening posts and three groups recorded at unplanned listening posts (see Figure 2 and Appendix

2).

3.1.1 Northern area 

In June and July, 2010, two surveys were conducted in the area of Tam Quang commune, Tuong Duong

district. During the surveys, the survey group separated into two independent groups. Five planned listening

posts and four extra posts were established for gibbon auditory surveys. Analysis indicated that ten gibbon

groups were recorded including eight groups recorded from planned listening posts and two groups

recorded from extra posts (see Figure 2 and Appendix 2).

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Figure 1 - Listening post locations in Pu Mat NP © Conservation International

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Figure 2 - Gibbon group locations in Pu Mat NP. © Conservation International

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3.1.2 Central area 

In July and November, 2010, two surveys were conducted by three survey teams in the central areas which

belong to the areas of Luc Da and Chau Khe communes, Con Cuong district. During these surveys we set

up six planned listening posts and one extra post. Analysis indicated a total of ten gibbon groups were

recorded during the survey including nine groups recorded at planned listening posts and one group

recorded at the extra listening post (see Figure 2 and Appendix 2).

3.1.3 Southern area 

Two surveys were conducted in January and March, 2011 by three independent survey teams in the

southern part of Pu Mat National Park which belongs to Mon Son commune, Con Cuong district. During

the surveys, seven listening posts were established as planned. Only two gibbon groups were recorded, both

from one listening post located in Khe Coong area in the west very close to the international border

between Vietnam and Laos (see Figure 2 and Appendix 2). Gibbons may be largely absent from this area

because of easy access from villages within the park.

3.2 Density and population estimates 

We provide estimates of group density, total population of groups and total population of individuals in Pu

Mat National Park in Table 1. We provide estimates for the area under 700 masl, above 700 masl and these

figures combined as well as for the site as a whole without stratification by altitude for comparison.

Group density for areas under 7000 masl was 0.051 (95% CI of 0.046-0.088) groups km-2, compared to

0.271 (95% CI of 0.252-0.348) groups km-2 for areas above 700 masl, suggesting significantly higher

densities in higher altitude areas. Indeed, there was a clear positive correlation between altitude of listening

posts and the number of groups detected (rs = 0.66, p = 0.003, n = 18, Spearman Rank Correlation

Coefficient), with higher altitude posts returning more records (Figure 3).

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Figure 3 - Relationship between altitude of listening posts and the number of gibbon groups detected (n = 19).

Group population estimates were based on assessments of the extent of evergreen forest, and therefore

appropriate habitat for gibbons for the park as a whole. GIS assessments suggested that 79,481 ha of

evergreen forest persists across the entire park with 40,586 ha located below 700 masl and 38,895 ha above

700 masl. Group population estimates from lowland areas was only 20 groups (95% CI of 18-34) compared

to 110 (95% CI of 102-141) groups in high altitude locations, despite having roughly equal amounts of

habitat available. Total group population estimates derived from these figures gives a total group

population for Pu Mat NP of 130 (95% CI of 120-175) groups. This is comparable to the unstratified

estimate of 128 (95% CI of 119-156) groups for the site as a whole (Table 1).

Total gibbon population, based on group estimates multiplied by 3.5 individuals per group, give a

population estimate of 70 (95% CI of 64-119) individuals below 700 masl, and 385 (95% CI of 357-494)

individuals above 700 masl, for a total site wide population of 455 (95% CI of 421-416) individuals. This is

again similar to the unstratified estimate for the site which is 449 (95% CI of 415-547) individuals.

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Strata

Group Density(km-2) Evergreen

Forest

Extent (ha)

Group Population Individual Population

Density Lower

95% CI

Upper

95% CI

Groups Lower

95% CI

Upper

95% CI

Indiv. Lower

95% CI

Upper

95% CI

Below 700 masl 0.051 0.047 0.088 40,586 20 18 34 70 64 119

Above 700 masl 0.271 0.252 0.348 38,895 110 102 141 385 357 494

Site total stratified - - - 79,481 130 120 175 455 421 613

Site total unstratified 0.161 0.149 0.197 79,481 128 119 156 449 415 547

Table 1 – Group density, group population and total population estimates for stratified and unstratified survey designs with 95% confidence intervals.

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4. Discussion 

4.1 Population status 

4.1.1 Previous surveys 

There have been various primate surveys, including those for gibbons, in Pu Mat NP in the past, however

none have attempted to estimate absolute gibbon density and population numbers. Records prior to 1999

are fragmentary and are summarized in Geissmann et al (Geissmann et al. 2000). The first genuine gibbon

surveys were conducted in 1999 and 2004 as part of the Social Forestry and Nature Conservation (SFNC)

project in the park (Grieser Johns et al. 2004). Surveys attempted to detect trends in primates across the

projects duration (Grieser Johns et al. 2004) however surveys used transect walks instead of auditory

surveys and encounter frequency was insufficient to determine relative density or trends in the gibbon

population. Georeferenced locations of gibbons detected were not reported and thus it is difficult to

determine whether records from the current survey redetected groups from this previous survey.

In 2007, Ruppell (2008), while conducting gibbon vocalization recordings in Pu Mat NP for analysis of

Nomascus systematics, reportedly surveyed 58 km2 in the southeast of the park in Khe Bong area. She

recorded only two groups from this area and estimated a density of 0.03 groups km-2. Although these

estimates come from a non-randomised survey protocol, they are similar to densities presented here for

below 700 masl where all of Ruppell’s (2008) survey effort took place. We did not redetect the two groups

Ruppell detected, although it appears our listening posts overlapped this area.

4.1.2 Current population status 

The survey reported here represents the first baseline data on gibbon density and population for Pu Mat NP.

Estimates that 130 groups and 455 individuals of Nomascus leucogenys are present in Pu Mat NP makes

this site the highest priority for the taxon in Vietnam. Most protected areas within the range of N.

leucogenys in Vietnam contain only remnant populations. Recent surveys in Pu Huong NR and Pu Hoat

PNR/Xuan Lien NR returned only 7-8 groups (Luu Tuong Bach & Rawson 2009) and approximately 12

groups (Le Huu Oanh & Rawson 2007; Luu Tuong Bach & Rawson 2010) respectively, despite being

previously thought to be strongholds for the taxon (Geissmann et al. 2000; Nguyen Manh Ha 2005). More

recently, a population in Muong Nhe NR has been found, with 16 groups detected (Nguyen Manh Ha et al.

2010). Other sites appear to hold insignificant and probably unviable populations. No population estimates

exist for Laos, although significant populations likely exist (Duckworth 2008), and the species is on the

14

edge of extinction in China (Fan Pengfei & Huo Sheng 2009).

The gibbon population in Pu Mat NP is largely restricted to higher altitude areas along the border with

Laos. Stratified estimates of population show that there are few gibbon groups expected to remain in lower

altitude areas, most likely because of the easier access to these areas which have resulted in high hunting

pressure and habitat degradation in the past. The high elevation and more peripheral areas close to the Laos

border require several days to access and this provides some natural protection. There is significant

amounts of evergreen forest on the Laos side of the border also, suggesting a larger contiguous population

exists within this landscape

There is likely opportunity for significant expansion of the gibbon population in Pu Mat NP if threats can

be controlled. Habitat quality is still good and low densities across the site are likely a result of hunting

pressure in the past, which was apparently common prior to 1995 when densities were still high (Roberton

et al. 2003). Natural densities for Nomascus leucogenys are unknown, however other taxa in the genus

regularly display higher densities (e.g. Kenyon 2007; Rawson et al. 2009; Traeholt et al. 2005; Xuelong

Jiang et al. 2006), suggesting that Pu Mat NP could support a significantly larger population of gibbons.

4.2 Threats 

4.2.1 International and national border roads 

To facilitate patrol work for border police, several roads are being made in Con Cuong and Tuong Duong

districts running from villages on the outskirts of the park and bisecting the park to the international border

between Vietnam and Laos (Figure 7). These roads will cut through locations identified as key areas for

gibbons and other wildlife in the park. This is a serious problem for wildlife conservation in the area

because the roads fragment the forest and isolate habitats and, although the roads will help local authorities

in patrol work, they will simultaneously provide people access the forest for logging, hunting and collection

of non-timber forest products. These roads are likely to exacerbate difficulties for Pu Mat National Park

management and other relevant local authorities in controlling illegal activities within the park and are

likely to lead to a further decline of gibbon populations.

4.2.2 Hunting 

Wildlife, including gibbons, are targets of hunting in Pu Mat National Park for bushmeat, traditional

medicine and pets (Roberton et al. 2003). Based on interviews and evidence of hunting activity within the

15

park, hunting is one of the biggest pressures to wildlife in the area. We recorded no direct evidence of

gibbon hunting during the surveys, but we observed many hunting camps within the park. According to the

local guides, hunters come to hunt turtles and small mammals for food and trade. During surveys in 2010

and 2011, the survey teams captured hunters several times within the park, confiscating several mammals

including stump-tailed macaque, porcupines and civets. In July 2010, the survey team of Luu Tuong Bach

found two hunters and two dried civets in one camp located near Khe Phuong area, Chau Khe commune. In

March 2011, the survey team of Le Van Dung observed and captured four hunters carrying one stump-

tailed macaque and one civet from Khe Coong area, Mon Son commune. At that time the survey team were

accessing the forest for surveys and as such the hunters and animals were released. During the survey

conducted in March 2011, we observed one rhesus macaque was kept as a pet in Bung village. According

to the owner, the animal was captured as an infant and has been kept since.

No guns were observed during the surveys, however according to local guides who participated in surveys,

hunters often hide firearms near their camps for hunting. Hunters also set up long trap lines with snare traps

along the ridges of mountain to hunt small mammals, reptiles and birds. The fences start from the base of

the mountain then runs along ridgelines, leading animals to traps along the fences.

4.2.3 Logging 

Compare to other protected areas in Nghe An province such as Pu Hoat and Pu Huong Nature Reserves,

illegal logging does not appear to be a significant pressure to wildlife and their habitats in Pu Mat National

Park. During the surveys we did not find any locations with logging. However, because of the abundance of

streams within the park that make it easy for transporting timber out of the forest, we still discovered local

people transporting timber out of the park along the streams (Figure 6). Chainsaws were occasionally heard

from listening posts during surveys in Khe Tang area. According to local rangers, most of timber logged

was not luxury timber and was for local use such as house construction.

4.2.4 Shifting cultivation 

The ethnic minorities living around Pu Mat National Park are mostly Dan Lai and Thai. Their traditional

farming practice is shifting cultivation meaning they cultivate in an area for several years before moving to

other areas. Cultivation started long before the park was established (Tordoff et al. 2004) and most local

villages have been removed out of the core zone of Pu Mat National Park, with only two villages still

inhabited in Mon Son commune. Damage from cultivation and timber extraction is still evident in the low

elevation areas near old villages with secondary forests are now in the beginning stages of succession.

4.2.5 Gold mining 

16

Illegal gold mining is fairly widespread within Pu Mat National Park often conducted by people from

outside the local community (Tordoff et al. 2004). During the survey in Khe Thoi area, Tam Quang

commune, Tuong Duong district, the survey team observed two areas being mined, with around 10 camps

in each area.

4.2.6 Non­timber forest product collection 

In the summer, many local people from the villages around Pu Mat National Park access the forest to

exploit honey. Honey hunters create fires and dense smoke to drive the bees away before taking the honey.

However, this activity has been a cause of forest fire in the park in recent years. According to the local

guides, local people can take an average of 20 – 30 liters/person/year with a price of 80,000 -

150,000VND/0.65 liters. Because of the high profit obtained from this product it is difficult for local

authorities to keep locals from exploiting this resource.

Another non-timber forest product commonly exploited in the park is young bamboo shoot collection

(Figure 5). During the survey, we observed several groups of local people accessing the forest for this

activity. In November 2010, during surveys in Khe Bu area, Chau Khe commune, the survey team found a

group of seven people collecting bamboo shoots. The collectors were expelled from the park and bamboo

shoots confiscated by the local rangers however this activity seem difficult to manage because, like honey

collection, this is an annual activity for local communities to increase their income.

5. Conclusions and recommendations 

A southerly expansion in the understood range of Nomascus leucogenys based on genetics and vocalization

analysis has brought Pu Mat NP within the distribution limits of the taxon (Van Ngoc Thinh et al. 2011;

Van Ngoc Thinh et al. 2010b; Van Ngoc Thinh et al. 2010c). This is highly significant as, based on the

findings of this and other recent surveys (Geissmann et al. 2000; Le Huu Oanh & Rawson 2007; Luu

Tuong Bach & Rawson 2009, 2010; Nguyen Manh Ha 2005; Nguyen Manh Ha et al. 2010), Pu Mat NP

holds the most significant population of the taxon in Vietnam by almost a factor of 10. It is also likely to be

a global stronghold for the taxon, although significant survey work in Laos is required to fully understand

the species global status.

Conservation action in Pu Mat NP is now one of the highest priorities for gibbon conservation within

Vietnam. Previous site-wide, high profile, well-funded efforts under the SFNC project to halt biodiversity

loss were largely unsuccessful at stopping declines in primate populations in Pu Mat NP, although rates of

decline may have slowed (Grieser Johns et al. 2004). It seems that, in the short-term, targeted gibbon

17

protection activities should be pursued as a first option for maintain the existing population. Targeted

patrols in key areas containing gibbons, in conjunction with a permanent research presence if possible, may

be the most cost-effective and efficacious approach. Other initiatives, including environmental education

and gun control measures are also required in parallel. Ultimately, however, significant financial and

technical inputs will be required for effective conservation of the gibbon population in Pu Mat NP.

Currently, the gibbon populations’ location in higher altitude areas close to the Laos border affords it some

natural protection, and is likely responsible for the taxon’s persistence in Pu Mat NP. However,

increasingly improved access due to infrastructure developments, specifically roads through key

distribution areas for gibbons (see threats section), pose a considerable threat. Increased enforcement focus

on roads leading into previously inaccessible areas is essential to avoid wildlife in these areas being

negatively impacted. Without significant and targeted protection of gibbon groups along these

developing roads, it is likely that the gibbon population within Pu Mat NP will decline quickly. This will

require coordination between park staff and border police for effective implementation.

Monitoring of the gibbon population should be conducted in conjunction with protection activities every 2-

3 years following the same methodology presented here. This should be conducted in conjunction with

wildlife trade surveys focusing on gibbons to determine whether off-take of gibbons from Pu Mat NP

continues, as population level surveys may not show definitive trends over the shorter term.

18

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Appendix 1 – Listening post locations 

LP name UTM X UTM Y m.a.s.l Location

PM02 461262 2111120 481 Khe Thoi

PM06 455314 2105115 1133 Khe Mat

PM07 460067 2106184 580 Khe Mat

PM10 454009 2099679 1011 Bu Xam Liem

PM13 456497 2093544 820 Khe Phuong

PM14 462139 2094244 619 Khe Phuong

PM16 473891 2093763 738 Khe Choang

PM17 478029 2093702 621 Khe Choang

PM19 467983 2087080 1031 Khe Ngoa

PM20 472260 2089225 979 Khe Be

PM05 449954 2104818 866 Khe Van

PM21 479238 2087532 707 Khe Be

PM22 485493 2087642 173 Ban Con

PM23 490661 2087197 594 Khe Cap

PM25 474583 2082521 786 Khe Coong

PM26 478146 2082580 563 Khe Bat

PM27 484569 2081565 323 Khe Bung

PM28 490139 2082391 406 Khe Tang

PM#2 454199 2103816 1494 Bu Xam Liem

PM#3 452289 2101172 1361 Bu Xam Liem

PM#4 453109 2101805 1277 Bu Xam Liem

PM#5 452338 2099836 ? Bu Xam Liem

PM#6 452338 2099836 ? Bu Xam Liem

PM#7 473210 2090815 ? Bu Xam Liem

Table 2 - Listening post locations. All locations in UTM WGS84.

22

Appendix 2 – Gibbon and other primate group locations 

Group # UTM X UTM Y Listening Posts

1 472696 2091428 #7

2 472534 2088473 20

3 467641 2086140 19

4 467243 2086811 19

5 462351 2094456 14

6 461757 2094767 14

7 461819 2093924 14

8 455906 2093440 13

9 456784 2092705 13

10 456263 2093905 13

11 456180 2104615 6

12 455124 2104153 #2,6

13 451523 2100529 #3

14 452741 2100752 #3,#4,#5,10

15 453667 2100619 10

16 454949 2100021 10

17 454053 2100177 10

18 454497 2100829 10

19 453024 2099853 10

20 451338 2099836 #6

21 475449 2082021 25

22 473883 2082194 25

Table 3 – Approximate locations of gibbon groups detected during this survey and posts they were heard from.

All location data in UTM WGS84.

Species UTM X UTM Y Altitude

(masl)

Locality Group size

Grey langur 456479 2093544 820 Khe Bu area ~5 indiv.

Assamese

Macaque

459853 2093556 537 Khe Bu area ~20 indiv.

Table 4 - Other primate locality records

23

Appendix 3 – Raw survey data 

UTM WGS84

Projected UTM of gibbon

group

Date Obs Sunrise Post name Wind Rain Rain n/b Time Bear D/S Dist Dist(km) Group # UTM X UTM Y

6/15/2010 Bach 5:24:00 #1 Y N N

6/14/2010 Dung 5:23:00 #2 Y Y N 6:23 60° D 2 1.0 12 455065 2104316

6/15/2010 Linh 5:23:00 #2 Y N N 5:55 80° D 2 1.0 12 455184 2103972

6/15/2010 Dung 5:24:00 #3 Y N N 5:15 230° D 2 1.0 13 451523 2100556

6/15/2010 Dung 5:24:00 #3 Y N N 5:25 162° D 1 0.5 14 452444 2100689

6/15/2010 Dung 5:24:00 #4 Y N N 8:30 184° D 2 1.0 14 453039 2100815

6/16/2010 Dung 5:23:00 6 Y N N 5:18 130° D 2 1.0 11 456083 454610

6/16/2010 Linh 7 Y N N

7/17/2010 Dung 5:32:00 6 Y Y N 7:31 120° D 2 1.0 11 456180 2104615

7/18/2010 Dung 5:33:00 6 N Y Y 8:14 125° D 2 1.0 11 456133 2104527

7/19/2010 Dung 5:33:00 #5 Y Y Y 7:25 20° D 2 1.0 14 452680 2100763

7/20/2010 Dung 5:34:00 10 Y Y Y 5:32 310° D 3 1.5 14 452860 2100702

7/20/2010 Dung 5:34:00 10 Y Y Y 5:39 5° D 1 0.5 17 454053 2100173

7/20/2010 Dung 5:34:00 10 Y Y Y 5:44 70° D 2 1.0 16 454949 2099938

7/20/2010 Dung 5:34:00 10 Y Y Y 6:13 25° D 3 1.5 18 454642.927 2100964.75

7/20/2010 Dung 5:34:00 10 Y Y Y 7:04 340° D 2 1.0 15 453667 2100653

24

7/20/2010 Dung 5:34:00 10 Y Y Y 8:34 340° D 2 1.0 15 453667 2100657

7/21/2010 Dung 5:34:00 10 Y N N 5:12 330° D 2 1.0 15 453509 2100613

7/21/2010 Dung 5:34:00 10 Y N N 5:25 20° D 2 1.0 18 454351 2100545

7/21/2010 Dung 5:34:00 10 Y N N 5:29 70° D 2 1.0 16 454949 2099835

7/21/2010 Dung 5:34:00 10 Y N N 5:37 350° D 2 1.0 15 453835 2100678

7/21/2010 Dung 5:34:00 10 Y N N 7:24 280° D 2 1.0 19 453024 2100070

7/22/2010 Dung 5:34:00 #6 Y N Y 5:39 270° D 2 1.0 20 451338 2100078

7/23/2010 Dung 5:24:00 6 N Y Y 9:25 190° D 2 1.0 12 455140 2104209

7/24/2010 Dung 5:35:00 7 N Y Y

7/25/2010 Dung 5:35:00 7 N N N

7/26/2010 Dung 5:35:00 2 N Y Y

7/27/2010 Dung 5:36:00 2 N Y Y

11/6/2010 Dung 6:02:00 17 N N N

11/7/2010 Dung 6:03:00 17 N N N

11/10/2010 Dung 6:05:00 19 Y N N 5:52 200° D 3 1.0 3 467573 2085952

11/10/2010 Dung 6:05:00 19 Y N N 6:03 260° D 2 0.8 4 467195 2086955

11/10/2010 Dung 6:05:00 19 Y N N 7:07 260° D 2 0.8 4 467195 2086969

11/11/2010 Dung 6:05:00 19 N N N 6:12 240° D 2 0.8 4 467290 2086717

11/12/2010 Dung 6:05:00 20 Y Y N 5:53 160° D 2 0.8 2 472534 2088456

11/13/2010 Dung 6:06:00 20 N N N

11/15/2010 Dung 6:06:00 16 N Y Y

11/16/2010 Dung 6:06:00 16 N Y Y

11/9/2010 Dung 6:04:00 #7 N N N 6:11 320° D 2 0.8 1 472696 2091428

25

11/6/2010 Ky 6:02:00 14 N N N 5:53 45° D 1 0.3 5 462351 2094456

11/6/2010 Ky 6:02:00 14 N N N 6:10 330° S 2 0.5 6 461889 2094681

11/6/2010 Ky 6:02:00 14 N N N 6:14 250° D 3 0.5 7 461669 2094089

11/7/2010 Ky 6:03:00 14 N N N 5:49 320° D 2 0.8 6 461625 2094883

11/7/2010 Ky 6:03:00 14 N N N 6:11 200° D 1 0.5 7 461968 2093787

11/7/2010 Bach 6:04:00 13 N N N 5:53 260° D 1 0.6 8 455906 2093492

11/7/2010 Bach 6:04:00 13 N N N 6:00 150° D 2 0.8 9 456897 2092813

11/7/2010 Bach 6:04:00 13 N N N 7:20 346° D 1 0.4 10 456400 2093941

11/7/2010 Bach 6:04:00 13 N N N 7:39 264° D 2 0.8 8 455701 2093460

11/8/2010 Bach 6:03:00 13 N N N 5:55 240° D 2 0.7 8 455891 2093293

11/8/2010 Bach 6:03:00 13 N N N 6:00 312° D 1 0.5 10 456125 2093938

11/8/2010 Bach 6:03:00 13 N N N 6:11 170° D 2 1.0 9 456671 2092544

1/19/2011 Dung 6:35:00 21 N Y Y

1/20/2011 Dung 6:35:00 21 N Y Y

1/21/2011 Dung 6:35:00 22 Y N N

1/22/2011 Dung 6:35:00 22 N Y Y

1/23/2011 Dung 6:34:00 23 N Y Y

1/24/2011 Dung 6:34:00 23 N Y Y

3/21/2011 Dung 6:05:00 25 N N N 5:55 120° D 3 1.0 21 475449 2082021

3/21/2011 Dung 6:05:00 25 N N N 6:02 230° D 2 0.8 22 473970 2082006

3/22/2011 Dung 6:04:00 25 N N N 5:48 260° D 2 0.8 22 473795 2082382

3/22/2011 Dung 6:04:00 25 N N N 7:09 260° D 2 0.8 22 473795 2082382

3/23/2011 Dung 6:03:00 26 N Y Y

26

3/24/2011 Dung 6:02:00 26 N Y Y

3/20/2011 Bach 6:05:00 27 N N N

3/21/2011 Bach 6:05:00 27 N N N

3/23/2011 Bach 6:03:00 28 N N N

3/24/2011 Bach 6:02:00 28 N Y N

27

Appendix 4 ­ Photos 

Figure 4 - Survey team in Khe Bu area

Figure 5 - Locals exploiting bamboo shoots inside Pu

Mat National Park

Figure 6 - Timber hidden under a bamboo raft being

transported out of the forest

Figure 7 - Patrol road under construction in Khe Thoi

area

Figure 8 - Assamese macaque Figure 9 - Grey langur