ta dung nature reserve
TRANSCRIPT
Population status of
the yellow-cheeked crested gibbon (Nomascus gabriellae) in Ta Dung Nature
Reserve, Dak Nong Province, Vietnam
Hoang Minh Duc, Tran Van Bang and Vu Long
December 2010
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Citation: Hoang Minh Duc, Tran Van Bang and Vu Long, 2010. Population status of the yellow-cheeked crested gibbon (Nomascus gabriellae) in Ta Dung Nature Reserve, Dak Nong Province, Vietnam, Fauna & Flora International / Conservation International, Hanoi, Vietnam
Author: Hoang Minh Duc, Tran Van Bang and Vu Long: Center for Biodiversity and Development, Institute of Tropical Biology
With the contribution:
Nguyen Hao Quang and Dinh Hoang Dung: Center for Biodiversity and Development, Institute of Tropical Biology
Nguyen Thanh Trung and Nguyen The Truong An: University of Natural Sciences
Date: December 2010
Reviewed by: Benjamin Rawson – Conservation International
Paul Insua-Cao – Fauna & Flora International
Funded by: Arcus Foundation
Cover photo: Part of survey team on the way to camping site/Photo credit: Tran Van Bang
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
© 2010 Fauna & Flora International and Conservation International
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Acknowledgements
I would like to thank Mr. Dan, the director of Ta Dung NR for giving permission to undertake the survey and allowing technical staff and forest rangers to participate in the survey. I would also like to thank all the technical staff and forest rangers who dedicated their time and supported this survey.
I am grateful to Dr Ben Rawson at Conservation International and Mr. Paul Insua-Cao at Fauna & Flora International for giving us a small grant to conduct this survey. Dr Ben Rawson also shared a lot of experience and skills to junior investigators of my team at the training workshop in April, and materials on gibbon surveys.
Finally I would like to thank all the local guides and porters who helped in the survey and provided information.
The Arcus Foundation provided financial support.
Acronyms
asl. Above sea level
GPS Globally positioning system
HH Household
NTFP Non-Timber Forest Product
NP National Park
NR Nature Reserve
SD Standard Deviation
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Table of contents Acknowledgements ....................................................................................................................... ii
Acronyms ........................................................................................................................................ ii
Table of contents ...........................................................................................................................1
1 Introduction..................................................................................................................................2
2 Goal and Objectives...................................................................................................................2
2.1 Goal .......................................................................................................................................2
2.2 Specific objectives ..............................................................................................................2
3 Methodology................................................................................................................................3
3.1 Description of survey site...................................................................................................3
3.1.1 Location .........................................................................................................................3
3.1.2 Topography and hydrology.........................................................................................3
3.1.3 Flora and vegetation....................................................................................................3
3.1.4 Fauna.............................................................................................................................4
3.1.5 General social conditions ...........................................................................................4
3.2 Methods ................................................................................................................................4
3.2.1 Training and selection of surveyed area ..................................................................4
3.2.2 Survey method .............................................................................................................5
3.2.3 Data analysis ................................................................................................................7
4 Results .........................................................................................................................................8
4.1 Calling records.....................................................................................................................8
4.2 Estimation of population size of yellow-cheeked crested gibbons ............................10
4.3 Threats to the yellow-cheeked crested gibbons and their habitat .............................10
5 Discussion .................................................................................................................................11
References....................................................................................................................................14
Annexes ........................................................................................................................................17
Annex 1 List of participants ....................................................................................................17
Annex 2 Details of listening posts at Ta Dung NR..............................................................18
Annex 3 Detailed information of gibbon calling records at Ta Dung NR.........................19
Annex 4 Some photos taken during the training and gibbon survey ...............................21
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1 Introduction
The yellow-cheeked crested gibbon (Nomascus gabriellae) is an endangered primate endemic to Indochina. However, the status of the species in its northern distributional limit in Vietnam remained unclear since the review of gibbon status in Vietnam in 2000 compiled by Geissmann et al. With the discovery of a new gibbon species in the north central Highlands, the northern buff-cheeked crested gibbon (Nomascus annamensis) (Van Ngoc Thinh et al. 2010a), the yellow-cheeked crested gibbons distributional limits have been reduced, with it now understood to occur in eastern Cambodia and southern Vietnam south of the Se San River and Ba River respectively (Van Ngoc Thinh et al. 2010b). In Vietnam the Dak Lak and Da Lat Plateaus are expected to support important populations of the species. However, except an ongoing survey in Vinh Cuu Nature Reserve (NR) conducted by Nguyen Manh Ha and two studies in Bu Gia Map National Park (NP) (Hoang Minh Duc et al. in prep) and Cat Tien NP (Kenyon, 2007, 2010) conservation status of the species in its geographical range in Vietnam is still unclear. This report provides some new information on the yellow-cheeked crested gibbon and threats to the species and its habitat in Ta Dung NR, a protected area located on the periphery of the Da Lat Plateau.
Ta Dung NR, an area of 22,100 ha with high biodiversity value, was established as a nature reserve on 6th January 2003. The nature reserve has been identified as a focal area for conservation in the Dong Nai River Basin Conservation Landscape (Pilgrim et al. 2009). The landscape includes a range of forested habitats, from montane evergreen and coniferous forests of the upper reaches of the Dong Nai River basin in the Da Lat Plateau to flat lowland evergreen forests of the Dong Nai River plain in the west. For species diversity, at least 931 vascular plants and 202 terrestrial vertebrates have been recorded in this area. The conservation of Ta Dung NR is essential for globally threatened mammals including the yellow-cheeked crested gibbon and the black-shanked douc (Pygathrix nigripes). The yellow-cheeked crested gibbon was first recorded in this area by Dang Huy Huynh et al. (1998) but population status remained unclear. Our recent interviews of reserve staff and local people to form a conservation needs assessment for the reserve showed that Ta Dung NR possibly supports an important population of the yellow-cheeked crested gibbon. This report will contribute to the forthcoming revision of the Vietnam Primate Conservation Status Review for Gibbons, and forms the basis of a management plan for the protection of the yellow-cheeked crested gibbon in Ta Dung NR.
2 Goal and Objectives
2.1 Goal
The goal of this survey was to determine the population size and density, the species distribution within the park, its preferred habitat within the park and the threats the species faces to educate management of the population while building capacity of nature reserve staff.
2.2 Specific objectives
To assess the population status of yellow-cheeked gibbon at Ta Dung NR.
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To identify current threats to the yellow-cheeked gibbon and its habitat.
To provide appropriate recommendations for species management and conservation.
To train local protected area staff in gibbon survey techniques.
3 Methodology
3.1 Description of survey site
3.1.1 Location
Ta Dung NR is situated within the Da Lat Plateau and forms part of the Dong Nai River Basin Conservation Landscape, comprising the entirety of Binh Phuoc, Dak Nong, Dong Nai, and Lam Dong Provinces in southern Vietnam. The NR was established under Decision No. 07/QĐ-UBND of the People’s Committee of Dak Lak Province (now Dak Nong Province) on 6th January 2003.
Its coordinates are between 11°48’ - 11°59’N and 107°54’ - 108°07’E. The total area of the reserve is 18,893 ha comprised of a strictly protected area of 9,942 ha, an ecological rehabilitation area of 4,882 ha and an administration and service area of about 4,069 ha. Ta Dung NR is located in the two communes of Dak Som and Dak Lao (Dak G’Long District), and borders six additional communes of Dak G’Long District (Dak Nong Province) and Di Linh, Lam Ha and Dam Rong Districts (Lam Dong Province). The south-western boundary of Ta Dung NR is formed by the Dong Nai River. A buffer zone area under management board control comprises about 3,241 ha, and includes some protection forest as well as agricultural land (Ta Dung, 2009a).
3.1.2 Topography and hydrology
Ta Dung NR has a rugged terrain. Elevation ranges between 750 and 1,892 m above sea level. Mountainous areas are dominated by steep slopes of 60%. Ta Dung has about 60 streams, 20 of which are perennial. These streams feed the Dong Nai River in the south of the area and Srepok River in the north of the area. There is a small lake in the strictly protected area to the west of Mount Ta Dung. The rainy season lasts from May to November and annual rainfall is about 2,413 mm (Ta Dung, 2009a).
3.1.3 Flora and vegetation
The Landscape includes a range of forested habitats, from the montane evergreen and coniferous forests of the upper reaches of the Dong Nai River basin in the Da Lat Plateau to the flat lowland evergreen forests of the Dong Nai River plain in the west.
Ta Dung NR has 6,000-8,100 ha of upland evergreen and semi-evergreen forest above c.1,000 m asl. Large areas of upland evergreen and semi-evergreen forest are not particularly common, but they also typically face less severe threats than lowland forests due to their relative inaccessibility and often limited agricultural applications. Semi-evergreen forest in the lowlands is dominated by Lagerstroemia up to c.1,000 m. The Ta Dung NR forest exhibits varying degrees of disturbance. The lower elevations at the site support an anthropogenic landscape, dominated by agricultural land and grassland.
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Previous studies documented 931 vascular plants of which several species listed in the 1992 and 2007 Red Data Book of Vietnam including Cinnamomum balansae, Pterocarpus macrocarpus, Pinus dalatensis, Rhodoleia championii and Aquilaria crassna
3.1.4 Fauna
Information on the fauna of Ta Dung NR is very limited. Dang Huy Huynh et al (2000) reported 47 species of mammal including some globally threatened species including the serow (Capricornis milneedwardsii), giant muntjac (Megamuntiacus vuquangensis), gaur (Bos gaurus), hog deer (Axis porcinus) and two endangered primates, the black-shanked douc (Pygathrix nigripes) and yellow-cheeked crested gibbon (Nomascus gabriellae) (both were present as recently as 1998). However, most of these records were based on interviews and the status of these species is unclear. Dang Huy Huynh et al. (1998) recorded 122 species of birds, 17 species of reptiles and 16 amphibian species.
3.1.5 General social conditions
The total human population in the buffer zone of Ta Dung NR in 2008 was 16,918 people in 3,667 households (HHs). While most people are indigenous ethnic minorities many Tay and Hmong ethnicities migrated from the north to the area after 2000. About 961 poor HHs (4,862 persons) are almost totally dependent on the reserve’s resources for 3-4 months of the year, while 2,599 middle wealth HHs (11,696 persons) are partially dependent on the reserve’s resources in the period between two crops (Mar– Apr) and the mid portion of the rainy season (Aug-Oct.) (Ta Dung NR, 2009b). Non-timber forest products (NTFPs) and firewood collection and hunting/trapping small animals are the main income sources of local people during periods of food shortage (Ta Dung NR, 2009b).
3.2 Methods
3.2.1 Training and selection of surveyed area
A short training course was offered to the staff of Ta Dung NR before the survey. Ten staff including four technical staff and six forest rangers from forest stations #3 and #4 attended the training. They were provided basic information about gibbons including systematics, ecological and behavioural characteristics, how to distinguish vocalizations of males and females and to distinguish duet and solo songs. Training on methods for field surveys and how to use equipment were offered over two days. In the next two days, they practiced these skills in the forest near forest station #3 to become familiar with survey methods and equipment including GPS units, compasses, range finders and binoculars. At the end of the training, we discussed our plans and selected areas to set up listening posts for the field survey.
To select suitable areas for the gibbon survey we consulted with technical staff and forest rangers during the training and also used maps of the nature reserve showing forest status. However, during our survey, we could not access three posts and had to choose alternative ones that were located in lower elevation and close to the boundary between the nature reserve and Lam Dong Province. We also omitted five posts due to poor habitat (four posts in the northern part) and inaccessibility (one post). The total listening post was 19 (Figure 2).
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Figure 1 Technical staff and forest rangers of Ta Dung NR at the training course
3.2.2 Survey method
Two survey approaches were used during this survey. Firstly, we used fixed point counts from listening posts. This method relies on the loud sound of the gibbon’s calls (Brockelman and Ali, 1987; Brockelman and Srikosamatara, 1993). Two surveyors were assigned to stay at a fixed point for two consecutive days. During our survey, it was rainy some mornings and gibbons did not call. For those days, an extra day was added to avoid bias in calling frequency caused by poor weather (Rawson et al, 2009; Rawson, 2004, 2010).
A total of six camp sites were used during the survey. A total of 19 listening posts were surveyed (figure 2), covering an area of 98.79 km2 (9,879 ha). Of that 76.79 km2 (7,679 ha) is within the boundary of Ta Dung NR and covered by suitable habitat.. Survey area was determined by using a 1.5km listening radius around listening posts, meaning each post covered an area of 7.07 km2, with areas of unsuitable habitat and overlap between posts removed.
Of 19 posts used, 14 posts were surveyed for 2 days, 4 posts were surveyed for 3 days, and 1 post was survey for 1 day. Surveys were conducted in the morning from 5:00-8:30 am. For every call, the surveyors recorded starting and ending time of all song bouts, compass bearing, and estimated distance to the group and whether the call was from a lone male/female or a duet.
Secondly, we used the used-trail transect method. Because of logistical constraints, available trails were used to determine the relative density and the average group size of the gibbon. Surveyors from the camp followed the trails to listening posts in the afternoon and from the listening post back to the camp in the morning after finishing conducting vocal surveys. When a group of gibbon was found surveyors recorded location, number of individual, distance from the observer, compass bearing, the elevation and habitat.
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Figure 2 Location of listening posts in Ta Dung NR
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3.2.3 Data analysis
Locations of gibbon groups were determined using recorded compass bearing, estimated distance from listening post to the animal/group and coordinates of the listening post. We used MapInfo 7.5 to illustrate the location of the individuals/groups on a forest status map and topography map of Ta Dung NR.
Individual groups were differentiated by their locations. Typically a rule of thumb is that records are considered separate groups if they are detected >500m apart (Brockelman and Ali, 1987), although if groups are recorded as singing at less than 500 m apart and at the same times, these might also be separated as two groups (Jiang et al. 2006). This assumption is however based on the average home range of under 20ha of gibbon, however crested gibbons’ home range appear to be considerably larger and so a larger distance between vocal events may be required to differentiate groups (Rawson 2010). Kenyon (2010) reported that average home range of yellow-cheeked crested gibbon was 41.70ha and ranged between 16.72ha and 60.50ha depending on habitats. For the average home range of 41.70 ha, the diameter of a circular territory would be 730m. We applied this figure to identify number of gibbon groups recorded during our survey. Gibbon group density was then estimated using a similar approach to that used by Brockelman and Srikosamatara (1993) and Rawson et al. (2009). The correction factor was estimated using Jiang et al. (2006). Number of groups in Ta Dung NR was then extrapolated based on density and suitable habitat size.
There are several reports on maximum hearing distance. Kenyon (2007) stated that the maximum hearing distance was about 1.5km in hilly areas and about 1.0 km in flat areas in Cat Tien NP. Other studies suggested that in good conditions one can hear gibbon vocalization 1.5km in all directions (Duckworth et al. 1995, Traeholt et al. 2005). Rawson et al. (2009) applied 1.5km and 2.0km for their study in Cambodia. In this study we did not set listening posts in a triangular formation to estimate the maximum hearing distance in Ta Dung NR. However, our results from Bu Gia Map NP showed that, depending on location, maximum hearing distance can be 1.8 km but in general it was less than 1.5km. We applied the maximum hearing distance of 1.5km to estimate the density of gibbons in the area.
Gibbon calling frequency (p) across Ta Dung NR was calculated by summing the vocalisations from all posts for a single day, on average, divided by the sum of the cumulative vocalisations of all posts over the two day period (Jiang et al. 2006). The cumulative proportion of the total number of gibbon groups heard calling over 2 survey days at listening posts (calling probability p(m)) can subsequently be determined by the equation: p(m) = 1− [1− p]m
where p = calling frequency and m = number of survey days i.e. 2
The total estimated number of gibbon groups at each listening post (Xi) was then estimated using the equation:
Xi = ni / P(m)
Where ni = cumulative number of gibbon groups heard in the two day period at listening post i, P(m) = calling probability over 2 survey days.
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The density of gibbon groups at each listening post (Di) was then calculated using the equation:
Di = Xi / ai
Where Xi = estimated number of gibbon groups at listening post i; ai = survey area at listening post i (i.e. 7.065 km2 based on a listening radius of 1.5 km) excluding unsuitable habitat and the area outside the protected area; see below. 4 Results
4.1 Calling records
From the 19 listening posts, we recorded 8 discrete groups from 7 posts (Figure 3), which included 6 groups and two lone males. This figure was identified based on 14 calling records including one female who vocalized two times in one day (one in the morning and one in the afternoon) and one call which was heard from 2 posts. The number of gibbon groups heard per listening post ranged from 0 to 2 groups (cumulative over 2 days), with a mean of 0.63 groups (± 0.08 SD). Most locations where gibbons were detected are on Mount Ta Dung at elevations between 1,300 and 1,600 m asl. In the northern part of the reserve which is dominated by mixed bamboo and broadleaf forest, only one call, a duet, was recorded.
Most calls were heard between 5:30 am and 6:30 am. The earliest call was at 5:18 am while the sun rise on that day was 5:31 and sunrise recorded during the entire survey period was 5:31~5:35 am. The average length of calls was 14 min and 16 sec. This average figure excludes three individuals that vocalized several times for durations lasting more than an hour.
Based on compass bearing, estimated distance from listening post to the animal/group and coordinates of the listening posts, we only confirmed eight individuals/groups in the area including six groups with male and female, as determined by duets, and two lone males.
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Figure 3: Calling records of gibbons at 19 listening posts in Ta Dung NR (good gibbon habitats shown in green)
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4.2 Estimation of population size of yellow-cheeked crested gibbons
Gibbon calling frequency (p) on a single day is less than 1.0 for a gibbon group. Therefore, the actual number of gibbon groups can be higher than number of groups heard during the survey. Using the method proposed by Jiang et al. (2006) we calculated gibbon calling frequency (p1) across our listening posts as 0.50. The cumulative proportion of the total number of gibbon groups heard calling over 2 survey days at 19 listening posts was calculated as 0.75
In general only duet vocalizations are used for estimation of group density. In this survey, two lone male vocalizations were recorded. Total population estimated for Ta Dung NR is based on duets (i.e. groups) only. The total estimated number of gibbon groups at 19 listening posts (Xi) was estimated using the equation:
Xi = ni / P(m) = 9.09 (95% CI 6.00 – 13.84)
The density of gibbon groups in the survey area (Di) was then calculated using the equation:
Di = Xi / ai
Di = 9.09/76.79 = 0.1183 (groups/km2) (95% CI: 0.0627 – 0.1802).
The western part of the reserve is covered by bamboo forest with some thin patches of riparian forest along streams and no longer support gibbons since its inundation by the Dong Nai #3 reservoir. Suitable forest of Ta Dung NR for the yellow-cheeked crested gibbon is approximately 100.9km2; therefore, the estimated number of gibbon groups in Ta Dung is:
Estimated groups in entire NR (100.93 km2): 11.94 (95% CI 7.89 – 18.19)
Because of the limited number of calling records no further analysis was made to assess correlations (if any) between calling probability and environmental factors.
4.3 Threats to the yellow-cheeked crested gibbons and their habitat
Hunting signs were recorded at all 19 listening posts, illegal logging was recorded at eight posts and NTFP collecting was recorded at one post (Annex 2). During our survey, we saw poachers with hand-made guns wandering in the forest several times and one time we saw them catch two bamboo rats. Available trails were rarely seen in the forest but hunting camps were erected in many places.
Based on interviews, the six main threats to gibbons and their habitat are hunting, agricultural encroachment, forest fire, infrastructure development, illegal logging and collection of NTFPs and firewood. The Dong Nai #3 reservoir and national road #28 from Dak Nong to Lam Dong, constructed to replace the old road which was inundated by the reservoir destroyed about 15% of the forested area of the reserve (Ta Dung NR, 2009b).
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5 Discussion We only recorded gibbon vocalizations from 7 of 19 listening posts. There were two reasons that may explain the low number of calling records in Ta Dung NR. The first reason is the high hunting pressure in the area. This assumption is supported by signs of hunting in the area, encounters with poachers in the forest and solo calls recorded, possibly suggesting hunting has removed mated individuals although expected ratios of lone males to groups is unknown in the species. Some areas on Mount Ta Dung that support good habitat for gibbons returned no vocalizations even after three consecutive days of survey effort (including one day of rain). The second reason could be rain. Even though we chose to conduct our survey in October to avoid heavy rain it was rainy most days during our fieldwork because of unusual weather this year (Annex 3). Rawson (2004) reported that in Cambodia, Nomascus gabriellae vocalizes more frequently in the dry season (November – April) than the wet (May – October), as rainfall appears to suppress vocal activity as did Kenyon (2007) in Cat Tien NP. Likewise, our survey in Bu Gia Map NP showed that calling probability of yellow-cheeked crested gibbon in the rainy season was 25% less than that in the dry season (Hoang Minh Duc et al. in prep).
The density of yellow-cheeked crested gibbon in Ta Dung NR was lower than for most other gibbon species and with the same species in other areas (Table 1). In Cat Tien NP, an area about 100km to the south-west of Ta Dung, Kenyon (2007) reported an average density of between 0.52 (±0.47) km-2 and 0.72 (±0.08) km-2 depending on the listening radius used for density calculations which varied between 1-1.5 km depending on the topography. Another survey should be conducted in Ta Dung NR in the dry season in order to validate the density and group estimates presented here.
Table 1: comparison of gibbon densities from other studies using the same method
Species Location Density/km2 Reference
Symphalangus syndactylus
Sumatra (Indonesia) 2.23 O’Brien et al. 2004
Hylobates agilis Sumatra (Indonesia) 0.67 O’Brien et al. 2004
Hylobates muelleri Kalimantan (Indonesia) 2.10-2.90 Nijman & Menken, 2005
Hylobates albibarbis Kalimantan (Indonesia) 2.59 Cheney et al. 2008
Hylobates albibarbis Kalimantan (Indonesia) 1.39-3.92 Hamard et al. 2010
Nomascus concolor Yunan (China) 0.67 Jiang et al. 2006
Nomascus siki Central Vietnam 1.30 Geissmann et al. 2007
Nomascus gabriellae Seima PF (Cambodia) 0.71 Rawson et al. 2009
Nomascus gabriellae Phnom Prich WS (Cambodia)
0.15 Phan Chana & Gray, 2009
Nomascus gabriellae Cat Tien NP (Vietnam) 0.52-0.72 Kenyon, 2007
Nomascus gabriellae Ta Dung NR (Vietnam) 0.118 This study
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The results from the current survey can be compared with known populations of yellow-cheeked crested gibbon throughout its distribution of eastern Cambodia and southern Vietnam. In Cambodia, Traeholt et al. (2005) estimated about 850 groups in Snoul Wildlife Sanctuary and 330 groups in Nam Lyr Wildlife Sanctuary. The population in Virachey National Park and Pheapimex concession, estimated at 5,750 groups and 1,100 groups respectively, are now classified as Nomascus annamensis (Van Ngoc Thinh et al. 2010). Rawson et al. (2009) estimated about 646-972 groups (95% CI) in Seima Biological Conservation Area. In Phnom Prich Wildlife Sanctuary about 360 groups were estimated to persist in 2005 (Traeholt et al. 2005) while 15-273 groups were estimated in 2009 based on increased survey effort (Phan Chana and Gray, 2009, 2010). These figures show that the yellow-cheeked crested gibbon is widespread and abundant in Cambodia.
In Vietnam, this species is mostly confined to a few protected areas such as Yok Don NP, Chu Yang Sin NP (Dak Lak Province), Ta Dung NR and Quang Truc State Forest Enterprise (Dak Nong Province), Bidoup Nui Ba NP (Lam Dong Province), Phuoc Binh NP (Ninh Thuan Province), Bu Gia Map NP (Binh Phuoc Province) and Cat Tien NP and Vinh Cuu NR (Dong Nai Province). In detail, Kenyon (2007) estimated a density of between 0.52 (±0.47) group/km2 and 0.72 (±0.08) group/km2 depending on the listening radius used for density calculations which is varied between 1 and 1.5km in Cat Tien National Park, but did not extrapolate for the whole area. Result from the same study in Cat Tien estimated approximately 480 individuals in Nam Cat Tien and Cat Loc sectors (Nguyen Xuan Dang et al. 2005). Hughes reported at least eight groups of gibbon existing in Chu Yang Sin NP (Birdlife International, 2010) but this figure may be a significant underestimate because of limited survey effort. In Bidoup Nui Ba NP, Mahood et al. (2009) recorded at least 15 groups in nine subzones and Luu Hong Truong and Le Khac Quyet (2010) recorded 10 groups in another four sub-zones. Mahood et al. (2009) also recorded one group in Da Nhim watershed protection forest, two groups in D’ran watershed protection forest, and two groups in Don Duong State Forest Enterprise. Nguyen Xuan Dang and Osborn (2004) reported that Loc Bac SFE, a contiguous forest block that stretches from CTNP east along the Dong Nai River catchment to Ta Dung NR had at least 4-5 groups recorded in two compartments.
In Vinh Cuu NR, a current survey conducted by the nature reserve staff showed that the yellow-cheeked crested gibbons are expanding their distribution area to the south which is dominated by secondary evergreen forest (Nguyen Hoang Hao pers.com. 2010). This means that gibbons could naturally redistribute to areas of former distribution if human disturbance is reduced. There was no encounter of gibbons during our survey so the average group size remains unknown in Ta Dung NR. Other studies on group size of the yellow-cheeked crested gibbon showed that they live in families with average of 4 individuals (Geissmann et al. 2000). Estimated total individuals (less lone individuals) based on group size of 4 individuals was 47.8 (95% CI 31.5 – 72.8). This population is quite small compared to known population of the species in other areas. This implies that efforts to conserve the yellow-cheeked crested gibbons in Vietnam should be focused on the Central Highlands or southern lowland areas like the Cat Tien-Vinh Cuu complex and Bu Gia Map NP because these areas are supporting viable populations.
It is obvious that the yellow-cheeked crested gibbon in Ta Dung NR faces high threats of hunting and habitat loss and disturbance. More than 1000 HHs are almost totally dependent on the reserves resources for 3-4 months of the year and place a high pressure on biodiversity in general and the gibbon in particular (Ta Dung NR, 2009a). There are 210 households of H’Mong
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ethnic minority living inside the nature reserve (114 HHs) and in the buffer-zone (96HHs). Most men of the H’Mong ethnic minority own hand-made guns and hunting in the reserve is quite common. The management board of Ta Dung NR assessed this threat as the second priority for action.
The reserve was established after the Dong Nai #3 hydropower plant was approved and one of the purposes of the reserve is to protect the water catchment of the Dong Nai #3 hydropower dam. The Da Dung River was blocked earlier this year leading to more than 800ha of forest being inundated. Because the national road connecting Dak Nong and Lam Dong was also inundated, a new road is being built through the nature reserve which has removed an additional several hundred hectares of forest. All people who live inside area inundated by the new dam have moved to other areas and the demand for land for resettlement and cultivation again poses a significant threat on the forest of Ta Dung NR.
Non-timber forest product collection is still going on in the reserve. Even though we recorded NTFP collection at only one listening post, the management board of Ta Dung NR informed us that people often go to the forest and collect bamboo shoots, medicinal plants, honey and especially some wild fruits that are also used by gibbons, such as velvet tamarind (Dialium cochinchinensis), Xerospermum spp., Scaphium macropodium, and wild rambutan (Nephelium spp.). People tended to cut trees or branches to collect more fruits leading to direct food competition and low fruit production in the following years.
Summary and recommendations
We detected eight separate gibbon groups/individuals in the surveyed areas. The total number of gibbons groups within Ta Dung NR was estimated to be approximately 12 groups (excluding lone individuals). Population size of gibbons in groups in Ta Dung NR was estimated between 31.5-72.8 individuals. Most groups are confined to Mount Ta Dung.
Habitat loss and hunting pose serious threats to the yellow-cheeked crested gibbons in Ta Dung NR. While infrastructure development is creating significant habitat loss, guns are identified as the main tool used for hunting. NTFP collection and forest fires are also considered as significant threats to wildlife in general and gibbons in particular.
The current status of the yellow-cheeked crested gibbon population in Ta Dung NR seems to be at risk. A rehabilitation program should be implemented to improve gibbon habitat in the northern part of the reserve by planting wild fruit trees instead of high economic value trees. The management board of Ta Dung NR should cooperate with local authorities to confiscate guns in the local communities and establish community-based patrol groups for better protection of forest resources.
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References
BirdLife International (2010). The Biodiversity of Chu Yang Sin National Park, Dak Lak Province,Vietnam. Compiled and edited by Hughes, R. BirdLife International in Indochina. Hanoi, Vietnam.
Brickle N, Nguyen Cu, Ha Quy Quynh, Nguyen Tai Tu Cuong & Hoang Van San (1998). The status and distribution of Green Peafowl, Pavo muticus, in Dak Lak province, Vietnam. Birdlife International - Vietnam Programme and IEBR, Hanoi.
Brockelman WY, Ali R (1987). Methods of surveying and sampling forest primate populations. In: Marsh CW, Mittermeier RA, editors. Primate conservation in the tropical rain forest. New York: Liss. p 23–62.
Brockelman WY and Srikosamatara S (1993). Estimating density of gibbon groups by use of the loud songs. American Journal of Primatology 29:93–108.
Cheyne SM, Thompson CJH, Phillips AC, Hill RMC and Limin SH (2008). Density and population estimate of gibbons (Hylobates albibarbis) in the Sabangau catchment, Central Kalimantan, Indonesia. Primates 49:50–56.
Dang Huy Huynh, Pham Trong Anh, Le Xuan Canh, Nguyen Cu, Dang Thi Dap, Nguyen Xuan Dang, Hoang Minh Khien, Nguyen Van Sang, Tran Van Thang, Dang Huy Phuong, Tran Ngoc Ninh and Ha Van Tue (1998). Report on the result of field survey on biodiversity of Ta Dung forest, Dak Nong district, Dak Lak province. Hanoi: Institute of Ecology and Biological Resources (in Vietnamese).
Dang Huy Huynh, Le Xuan Canh, Nguyen Xuan Dang, Hoang Minh Khien, Pham Trong Anh, Tran Van Thang and Dang Huy Phương (2010). Mammalian Fauna of Mount Ta Dung, Dak Nong District, Dak Lak Province, Journal of Biology 22A, 1B (2000):99 (in Vietnamese).
Duckworth JW, Timmins R, Anderson GQA, Thewlis RM, Nemeth E, Evans TD, Dvorak M and Cozza KEA (1995). Notes on the status and conservation of the gibbon Hylobates (Nomascus) gabriellae in Laos. Tropical Biodiversity 3:15-27.
Geissmann T, Trinh Dinh Hoang, La Quang Trung2, and Tallents L (2007). A brief survey for crested gibbons in Bach Ma National Park, central Vietnam. Gibbon Journal 3:43-49.
Geissmann T, Nguyen Xuan Dang, Lormée N, Momberg F (2000). Vietnam Primate Conservation Review 2000. Part 1: Gibbons. Fauna & Flora International – Indochina Programme, Hanoi.
Geissmann T, Nguyen Manh Ha, Rawson B, Timmins R, Traeholt C & Walston J (2008). Nomascus gabriellae. In IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1. Accessed on Oct.5th 2010, Available at http://www.iucnredlist.org
Gray TNE, Phan C and Long B (2010). Modelling species distribution at multiple spatial scales: gibbon habitat preferences in a fragmented landscape. Animal Conservation 2010:1-9.
Jiang XL, Luo ZH and Zhao SY (2006). Status and distribution patterns of black crested gibbon (Nomascus concolor jingdongensis) in Wulian Mountains, Yunnan, China: implications for conservation. Primates 47: 264-271.
15
Kenyon MA (2007). The ecology of the golden-cheeked gibbon (Nomascus gabriellae) in Cat Tien National Park, Vietnam. PhD Dissertation, University of Cambridge, Cambridge.
Kenyon MA, Chivers D and Vo Thanh Binh (2010). Home range size and density of yellow-cheeked gibbons (Nomascus gabriellae) in different forest types within Cat Tien National Park, Vietnam. In: Nadler T, Rawson BM, Van Ngoc Thinh (eds) Conservation of Primates in Indochina. Frankfurt Zoological Society and Conservation International, Hanoi, p197-210.
Luu Hong Truong and Le Khac Quyet (2010). Surveys of important habitats and species as a basis for developing ecologically sound Benefit Sharing Mechanisms. Technical report to Center for Biodiversity and Bidoup Nui Ba National Park, Hochiminh City, Vietnam.
Mahood SP, Le Trong Trai, Tran Van Hung and Le Van Hung (2009). Identification, planning and management of forest of high conservation value: final consultancy report. BirdLife International Vietnam Programme, Hanoi, Vietnam.
Nguyen Xuan Dang, Nguyen Hoang Hao, Phan Duy Thuc, Nguyen Thi Ngoc Thin, Nguyen Dinh Quoc Viet, Nguyen Tran Vy and Nguyen Van Thanh (2005). The status of the Golden Cheeked gibbon population (Nomascus gabriellae) in Cat Tien National Park and raising local awareness through conservation education. Technical report to US Fish & Wildlife Services and Cat Tien National Park, 44 pages.
Nguyen Xuan Dang and Osborn T (2004). Biodiversity and Socio -economic Assessment of Loc Bac State Forest Enterprise, Loc Bac Province,Vietnam. WWF Cat Tien National Park Conservation Project, Hanoi.
Nijman V and Menken SBJ (2005). Assessment of census techniques for estimating density and biomass of gibbons (Primates: Hylobatidae). The Raffles Bulletin of Zoology 53:169–179.
O’Brien TG, Kinnaird MF, Nurcahyo A, Iqbal M and Rusmanto M (2004). Abundance and distribution of sympatric gibbons in a threatened Sumatran rain forest. International Journal of Primatology 25:267–284.
Phan Chana and Gray T (2009). The status and habitat of yellow-cheeked crested gibbon Nomascus gabriellae in Phnom Prich Wildlife Sanctuary, Mondulkiri. WWF Greater Mekong - Cambodia Country Programme.
Phan Chana and Gray T (2010). The status and habitat of yellow-cheeked crested gibbon Nomascus gabriellae in Phnom Prich Wildlife Sanctuary, Mondulkiri, Cambodia. In: Nadler T, Rawson BM, Van Ngoc Thinh (eds) Conservation of Primates in Indochina. Frankfurt Zoological Society and Conservation International, Hanoi, p79-90.
Pilgrim JD, Nguyen Xuan Vinh, Nguyen Xuan Dang, Polet G, Thai Truyen, Tordoff AW, Tran Huy Manh, and Peters J (Eds.) (2007). Biological Assessment of the Dong Nai River Basin Conservation Landscape, Vietnam. Unpublished draft report, 19th October 2007.
Rawson, BM (2004). Voicalisation patterns in the yellow-cheeked crested gibbon (Nomascus gabriellae). In: Nadler T, Streicher U, Ha Thang Long (eds) Conservation od Primates in Vietnam. Frankfurt Zoological Society, Hanoi, p130-136.
Rawson BM (2010). The use and abuse of gibbon survey techniques: Shortcomings of auditory survey techniques. In: Nadler T, Rawson BM, Van Ngoc Thinh (eds) Conservation of Primates in Indochina. Frankfurt Zoological Society and Conservation International, Hanoi, p253-258.
16
Rawson B, Clements T, Nut Meng Hor (2009). Status and Conservation of yellow-cheeked Crested Gibbons (Nomascus gabriellae) in the Seima Biodiversity Conservation Area, Mondulkiri Province, Cambodia. In: Lappan S. and Whitaker DM The Gibbons: New Perspectives on Small Ape Socioecology and Population Biology (Eds), Springer, New York, p387-408.
Ta Dung Nature Reserve (2009a). Social Screening Report. Technical report to the Vietnam Conservation Fund, Hochiminh City, Vietnam.
Ta Dung Nature Reserve (2009b). Conservation Needs Assessment. Technical report to the Vietnam Conservation Fund, Hochiminh City, Vietnam.
Traeholt C, Roth Bunthoen, Rawson BM, Mon Samuth, Chea Virak, and Sok Vuthin (2005). Status Review of Pileated Gibbon, Hylobates pileatus and Yellow-cheeked Crested Gibbon, Nomascus gabriellae, in Cambodia. Fauna and Flora International, Indochina Programme, Phnom Penh.
Van Ngoc Thinh, Mootnick AR, Vu Ngoc Thanh, Nadler T and Roos C (2010a). A new species of crested gibbon, from the central Annamite mountain range. Vietnamese Journal of Primatology 1: 1-12.
Van Ngoc Thinh, B. Rawson, C. Hallam, M. Kenyon, T. Nadler, L. Walter, and C. Roos (2010b). Phylogeny and distribution of crested gibbons (genus Nomascus) based on mitochondrial cytochrome b gene sequence data. American Journal of Primatology 72:1047-1054.
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Annexes Annex 1 List of participants
No Name Institution/address Responsibility
1 Hoang Minh Duc Center for Biodiversity and Development (CBD) Team leader
2 Trần Văn Bằng CBD Investigator3 Vũ Long CBD Investigator4 Đinh Hoàng Dũng CBD Investigator5 Nguyễn Hào Quang CBD Investigator6 Nguyễn Thế Trường An University of Science, HCMC Investigator7 Nguyễn Thành Trung University of Science, HCMC Investigator8 Nguyễn Viết Ngọc Tà Đùng technical staff Assistant investigator9 Hoàng Thanh Lương Tà Đùng technical staff Assistant investigator
10 Cao Văn Hào Tà Đùng technical staff Assistant investigator10 Nguyễn Văn Nên Tà Đùng technical staff Assistant investigator11 Trần Quang Vinh Tà Đùng technical staff Assistant investigator19 Lê Phước Thành Tà Đùng technical staff Assistant investigator20 Bùi Đình Thắng Tà Đùng technical staff Assistant investigator25 Phạm Minh Đức Tà Đùng technical staff Assistant investigator17 Huỳnh Quang Nam Forest ranger, station #4 Assistant investigator26 Nguyễn Hữu Toàn Forest ranger, station #3 Assistant investigator27 Trần Văn Hậu Forest ranger, station #3 Assistant investigator28 Dương Bá Tân Forest ranger, station #3 Assistant investigator38 Trần Quốc Toàn Forest ranger, station #3 Assistant investigator39 Trần Quốc Trọng Forest ranger, station #3 Assistant investigator29 Ya Thông Local people, Philieng commune Guidance and porter
8 K Têu Local people Đắc Som commune Guidance and porter9 K Bắt Local people Đắc Som commune Guidance and porter
18 K Mơ mil Local people Đắc Som commune Guidance and porter13 K Rát Local people, Philieng commune Guidance and porter14 K Klong Local people, Philieng commune Guidance and porter21 K Bang Local people, Philieng commune Guidance and porter22 K' Lêu Local people, Philieng commune Guidance and porter23 K Bloi Local people, Philieng commune Guidance and porter24 K Hai Local people, Philieng commune Guidance and porter30 Nông Văn Tính Local people, Philieng commune Guidance and porter31 Đỗ Văn Huy Local people, Philieng commune Guidance and porter32 Ka Tình Local people, Philieng commune Guidance and porter33 Hà Toàn Local people, Philieng commune Guidance and porter34 Ka Phước Local people, Philieng commune Guidance and porter35 Ka Tiêng Local people, Philieng commune Guidance and porter36 Ka Pát Local people, Philieng commune Guidance and porter37 Ka Chong Local people, Philieng commune Guidance and porter
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Annex 2 Details of listening posts at Ta Dung NR
Post # UTM N UTM E Elevation
(m) Habitat Human Disturbance Name of listener Note B12 1317498 177983 1149 Evergreen Hunting Luong,Trung B14 1315524 177796 1188 Evergreen Hunting Quang B11 1317830 176203 1186 Evergreen Hunting Bang B13 1316421 175455 1122 Evergreen Hunting An B33 1320789 177388 1004 Evergreen +Bamboo Hunting Bang B31 1323078 174454 1010 Evergreen +Bamboo Hunting An B34 1319306 175103 979 Evergreen +Bamboo Hunting Quang B32 1321402 175449 877 Evergreen +Bamboo Hunting Hao, Duc AD1 1308649 176712 1165 Evergreen Hunting+ Logging clearing Hau, Dung AD2 1310128 177928 1329 Evergreen Hunting+ Logging clearing Dung AD3 1312726 180745 1447 Evergreen Hunting+ Logging clearing Dung AL1 1309985 175639 1506 Evergreen Hunting+ Logging clearing Long AL2 1308389 174777 1308 Evergreen Hunting+ Logging clearing Long AL3 1311373 179236 1390 Evergreen Hunting+ Logging clearing Long AH1 1314278 180207 1290 Evergreen Hunting+ Logging clearing Hau AT1 1316272 180240 1244 Evergreen Hunting+ Logging clearing Tan B21 1314742 173680 1058 Bamboo Hunting + NTFP collection Long B23 1313043 174121 1227 Evergreen Hunting Bang B22 1314430 175918 1278 Evergreen Hunting Bang, Long
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Annex 3 Detailed information of gibbon calling records at Ta Dung NR
Coordinates (UTM-WGS84 – P49)
Nr
Listening post
number UTM - N UTM - E survey period Elevation
(m) Listener Day
order Start time End time
Solo/ duet
Distance(m)
Compass bearing
Group number
Weather of the day
Weather of previous
night 1 B12 1317498 177983 07-11/10 1149 Luong,Trung 1 6:23:00 6:30:00 duet 600 90 1 2a, 3b no rain
2 B12 1317498 177983 07-11/10 1149 Luong,Trung 2 - - 1a, 3b Rain
3 B12 1317498 177983 07-11/10 1149 Luong Trung 3 - - 2a, 3b rain
4 B14 1315524 177796 07-11/10 1188 Quang 1 5:24:00 5:30:00 solo/M 500 50 2 2a, 3b no rain
5 B14 1315524 177796 07-11/10 1188 Quang 2 - - 1a, 3b Rain
6 B14 1315524 177796 07-11/10 1188 Quang 3 - - 2a, 3b Rain
7 B11 1317830 176203 07-11/10 1186 Bang 1 - - 2a, 3b no rain
8 B11 1317830 176203 07-11/10 1186 Bang 2 - - 1a, 3b Rain 9 B11 1317830 176203 07-11/10 1186 Bang 3 - - 2a, 3b Rain 10 B13 1316421 175455 07-11/10 1122 An 1 - - 2a, 3b no rain 11 B13 1316421 175455 07-11/10 1122 An 2 - - 1a, 3b Rain 12 B13 1316421 175455 07-11/10 1122 An 3 - - 2a, 3b Rain 13 B33 1320789 177388 12-15/10 1004 Bang 1 - - 2a, 3b Rain 14 B33 1320789 177388 12-15/10 1004 Bang 2 - - 1b,3a Rain 15 B31 1323078 174454 12-15/10 1010 An 1 - - 2a, 3b Rain 16 B31 1323078 174454 12-15/10 1010 An 2 - - 1b,3a Rain 17 B34 1319306 175103 12-15/10 979 Quang 1 - - 2a, 3b Rain 18 B34 1319306 175103 12-15/10 979 Quang 2 - - 1b,3a Rain 19 B32 1321402 175449 12-15/10 877 Trung, Hao 1 - - 1b,3a Rain 20 B32 1321402 175449 12-15/10 877 Trung, Hao 2 - - 1b,3a Rain 21 AD1 1308649 176712 7-12/10 1165 Dung, Hau 1 6:30 7:30 duet 400 340 3 2b, 3b Rain
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Coordinates (UTM-WGS84 – P49)
Nr
Listening post
number UTM - N UTM - E survey period Elevation
(m) Listener Day
order Start time End time
Solo/ duet
Distance(m)
Compass bearing
Group number
Weather of the day
Weather of previous
night 22 AD1 1308649 176712 7-12/10 1165 Dung, Hau 2 6:28 7:00 duet 800 320 4 2b, 3b Rain 23 AD2 1310128 177928 7-12/10 1447 Dung 1 5:58 6:14 duet 1000 70 5 2a, 3b Rain 24 AD2 1310128 177928 7-12/10 1447 Dung 2 5:59 6:17 duet 900 65 5 2a, 3b Rain 25 AD2 1310128 177928 7-12/10 1447 Dung 2 6:26 6:35 duet 800 190 6 2a, 3b Rain 26 AD3 1312726 180745 13-15/10 1329 Dung 1 - - 2a, 3b no rain 27 AD3 1312726 180745 13-15/10 1329 Dung 2 - - 1a, 3b Rain 28 AL1 1309985 175639 7-12/10 1506 Long 1 6:06 7:26 duet 600 125 4 2a, 3b Rain 29 AL1 1309985 175639 7-12/10 1506 Long 1 6:17 7:48 duet 600 180 7 2a, 3b Rain 30 AL1 1309985 175639 7-12/10 1506 Long 1 17:37 17:45 duet 400 160 7 2a, 3b Rain 31 AL1 1309985 175639 7-12/10 1506 Long 2 5:18 5:22 duet 800 130 4 2a, 3b Rain 32 AL1 1309985 175639 7-12/10 1506 Long 2 5:55 6:22 duet 700 140 4 2a, 3b Rain 33 AL2 1308389 174777 7-12/10 1308 Long 1 - - 2a, 3b rain 34 AL2 1308389 174777 7-12/10 1308 Long 2 - - 2a, 3b rain 35 AL3 1311373 179236 13-15/10 1390 Long 1 - - 2a, 3b rain 36 AL3 1311373 179236 13-15/10 1390 Long 2 - - 2a, 3b rain 37 AH1 1314278 180207 15-17/10 1290 Hau 1 - - 2a, 3b rain 38 AH1 1314278 180207 15-17/10 1290 Hau 2 - - 2a, 3b rain 39 AT1 1316272 180240 15-17/10 1244 Tan 1 - - 2a, 3b rain 40 AT1 1316272 180240 15-17/10 1244 Tan 2 - - 2a, 3b rain 41 B21 1314742 173680 23-27/10 1058 Long 1 6:13 6:27 duet 800 168 7 2a, 3b no rain 42 B21 1314742 173680 23-27/10 1058 Long 2 - - 1b,3b no rain 43 B23 1313043 174121 23-27/10 1227 Bang 1 6:14 6:30 solo/M 900 21 8 2a, 3b no rain 44 B23 1313043 174121 23-27/10 1227 Bang 2 - - 1b,3b no rain 45 B22 1314430 175918 23-27/10 1278 Bang, Long 1 - - 2a, 3b rain Note
1 rain 2: no rain 3 windy M: male a heavy rain a: cloudy a strong wind b small rain b: clear b breeze
21
Annex 4 Some photos taken during the training and gibbon survey
Participants at the end of the training
Evergreen forest on Mount Ta Dung
22
Mixed broadleaf and bamboo forest
A hunting camp on Mount Ta Dung