INTRODUCTION
The Central Annamite Mountain Range in Vietnam is recognized as a biodiversity hotspot of global significance by WWF This region is home to numerous rare and endemic species, including the recently rediscovered Saola (Pseudoryx nghetinhensis), Giant muntjac (Muntiacus vuquangensis), and Truong Son muntjac.
(Muntiacus truongsonensis), Grey-shanked douc langur (Pygathryx cinerea), Red- shanked douc langur (Pygathrix nemaeus), and Asian elephant (Elephas maximus) as well as the Northern yellow-cheeked gibbon (Nomascus annamensis)
The Northern yellow-cheeked gibbon, identified as a new species of Hylobatidae in 2010 by Van Ngoc Thinh et al., was previously misclassified alongside N gabriellae and N siki due to similarities in morphology and vocalizations However, distinct differences in their calls and mitochondrial DNA led to the recognition of N annamensis as a unique species This gibbon is endemic to the Indochina region, specifically recorded in central Vietnam, Laos, and Cambodia Despite its known distribution, detailed information regarding its exact range, occurrence in protected areas, and population size remains insufficient Like other crested gibbons, N annamensis faces threats from illegal hunting and habitat loss due to logging and agricultural expansion, highlighting the urgent need for conservation efforts.
Gibbons are often elusive and challenging to spot due to their low visibility and unpredictable reactions to humans However, in optimal conditions, their distinctive calls can be heard from distances of up to 3 kilometers.
Gibbon species can be detected through their distinct calls, traditionally studied by human surveys Surveyors document their observations of gibbons, which is a straightforward and reliable method However, the accuracy of this data heavily relies on the expertise of the surveyors in identifying gibbon groups and individuals Additionally, surveyors may need to traverse large areas to locate these groups, and their presence can influence the behavior of the gibbons.
Bioacoustics analysis is an innovative technique for tracking the presence, distribution, movement, and behavior of terrestrial animals, including gibbon species (Wilson et al 2014) This method relies on both hardware and software components; the hardware consists of recording equipment to capture animal sounds, while the software involves computer programs designed to input, interpret, and analyze the recorded audio files.
In order to contribute to N annamensis conservation, I conducted a study titled “A survey for Northern yellow-cheeked gibbon ( Nomascus annamensis ) in
Central Annamite Mountain Range of Vietnam using bioacoustics method”
The study aims to gather information on the population of N annamensis in three protected areas of the Central Annamite Mountain Range in Vietnam: Hue Special Nature Reserve, Bach Ma National Park, and Quang Nam Special Nature Reserve The specific objectives include assessing the number of N annamensis groups present in these areas.
(2) and assessing detailed information of N annamensis group size and structure
LITERATURE REVIEW
Gibbon status in Vietnam
Vietnam hosts a variety of gibbon species, ranging from subtropical forests in the north to tropical monsoon lowland forests in the south The presence of gibbons serves as a key indicator of the country's biodiversity and overall environmental health To assess their conservation status, a review was conducted by Geissmann et al.
In a recent study by Rawson et al (2011), a comprehensive survey was conducted to gather reliable records of gibbons across various sites in Vietnam known to host these primates The findings contribute valuable insights into the distribution and status of gibbons in the region.
(2011) has provided a comprehensive information on the status of gibbon in Vietnam According to Rawson et al
(2011), all gibbons in Vietnam are classified into the genus of crested gibbon Nomascus Totally, there are seven species of Nomascus, all located in the eastern Mekong River in Cambodia,
China, Laos and Vietnam, six of which are found in Vietnam The species in
Vietnam being, from north to south orderly are Eastern black gibbon
The article discusses various species of gibbons, including Nomascus nasutus, the Western black gibbon (Nomascus concolor), the Northern white-cheeked gibbon (Nomascus leucogenys), the Southern white-cheeked gibbon (Nomascus siki), the Northern yellow-cheeked gibbon (Nomascus annamensis), and the Southern yellow-cheeked gibbon (Nomascus gabriellae), highlighting their unique characteristics and classifications.
Figure 1 Distribution of the six
Vietnam is home to the highest number of Nomascus species globally, yet the gibbon population is facing a critical crisis, reflecting broader trends in wildlife decline across the country.
Northern yellow-cheeked gibbon (Nomascus annamensis)
Nomascus annamensis, the latest identified species of Nomascus gibbons, was described by Van Ngoc Thinh et al in 2010 This species was often misidentified as either N gabriellae or N siki due to its similar morphological and vocal characteristics.
Adult N annamensis clearly differ from N leucogenys and N siki
Males of the species exhibit black fur with cheek whiskers that vary in color from yellowish to deep orange and light brown, while females are characterized by their golden yellow fur and a distinctive brown to black patch on their heads.
Figure 2 Northern yellow-cheeked gibbon (Nomascus annamensis) a) Adult male; b) Adult female
Source: Endangered Primate Rescue Center (EPRC)
According to complete mitochondrial cytochrome b gene sequence data (Fig
3), N annamensis is closest related to N gabriellae In specifically, N annamensis‟s gen (n = 22) differs from N gabriellae (n = 69), N siki (n = 32) and
Figure 3 Phylogenetic relationships among crested gibbon species base on complete mitochondrial cytochrome b sequence data
Source: Van Ngoc Thinh, et al 2010
By using a discriminant function analysis, Van Ngoc Thinh et al (2010) demonstrated the differences in several acoustic feature such frequency and tempo (Fig 4) from the other crested gibbon species
Figure 4 Spectrograms of N leucogenys, N siki, N annamensis and N gabriellae
Source: Van Ngoc Thinh et al 2010
- English name: northern yellow-cheeked gibbon
- French name: Gibbon à joues jaunes du Nord
- German name: Nửrdlicher Gelbwangen Schopfgibbon
According to Van Ngoc Thinh's review, N annamensis is found in the central and southern provinces of Laos, specifically in Attapu, Champasak, Salavan, Savannakhet, and Xekong Additionally, it occurs north of the Srepok River, around 13°30' N, in the regions of Stung Treng and Rattanakiri.
Provinces of Cambodia and from approximately the Thach Han River (about 16°40‟ - 16°50‟ N) in Quang Tri Province to the Ba River (about 13°00‟ - 13°10‟N) in Gia Lai and Phu Yen Provinces in Vietnam
N annamensis occurs in broadleaf evergreen and semi-evergreen forest They spent the majority of their time feeding on fruit, followed by young leaves, flowers and mature leaves (Hon et al 2018)
The Northern yellow-cheeked gibbon was described as a new species, thus is yet to be evaluated for the IUCN Red List and the 2007 Vietnam Red Data Book
CITES Appendix I - this species is threatened with extinction and international trade is permitted only in exceptions circumstances
Nomascus annamensis in Vietnam
Nomascus annamensis was first identified in Vietnam by Geissmann in 2000, initially classified as N siki and N gabriellae It wasn't until 2010, following studies of its vocalizations and genetics, that N annamensis was recognized as a distinct species of crested gibbon By that time, its presence had been documented in at least nine provinces, encompassing 11 protected areas, two proposed nature reserves, and two watershed management zones.
As the results of Nguyen Manh Ha‟s study (2009), the largest known population of N annamensis in Vietnam was found in Dak Rong and Phong Dien
Quang Tri and Thua Thien Hue Provinces are home to significant nature reserves that have undergone extensive biodiversity surveys and monitoring, making them areas with the largest known populations of various species Additionally, Song Thanh and Ngoc Linh Nature Reserves in Quang Ngai may also harbor important populations of N annamensis, highlighting the ecological significance of these regions.
Quang Nam Provinces; and Kon Ka Kinh National Park, Kon Cha Rang Nature Reserve and surrounding production forests in Kon Tum Province
The presence of N annamensis has been verified in eight protected areas across central Vietnam, including Bac Huong Hoa NR with 10 groups, Dakrong NR with 7 groups, Phong Dien NR with 10 groups, Bach Ma NP hosting 13 groups, Hue SNR with 8 groups, Song Thanh NR with 2 groups, Chu Mom Ray NP with 14 groups, and Kon Ka Kinh NP with 7 groups (Van Thien et al 2017).
Figure 5 The distribution of N.annamensis in Vietnam
N annamensis in Vietnam faces significant threats from illegal hunting and habitat loss, primarily driven by commercial demand for the pet trade, zoos, and traditional medicine This species is particularly sensitive to habitat changes, with forest loss and fragmentation caused by both legal and illegal logging, agricultural conversion, and infrastructure development, including roads and hydroelectric dams These activities severely impact the population of N annamensis across its national range.
Nomascus annamensis in Hue SNR, Bach Ma NP and Quang Nam SNR
Despite the incomplete survey coverage and the uncertainty surrounding the total gibbon population, it is estimated that at least 14 gibbon groups inhabit Hue Special Nature Reserve (Van Ngoc Thinh et al 2007; Nguyen Quang Hoa Anh et al 2010).
In Bach Ma National Park, Eames and Robson estimated the gibbon population to be between 23 and 30 individuals based on surveys conducted in 1990-1991 However, due to incomplete survey coverage, the exact total population of gibbons in the park remains unknown.
In 2001, a study identified eight gibbon groups, including two solitary males, within a 600-hectare area (Tallents et al 2001) By 2005, the number of gibbon groups increased to five, observed in a larger area of 1,000 hectares (Van Ngoc Thinh et al 2010).
The Quang Nam Saola Nature Reserve is believed to host N annamensis, with 30 gibbon groups previously recorded in 2005 across 13 locations nearby (Hoang et al 2005) Additionally, gibbons were documented in Dong Giang District and surrounding areas in 1997 (Wikramanayake and Vũ 1997) However, the current status of gibbon populations in the reserve remains uncertain, indicating that their numbers may be minimal.
Nomascus annamensis vocalization
Gibbons, alongside humans, are the only hominoids in which both sexes participate in complex vocal displays known as songs These songs are produced by both individual gibbons and monogamous pairs, emphasizing their territorial nature Additionally, the vocal repertoire of gibbons is distinctively sex-specific.
Figure 6 Typical male‟s (left) and female‟s (right) spectrogram showing the vocalization of gibbons
Adult N annamensis males exhibit a vocalization structure characterized by a distinctive "staccato" note and a "multi-modulation" phrase, known as the coda phrase The "staccato" notes are subtle and produced in short, irregular series, while the multi-modulation phrases represent dominant acoustic structures (Haimoff 1984) In contrast, adult females produce only "great call" phrases or their fragments.
The "great call" of gibbons consists of 5-13 notes, categorized into "oo" notes, "bark" notes, and a "twitter" phase The "oo" phase features long notes with a gradual frequency increase of ≤1 kHz/s, while "bark" notes are characterized by a rapid frequency rise of >1 kHz/s Following the peak of the bark notes, the sound transitions into the twitter phase, which is often not measured due to its limited range and faint visibility on sonograms Male gibbon songs are typically shorter, more consistent, and range from 1 to 2 kHz, whereas female gibbon songs are longer and exhibit a larger amplitude, starting from 0.5 kHz.
3 kHz Accordingly, differences in male and female gibbon songs of mature individuals can be easily determined
Initially, the "great call" was believed to be exclusively produced by adult female gibbons (Geissmann 2002) However, recent studies have shown that immature male gibbons can also emit sounds similar to the "great call" (Koda et al 2014) This finding highlights the need for careful identification of group structures Notably, the "great calls" of male offspring are shorter, begin at a higher pitch, and conclude at a lower pitch compared to those of their mothers.
Figure 7 Representative spectrogram showing the parameters measured: Start F
The study examines the frequency at call onset and offset, along with the delay and number of syllables in the "great calls" of both mother and juvenile male The analysis distinguishes between syllables, with black numbers representing the mother's syllables and red numbers indicating those of the juvenile male The organization of these calls is illustrated, with dashed lines depicting the juvenile's notes—N(J) for juvenile notes and T(J) for juvenile twitter—while solid lines represent the mother's notes, including O for "oo" notes and B for other variations.
METHOD
Study area
In my research, I utilized data collected by WWF - Vietnam in 2016 from three adjacent protected areas: Thua Thien Hue Special Nature Reserve, Bach Ma National Park, and Quang Nam Special Nature Reserve, which are located along the border of Thua Thien Hue and Quang Nam provinces.
Bach Ma National Park is located in the southern edge of
Thua Thien Hue Province in central
Vietnam The area of the park is located within the coordinate of
107 o 53‟E In order to conserve the rich forest between northern and southern Vietnam, this national park was established in 1991 (Lan et al 2002)
The park area is about 220 km 2 , of which 169 km 2 is forest land and 51 km 2 have no forest cover The forested area includes
27 km 2 rich forest, 59 km 2 medium forest, 65 km 2 poor forest and the rest area is young forest (Thinh et
Figure 8 Bach Ma National Park, Hue and
Quang Nam Saola Nature Reserve location
Source: Author al 2002) Because of human affect, no primary forest now remains in Bach Ma NP
Bach Ma National Park, located in the central Annamite Mountains, features a high mountain ridge that extends from the Laotian border to the East Sea, serving as a biogeographical boundary between northern and southern Vietnam's diverse flora and fauna With its steep and rugged terrain, the park boasts several peaks exceeding 1,000 meters, including the highest peak, Mount Bach Ma, which rises to 1,448 meters Due to its unique topography, Bach Ma National Park is recognized as a critical area for biodiversity conservation.
More specifically, the park is home to a diverse range of species, including 2,373 species of plants and fungi and 2,115 species of animals (Keo & Thien An,
Bach Ma National Park is recognized as a vital habitat in Vietnam, hosting significant populations of nationally important primates, including the red-shanked douc langur (Pygathrix nemaeus) and the North yellow-cheeked crested gibbon (Nomascus annamensis).
(Robson et al 1991) However, the current status of many of these species at the national park is unclear
Established in 2010 and 2011, the Hue and Quang Nam Saola Nature Reserves aim to protect the endangered Saola (Pseudoryx nghetinhensis) in Vietnam Located within the coordinates of 16°03′-16°09′ N and 107°25′-107°39′ E, the Hue Nature Reserve spans 15,500 hectares, featuring a significant expanse of primary natural forest in the Central Annamite Mountains This reserve is home to over 1,200 species of flora and fauna, including several rare and endemic species such as Pseudoryx nghetinhensis, Muntiacus truongsonensis, Muntiacus vuquangensis, and Nesolagus timminsi.
Quang Nam Special Nature Reserve spans approximately 16,500 hectares, encompassing four towns in the Tay Giang and Nam Giang districts This nature reserve serves as a crucial habitat for numerous rare wildlife and plant species that are recognized in both Vietnam and the IUCN Red Lists.
Bach Ma National Park and Hue, along with the Quang Nam Saola Nature Reserve, create a continuous protected landscape that spans from the Vietnamese coast to the Xe Sap National Biodiversity Conservation Area in Laos This expansive area serves as a vital landscape corridor, enhancing resilience against the impacts of development, climate change, and human pressure.
Data collection
The data were collected in period of 90 days from August to November,
In three protected areas, 30 locations were selected to perform recording (10
(Fig 9) Each location was continuously recorded in 3 days by small Sony recorders
Point surveying was conducted alongside the installation of automatic recorders and nearby recorder locations A team of 3 to 5 WWF staff members established listening and observing posts at each site, with surveys carried out over three consecutive days These surveys commenced at 5:00 AM and concluded at 10:00 AM to coincide with the peak singing times of the gibbons The survey teams possessed the necessary knowledge and skills to accurately locate the calling groups by mapping the angles and estimating the distances to the gibbon groups.
During hearing and observing, all information of gibbon groups was recorded in the data sheet as below:
DATA SHEET OF GIBBON SURVEY
Protected Area: ………… Station Number: ……… Date: ………
Figure 9 Study area and recorder locations in three protected areas in 2016
Sound analysis
Determining number of gibbon group
Various software options are available for displaying sound sonograms, including Avisoft SASLab Pro, Avisoft SASLab Lite, Avisoft SASLab Recorder, Audacity, and Luscinia Among these, I selected Raven Pro due to its simplicity and wide range of features.
RAVEN software, developed by The Cornell Lab of Ornithology, is a comprehensive bioacoustics research program designed for the acquisition, visualization, measurement, and analysis of sound It comprises three components: Raven Pro, Raven Exhibit, and Raven Lite Raven Pro offers an intuitive interface for opening sound files and navigating through waveform and spectrogram views, allowing users to focus on specific sound segments Raven Exhibit is tailored for public displays and educational outreach in venues like science museums and zoos, while Raven Lite enables users to record, save, and visualize sounds as spectrograms and waveforms Each bird species produces unique sounds characterized by distinct frequency ranges, pitch modulation speeds, vocabulary sizes, and durations, which are represented in their respective spectrograms.
Figure 10 Sound windows in Raven software
The analyzing process was performed as follow:
- Converting sound data file obtained in the field to a typical format as WAV
- Launching Raven Pro Interactive Sound Analysis Software
- Running the program and analysis
The spectrogram of record sound file were carefully check Whenever a gibbon call was detected, it would be heard again to be surely confirmed
The number of gibbon group and group structure could be determined based on the differences in the vocalization of mature males and females shown in spectrograms
Gibbon songs can be difficult to analyze due to their distance, making it challenging to accurately count the number of calls Consequently, only the minimum group sizes can be reported based on the individuals heard calling Over three days of surveys, the maximum number of gibbon groups detected each day serves as an estimate for the total gibbon population at a site.
RESULTS
Gibbon calls detected
The number and percentage of recording posts with gibbon calls is highest in Hue SNR and lowest in Quang Nam SNR (Table 1 and Fig 11, 12, 13)
Table 1 Number of recording posts with gibbon calls
Protected areas Number of recording posts
Number of recording posts with gibbon calls
Percentage of recording posts with gibbon calls
Figure 12 Recording locations with N annamensis calls in Bach Ma NP
Figure 13 Recording locations with N annamensis calls in Quang Nam SNR
During 90 survey days , with total of 19 recording posts (with gibbon calls), 66 gibbon calls were recorded, in which almost calls are from multi individuals (See Appendix 1)
Because a group could repeat their calls many time, after removing of repeated calls, there were at least 41 N annamensis groups estimated in three protected areas
Hue SNR hold the largest number of gibbon group, followed by Bach Ma NP and Quang Nam SNR (Table 2)
In a comparison of three protected areas, Hue SNR recorded the highest average number of N annamensis groups per location, while Quang Nam SNR had the lowest, with Bach Ma NP falling in between.
Table 2 Number of gibbon group per recording site detected by bioacoustics analysis
Averaged number of gibbon groups
Estimate Standard error Hue SNR
Figure 14 Averaged number of gibbon group per recording site detected by bioacoustics analysis
Hue SNR Bach Ma NP Quang Nam SNR
Gibbon group structure detected
There are 3 types of gibbon group structure including complex group (male(s), female(s) and juvenile (s)), pair (male and female) and solo individuals (one male or female) (Fig 15)
The study identified various gibbon call structures, categorized into complex groups, pairs, and solo individuals Most gibbon groups observed comprised one adult male accompanied by one to three other members.
The study identified "great call singers" within 41 recorded groups, comprising adult females and juvenile members Among these groups, 20 (49%) were classified as gibbon complex groups, 11 (27%) were pairs, and 13 (24%) were solo individuals.
Table 3 The number of gibbon call structure types
Pair (duet) calls Solo calls Total
Figure 16 The percentage of N annamensis group structure types
At least 96 individuals of Northern yellow-cheeked gibbons were identified including 45 males, 43 females and 8 juveniles (Table 4 and Fig 17)
Table 4 N annamensis group structure and averaged group size in three protected areas
Protected areas Number of males
Averaged group size (95% of confidence)
Figure 17 Number of males, females and juvenile N annamensis detected in three protected areas in 2016.
Number of males Number of females Number of juvenile
Hue SNR Bach Ma NP Quang Nam SNR
DISCUSSION
Due to time constraints, not all protected areas in the Central Annamite Mountain Range were surveyed; however, key locations for N annamensis, including Hue SNR, Bach Ma NP, and Quang Nam SNR, were assessed by WWF-Vietnam.
Gibbon calls were documented at nine locations in Hue SNR, seven in Bach Ma NP, and only three in Quang Nam SNR, indicating an uneven distribution of gibbons across these protected areas, particularly in Quang Nam SNR This distribution pattern highlights the relationship between gibbon presence and forest conditions, as these primates thrive in areas with uninterrupted canopy cover.
A total of 66 gibbon calls were recorded, estimating 41 groups and 96 individuals, primarily in Hue Special Nature Reserve (SNR), followed by Bach Ma National Park (NP) and Quang Nam NP The N annamensis population in Hue SNR faces threats from hunting and habitat loss due to highway construction, illegal logging, and gold mining, although it still contains a significant area of primary forest in the Central Annamite Mountains Conservation efforts, including gibbon surveys and ranger training, are underway in the reserve In contrast, Quang Nam SNR has limited undisturbed forest areas, heavily impacted by human activities, and lacks priority for gibbon conservation, resulting in no required surveys Similarly, Bach Ma NP has only 27 km² of forest, with no primary forest present, and illegal hunting remains a critical issue The combined effects of habitat degradation and illegal hunting contribute to the declining N annamensis population in these protected areas compared to Hue SNR.
This study reveals a higher number of gibbon groups in Hue Special Nature Reserve and Bach Ma National Park compared to previous reports, attributed to a more extensive survey scale The increased detection of N annamensis indicates a more representative assessment of the overall population in these areas Conversely, the Northern yellow-cheeked gibbon population in Quang Nam Special Nature Reserve appears to be declining due to habitat loss and adverse human activities.
Gibbons typically form family groups consisting of a bonded male and female, along with their offspring While it has traditionally been thought that gibbons only create monogamous social structures, recent studies indicate that extra-pair copulations can occur In my research, I found that nearly half of the observed groups exhibit complex structures that include both monogamous and extra-pair relationships, while the other half consists of pair and solitary formations The average group size was 2.34 ± 0.15, with the largest group comprising four individuals These findings align with previous research on the social structure of N annamensis, although it's important to note that the estimated group sizes do not account for infants, as they do not vocalize.
With this study, at least 96 individuals including 45 males, 43 females and 8 juveniles were detected It means gender imbalance is not problem of gibbon population in three protected areas
Utilizing sound recorders and sound analysis software allows for precise detection of gibbon group numbers and structures, providing surveyors with more time to analyze gibbon vocalizations compared to traditional field methods While this approach shows promise in assessing gibbon populations, potential errors may arise The effectiveness of this technique is influenced by factors such as recorder quality, weather conditions, and the expertise of the sound analyst.
To conserve the remaining population of N annamensis in Vietnam, it is crucial to protect their habitat and regulate hunting practices Increased funding for species conservation efforts is essential, and further research should be promoted to enhance our understanding of gibbon status across their entire distribution range.
CONCLUSION
Northern yellow-cheeked gibbon calls occurred in 19 recording posts in three protected areas During 90 days of surveying, 66 gibbon calls were recorded
At least 41 groups of N annamensis were recorded, of which 22 groups were located in Hue SNR, 15 groups in Bach Ma NP and 4 groups in Quang Nam SNR
The averaged group number of N annamensis per location of Hue SNR, Bach
Ma NP and Quang Nam SNR orderly are 2.2, 1.5 and 0.4 groups/location
The dominant structure of N.annamensis is complex group structure In total of
41 recorded groups, 20 (49%) were gibbon complex group, 11 (27%) pairs and 10 (24%) solo individuals This result is similar with previous finding of other researchers on gibbon social structure
The group size are 2.36 ± 0.21, 2.40 ± 0.25 and 2.00 ± 0.41 individuals/ group in Hue SNR, Bach Ma NP and Quang Nam SNR respectively
Combining between acoustic analysis result and information on group size and structure, at least 96 individuals of Northern yellow-cheeked gibbons were identified including 45 males, 43 females and 8 juveniles
The most effective solutions for gibbon conservation in these three protected areas include protecting habitat, controlling the hunting, raising fund, and enhancing gibbon status surveys monitoring
This thesis would not have been possible without the invaluable support from the International Master Program at Vietnam National University of Forestry I extend my heartfelt gratitude to my advisor, Assoc Professor Vu Tien Thinh, for his unwavering support and enthusiastic guidance throughout my research and writing process.
Special thanks to WWF-Vietnam for their kindly support, providing data and information to help me complete this study
Sincerely thanks to all of my friends and family who always encourage, and support me during this strenuous time
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APPENDIX Appendix 1: N annamensis group structure detected by acoustic recording analysis
Survey Block ID FC Complex group/ pair/ individual number
Bach Ma NP 57 410 Complex group 1 1 1 3 1
Bach Ma NP 71 427 Complex group 1 2 1 4 1
Bach Ma NP Complex group 2 1 2 0 3
Bach Ma NP Complex group 3 2 2 0 4
Bach Ma NP Complex group 2 1 1 1 3
Quang Nam SNR 25 12 Complex group 1 2 0 3 1
Appendix 2: Number of gibbon groups, groups‟ structure Protected Area
Appendix 3 Some picture of N annamensis, N leucogenys, N siki and N gabriellae
Adult male of N siki Photo Tilo Nadler Adult male of N gabriellae Photo Tilo Nadler
Adult female of N annamensis Photo: Tilo Nadle Adult female of N gabriellae Photo: Tilo Nadler.