Identifying the occurrence and distribution of southern white cheeked gibbon nomascus siki delacour 1951 using autonomous recorders a case study in the khe nuoc trong proposed nature reserve

MINISTRY OF EDUCATIONAND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM NATIONAL UNIVERSITY OF FORESTRY  ABU BAKAR “IDENTIFYING THE OCCURRENCE AND DISTRIBUTION OF SOUTHERN WHITE- CHEEKED GIBBON NOMASCUS SIKI (DELACOUR, 1951) USING AUTONOMOUS RECORDERS: A CASE STUDY IN THE KHE NUOC TRONG PROPOSED NATURE RESERVE’’ MASTER THESIS IN FOREST SCIENCE Hanoi, November 2018 MINISTRY OF EDUCATIONAND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM NATIONAL UNIVERSITY OF FORESTRY  ABU BAKAR “IDENTIFYING THE OCCURRENCE AND DISTRIBUTION OF SOUTHERN WHITE- CHEEKED GIBBON NOMASCUS SIKI (DELACOUR, 1951) USING AUTONOMOUS RECORDERS: A CASE STUDY IN THE KHE NUOC TRONG PROPOSED NATURE RESERVE’’ Major: Forest Science Code: 8620201 MASTER THESIS IN FOREST SCIENCE Supervisor: Assoc Prof Dr Vu Tien Thinh Signature: ………………… Hanoi, Novemeber 2018 ABSTRACT It is necessary to have accurate information on a species occurrence and distribution in order to monitor and protect endangered species While traditional survey methods have several limitations, using automatic recorders in monitoring wildlife provides significant promise for detecting the gibbon sounds because gibbon produce loud and elaborate sounds Autonomous recorder was used to record the gibbon calls and the associated sound analysis software (RAVEN Software) to determine the occurrence and distribution of the Southern white-cheeked gibbons (Nomascus siki) in Khe Nuoc Trong proposed nature reserve The survey was conducted in compartments of the Khe Nuoc Trong proposed nature reserve for 27 days, 53 recording posts were set up in the field and the sounds were recorded for 1-3 consecutive days From recording posts no gibbon call was detected and from 46 recording posts gibbons call was detected The recorders were set up to record the sounds of gibbon in the nature reserve for all the day Gibbons usually produce loud sounds early in the morning that last for 10-30 minutes which starts from 5am to 9am Therefore, data was analyzed from 5am to 9am in the morning The male and female gibbons produce different sounds and have different song structures from which we can recognize them easily In this study 26 gibbon calls were detected from the recordings The gibbon groups are distributed to the west and near the central part of the nature reserve Weather has also a great effect on the gibbon singing which decreases the singing of the gibbon and the gibbon which did not sing while surveying remain undetected The forest of the surveyed area is broadleaf evergreen forest (rich forest, medium forest) which is the best habitat for gibbons The medium to high montane broadleaf evergreen forest contributes the highest percentage of the detected gibbon in the Khe Nuoc Trong proposed nature reserve i TABLE OF CONTENTS ABSTRACT i LIST OF FIGURE iv LIST OF TABLE v INTRODUCTION 1.1 Background 1.2 Goal 1.3 Specific objectives 1.4 Research questions LITERATURE REVIEW 2.1 Occurrence and distribution 2.2 Gibbon in Vietnam 2.3 Distribution of Southern white-cheeked gibbon in Vietnam 2.4 Vocalization of gibbons 2.5 Calling time of gibbon 12 2.6 Factors effecting gibbon call 12 2.7 Using of automatic recorder 13 METHODS 16 3.1 Study area description 16 3.1.1 Location 16 3.1.2 Topography 16 3.1.3 Flora and Fauna 16 3.1.4 Population 17 3.2 Field survey 18 3.3 Data analysis and vocalization analysis Method 21 3.3.1 Sound analysis 21 ii 3.3.2 Effect of weather on the singing behavior of gibbons 21 3.4 Vocalization analysis 22 3.4.1 Duet calls songs of Southern white-cheeked gibbon: 22 3.4.2 Female song of Southern white-cheeked gibbon 23 3.4.3 Male song of southern-white cheeked gibbon 23 RESULT 25 4.1 Gibbon calls detected 25 4.2 Distribution of gibbons in Khe Nuoc Trong proposed nature reserve 26 4.3 Structure of gibbon group 30 DISCUSSION 35 5.1 Occurrence and distribution of white-cheeked crested gibbon in KNT proposed nature reserve 35 CONCLUSION 39 ACKNOWLEDGEMENT 40 REFERENCE 41 APPENDICES 46 iii LIST OF FIGURE Figure 1.1 Spectrograms of the six crested gibbon species of Vietnam 10 Figure.3.1 Flora images of the KNT proposed nature reserve 17 Figure.3.2 Elevation map of Khe Nuoc Trong proposed Nature Reserve, Quang Binh Province, Vietnam in May 2018 18 Figure.3.3 Elevation map of recording posts in the KNT proposed nature reserve in May 2017 19 Figure 3.4 SM3 (Wildlife Acoustic) automatic recorders was attached to the trees in Khe Nuoc Trong proposed nature reserve 19 Figure.3.5 Duet call of the Sothern white-cheeked gibbon, great call is female call and short call is male call 23 Figure 4.1 Frequency distribution of the start time of gibbon song bouts 25 Figure.4.2 Percentage graph of the rain and no rainy days in the survey 26 Figure.4.3 Elevation and comparative map of the gibbon with forest type in Khe Nuoc Trong nature reserve in May 2018 27 Figure.4.4 Elevation and forest type map of the surveyed area with gibbons in the Khe Nuoc Trong nature reserve in May 2018 28 Figure.4.5 Percentage graph of the surveyed area forest 29 Figure.4.6 Elevation and distribution map of gibbon in the KNT proposed nature reserve in May 2018 29 Figure.4.7 Duet call of the southern white-cheeked gibbon from recording site at 5:55am 37 Figure.4.8.Female sonogram of Southern white-cheeked gibbon from recording site at 4:47am 33 Figure.4.9 Male sonogram of the southern white-cheeked gibbon from recording site at 5:35am 34 iv LIST OF TABLE Table.1.1 List of Vietnamese gibbons Table.3.1 Area of each sub-zone in the study area 20 Table.4.1 Percentage graph of the gibbon call detected in each compartment 30 Table.4.2 Structure of the gibbon calls with recorded time 31 v INTRODUCTION 1.1 Background Geographically, Vietnam lies in the southeast Asia with an area of 331.689 km2and extends up to 1,600 km from north to south, along the eastern coast of Indochina from 230 N to 8030' N Altitude varies from the sea level to 3,143 m at the summit of mount Phan Si pan in the extreme north-west of the country (Geissmann, 2000b) Vietnam is rich in the biodiversity and many new species have been discovered by researchers recently Many endangered species are present in Vietnam and their populations are decreasing because of deforestation, hunting, and land encroachment (Geissmann, 2000a) In the north of Vietnam most of the primates which are endangered and critically endangered are found Among these one of the endangered primate is gibbon species which is only found in the north-central of Vietnam in six provinces (Harding, 2012) Gibbon belongs to the family Hylobatidae and is among the most endangered Vietnamese primates Gibbon populations is expected to become extinct faster than other primates (Geissmann et al., 2001) Gibbons are arboreal apes living in the tropical rain forests of south-east Asia (Geissmann, 2000a) The impact of hunting on gibbons in the recent past is undeniable and illustrated by the occurrence of suppressed populations within areas of largely intact habitat, suggesting hunting is a primary threat In some areas of central Vietnam there is no sufficient data available about gibbon species (Nadler et al., 2007a) Monitoring programmes are the main source of information on the population status of species of conservation concern, and have a significant role in setting conservation action priorities The use of monitoring in conservation is important for gibbon because gibbons are facing many problems so to evaluate the species problem and to estimate total population size of gibbons we need to monitoring for gibbons By monitoring we can also identify the change in population size in a region and also helps to find the threats to the species Knowledge of population size is important in research which aimed at understanding interactions between species Monitoring programmes are not only designed to measure change in abundance but also used to estimate density, and by extension population size, if certain assumptions are upheld (Stokes et al., 2010) Monitoring a species may face a lot of difficulties Gibbon is difficult to monitor by the traditional method and lead to a range limitation and often does not give accurate information in the survey Therefore, by not having accurate information resulting in numerous difficulties for conservation (Vinh et al., 2010) The management of the gibbon species requires detailed information on the distribution and abundance which is often hard to obtain Gibbons live in the upper canopy of the forest and are closely associated with closed canopy of broadleaf evergreen forests Gibbons are strongly arboreal and sometimes come to the ground (Sarma et al., 2013) Gibbon moves very quick in the upper canopy of the trees and people rarely see them in the forest Therefore, visual detections of gibbon are very difficult in the field, especially for short survey (Vinh et al., 2010) Human interactions with primates may influence their behavior and using automatic recorders in the field has no direct contact with human observers thus reducing any possible impact of humans on their singing behavior (MuñozDelgado et al., 2004) Using automatic sound recorder is an effective survey method for many reasons First reason is that it is suitable for surveying animals which not sing daily Second reason is less human disturbance in the survey by using automatic recorder than traditional survey Third reason is it‟s beneficial in the difficult areas in the survey and no specialists are needed in the field survey (Thinh et al., 2017) Data could be analyzed easily from the recordings samples and each vocalization clip was then transferred to RAVEN PRO 1.4 sound analysis software (Cornell Lab of Ornithology Bioacoustics Research Program) to create spectrograms and measure attributes of the different vocal types (Cäsar et al., 2012) Many researchers suggested automatic recording is the best way to collect the data on animals in the field Automated acoustic monitoring can be used for studying various taxonomic groups of sound-producing animals and allows the detection of elusive, rare, and threatened species (Collen et al., 2009; Burbidge, A 2017) Gibbons produce a loud and elaborate sound and can be detected by their loud and long song bout (Geissmann and Orgeldinger 2000a; Brockelman, 1987) From their loud sounds we can detect them easily by using automatic recorders Gibbon not call every day therefore, using autonomous recorders in the survey are widely used and can provide a highly efficient method of species monitoring Automated examination of acoustic recording with a field listening survey, using commercially available autonomous recorder provide a highly efficient method of species monitoring and custom call detection and classification software This method relies on loud sounds and is used by many researchers in their studies Currently, in Vietnam there are many national parks and nature reserves with highly diversed gibbon species Khe Nuoc Trong proposed nature reserve is one of the most important areas on the basis of biodiversity and conservation which consists of a 20,000-ha tract of Annamese Lowland Forest in Quang Binh Province, northcentral Vietnam It is a part of a larger (82,700 ha) tract that extends into the neighboring Quang Tri Province It is estimated that the protection of the forest at Khe Nuoc Trong will sequester approximately 50,000 tonnes of carbon dioxide (CO2) per year for the next 30 years (Viet nature, 2018) In Khe Nuoc Trong proposed nature reserve most of the species is endangered, due to degradation or loss of their habitats In the nature reserve many endangered and critically endangered species are present (Merriman et al.,unpulished) Khe Nuoc Trong proposed nature reserve is home to the Critically Endangered Sunda Pangolin (Manisjavanica) as well as three species of Endangered primates, the Red-shanked Douc (Pygathrixnemaeus), the Southern White-cheeked Gibbon (Nomascus siki) and the Haitinh Langur (Trachypithecus haitinhenis) (Viet nature, 2018) In Khe Nuoc Trong proposed nature reserve, there are many studies conducted on birds and the flora and fauna of the nature reserve such as (Tuong et al., 2018);(Viet nature, 2018);(Merriman et al., unpublished) etc and on southern white-cheeked gibbon rare studies are conducted in the proposed nature reserve Khe Nuoc Trong proposed nature reserve is facing many difficulties in monitoring its diversity because it covers a large area and contains a variety of high mountains Surveying of gibbon species by the traditional method may lead to a range of limitation and APPENDIX.2 Data of the recording posts of Khe Nuoc Trong proposed nature reserve with forest type, weather, slope and temperature NO Recorder Id Forest Type Installation Locus Slope Weather Temp Collection Weather Temp Date SM305135 TXB mount side 6-May-2017 69 gloomy 24 5/7/2017 sunny 27 SM305135 RTB mount side 7-May-2017 281 sunny 30 5/9/2017 sunny 28 No rain SM305188 TXB mount side 9-May-2017 259 rainy 28 5/7/2017 fog 24 no rain 28 5/7/2017 sunny 28 WN-N SM305188 RTB mount side 6-May-2017 (334) no rain SM305188 RTB mount side 7-May-2017 68 sunny 30 5/9/2017 Fog 23 SM305135 RTB mount side 9-May-2017 177 rainy 28 5/7/2017 sunny 28 SM30537 RTB mount side 6-May-2017 250 24 5/7/2017 sunny 26.5 SM30537 RTB mount side 7-May-2017 80 30 5/9/2017 gloomy 20.5 49 sunny NO Recorder Id SM30537 Forest Type RTB Installation Locus Slope Weather Temp Collection Weather Temp 90 tiny rain 29 5/7/2017 no rain 24.5 Date mount side 9-May-2017 No rain 10 SM304785 11 SM304785 12 SM304785 13 SM30537 rich forest mount side 6-May-2017 40 sunny 30 5/7/2017 Windy 25 mount side 7-May-2017 140 sunny 30 5/9/2017 rainy 21 RTB mount side 9-May-2017 252 rainy 28 5/7/2017 sunny 28.5 RTB mount side 2-May-2017 250 sunny 30 5/2/2017 sunny 27 TXN (near 14 SM305188 road) no rain, mount side 2-May-2017 57 windy gloomy, 29 5/2/2017 fog 23 windy, TXN (near mount side ( no rain, 15 SM305188 road ) HCM road) 2-May-2017 16 H4N TXB top, peak 3-May-2017 50 19 light windy 29 5/2/2017 sunny 24 sunny 24 5/3/2017 sunny 28 NO 17 Recorder Id M-305135 Forest Type TXB Installation Locus Slope Weather Temp Collection 45 sunny 29.5 5/4/2017 Weather Temp Date mount side 2-May-2017 25 windy , 18 SM304785 2-May-2017 330 sunny 29 5/2/2017 light 26 sunny 19 SM304785 RTB mount side 2-May-2017 79 sunny 29 5/4/2017 21 20 SM305135 RTB Top, Peck 28-Apr-2017 90 rainy 22.5 4/29/2017 21 21 SM305135 TXB mount side 29-Apr-2017 91 gloomy 26.5 5/1/2017 21 22 SM 304785 RTB mount side 28-Apr-2017 73 rainy 27 4/29/2017 21 23 SM 304785 RTB mount side 29-Apr-2017 175 sunny 29.5 5/1/2017 24 24 H4N TXB mount side 30-Apr-2017 170 no rain 27 4/30/2017 24 25 H4N TXB mount side 1-May-2017 170 windy, no 27 5/1/2017 25 51 NO Recorder Id Forest Type Installation Locus Slope Weather Temp Collection Weather Temp 22 4/29/2017 26 5/1/2017 sunny 27 22 4/29/2017 sunny 28 sunny 28 Date rain 26 SM305188 TXB mount side 28-Apr-2017 12 rainy, fog 24 shade, no 27 SM305188 TXB mount side 29-Apr-2017 159 rain, no sun 28 SM 30537 RTB top, peak 28-Apr-2017 fog, rainy East mount 29 SM 30537 RTB fog, side 29-Apr-2017 90 gloomy 23 5/1/2017 mount side 19-Apr-2017 60 sunny 26.5 4/21/2017 mount side 21-Apr-2017 123 27 4/23/2017 TXB soil 30 SM305135 mount 28 TXB soil 31 SM305135 mount 52 sunny 26 NO Recorder Id Forest Type Installation Locus Slope Weather Temp Collection Weather Temp Date rainy 32 SM305135 TXB mount side 23-Apr-2017 91 25.5 4/25/2017 Fog 23.5 no rain 33 SM305135 TXB mount side 14-Apr-2017 145 shady 23 4/15/2017 Windy 25 34 SM30537 TXB mount side 14-Apr-2017 145 rainy, fog 20 4/14/2017 27 35 SM305135 TXB mount side 17-Apr-2017 no rain 22.5 4/17/2017 21 36 SM305135 TXB mount side 17-Apr-2017 136 sunny 28 4/19/2017 24 37 SM305135 RTB mount side 21-Apr-2017 275 light sunny 26 4/23/2017 sunny 27 gloomy 23 4/25/2017 rainy 21 sunny 28 4/17/2017 East mountain fog, 38 SM 30537 RTB side 23-Apr-2017 39 SM 30537 RTB mount side 17-Apr-2017 53 270 23.5 NO 40 Recorder Id SM 30537 Forest Type RTB Installation Locus Slope Weather Temp Collection 270 light sunny 23 2/19/2017 220 light sunny 23 4/21/2017 Date mount side 17-Apr-2017 19/4/2017 41 SM 30537 RTB mount side (afternoon ) mount side 14-Apr-2017 tiny rain 21 4/14/2017 14-Apr-2017 tiny rain 21 4/14/2017 21 4/14/2017 fog 20 4/14/2017 near road 42 HN4 (TXB) 43 SM305188 near road fog, tiny 44 SM304785 near road mount side 14-Apr-2017 rain tiny rain, 45 SM305135 near road mount side 14-Apr-2017 46 H4N TXB mount road 18-Apr-2017 sunny 24 4/18/2017 47 H4N mount road 19-Apr-2017 sunny 25 4/18/2017 54 190 Weather Temp NO Recorder Id Forest Type Installation Locus Slope Weather Temp Collection 24 4/20/2017 Date windy, no 49 H4N TXG mount road 20-Apr-2017 50 SM30537 TXG mount road 14-Apr-2017 102 no rain 26 15/4/2077 51 SM305188 TXB mount road 17-Apr-2017 252 sunny 28 4/17/2017 52 H4N TXB mount road 17-Apr-2017 sunny 28 4/17/2017 53 SM305188 TXG mount road 17-Apr-2017 sunny 28 4/17/2017 54 SM305188 TXG mount road 19-Apr-2017 sunny 25 2/21/2017 55 SM305188 TXB mount road 21-Apr-2017 sunny 27 4/23/2017 Damp 25 4/25/2017 sunny, 26 4/21/2017 rain no rain 56 SM305188 TXB mount side 23-Apr-2017 57 H4N TXG mount side 21-Apr-2017 55 170 Weather Temp NO Recorder Id Forest Type Installation Locus Slope Weather Temp Collection 21 4/24/2017 Date windy 58 H4N 59 H4N 60 SM 304785 61 62 TXB mount side 24-Apr-2017 mount side 26-Apr-2017 rich forest mount side 19-Apr-2017 130 sunny 25 4/21/2017 SM 304785 RTB mount side 21-Apr-2017 130 sunny 27 4/23/2017 SM 304785 rich forest mount side 23-Apr-2017 40 sunny 25 4/25/2017 TXG= rich forest, TXB= Medium forest, 174 sunny, windy RTB= Medium forest 56 tiny rain 24 Weather Temp Appendix.3 Summary table of gibbon call detected in Khe Nuoc Trong proposed nature reserve from the recordings posts No of Gibbon call 10 11 12 13 14 Days of gibbon call heard Day1 Day Day3 1 0 1 1 1 1 1 1 1 1 0 1 1 1 1 Recorder date Compar tments Recorder Id Starting date Ending date 532 2-May-2017 2-May-2017 SM305188 515 17-Apr-2017 17-Apr-2017 SM305188 515 17-Apr-2017 17-Apr-2017 SM305188 516 19-Apr-2017 19-Apr-2017 SM30537 516 2-May-2017 2-May-2017 SM305188 515 2-May-2017 2-May-2017 SM304785 515 2-May-2017 2-May-2017 SM30537 516 16-Apr-2017 17-Apr-2017 SM304785 516 17-Apr-2017 18-Apr-2017 SM305135 517 28-Apr-2017 29-Apr-2017 SM304785 515 28-Apr-2017 29-Apr-2017 SM30537 534 28-Apr-2017 29-Apr-2017 SM30537 534 28-Apr-2017 29-Apr-2017 SM305135 535 6-May-2017 SM304785 57 7-May-2017 15 16 17 18 19 20 21 22 23 24 25 26 1 1 1 1 1 1 1 1 1 1 1 1 1 515 6-May-2017 7-May-2017 SM30537 517 6-May-2017 7-May-2017 SM304785 515 28-Apr-2017 29-Apr-2017 SM305135 534 17-Apr-2017 19-Apr-2017 SM305135 517 17-Apr-2017 19-Apr-2017 SM305135 517 19-Apr-2017 21-Apr-2017 SM305188 535 19-Apr-2017 21-Apr-2017 SM304785 534 19-Apr-2017 21-Apr-2017 SM305135 535 21-Apr-2017 23-Apr-2017 SM305188 535 21-Apr-2017 23-Apr-2017 SM30537 535 23-Apr-2017 25-Apr-2017 SM305135 535 29-Apr-2017 1-May-2017 SM305188 1: Gibbon detected on the day of the investigation 0: No gibbon detected on the day Blank: Recorder was not activate 58 Appendix.4 Summary of gibbon calls recorded during the survey Gibbons Calls Time of call Starting Ending Date of recordings Recording Id Compar tments 5h:17 5h:32 2-May-2017 2-May-2017 SM305188 532 5h:20 5h:40 17-Apr-2017 17-Apr-2017 SM305188 515 5h:35 5h:51 17-Apr-2017 17-Apr-2017 SM305188 515 5h:34 5h:55 19-Apr-2017 19-Apr-2017 SM30537 516 5h:32 5h:48 19-Apr-2017 19-Apr-2017 SM305188 516 5h:50 6h:07 16-Apr-2017 17-Apr-2017 SM304785 515 5h:33 5h:47 2-May-2017 2-May-2017 SM30537 515 16-Apr-2017 17-Apr-2017 SM304785 516 5h:57 5h:41 5h:40 5h:56 17-Apr-2017 18-Apr-2017 SM305135 516 10 5h:43 5h:57 28-Apr-2017 29-Apr-2017 SM304785 517 11 5h:16 28-Apr-2017 29-Apr-2017 SM30537 515 12 5h:19 5h:35 28-Apr-2017 29-Apr-2017 SM30537 534 13 5h:47 6h:04 28-Apr-2017 29-Apr-2017 SM305135 534 14 5h:20 5h:37 6-May-2017 7-May-2017 SM304785 535 15 5h:35 5h:44 6-May-2017 7-May-2017 SM30537 515 16 5h:41 5h:56 6-May-2017 7-May-2017 SM304785 517 17 5h:47 6h:07 28-Apr-2017 29-Apr-2017 SM305135 515 5h:27 59 Gibbons Calls Time of call Date of recordings Recording Id Compar tments 18 6h:05 6h:17 17-Apr-2017 19-Apr-2017 SM305135 19 5h:55 6h:07 17-Apr-2017 19-Apr-2017 SM305135 517 20 7h:13 7h:28 19-Apr-2017 21-Apr-2017 SM305188 517 21 5h:25 5h:39 19-Apr-2017 21-Apr-2017 SM304785 535 22 5h:37 5h:56 19-Apr-2017 21-Apr-2017 SM305135 534 23 5h:47 6h:03 21-Apr-2017 23-Apr-2017 SM305188 535 24 5h:35 5h:51 21-Apr-2017 23-Apr-2017 SM30537 535 25 6h:27 6h:39 23-Apr-2017 25-Apr-2017 SM305135 535 26 6h:17 7h:35 29-Apr-2017 1-May-2017 SM305188 535 60 534 Appendix.5 Sonogram of 20 different groups calls of southern white-cheeked gibbons from the recording of Khe Nuoc Trong Proposed nature reserve Sonogram.1 Two females and one male Sonogram.2 One male and one female Time:5h:46-6h:04 Time:5h:35-5h:51 Coordinates: 667747 -1881738 Coordinates: 670233-1878254 Sonogram.1 One females and one male Sonogram.2 One male and one female Time:6h:11-6h:28 Time:5h:41-5h:57 Coordinates: 666718-1881902 Coordinates: 667747 -1881738 Sonogram.1 One females and one male Sonogram.2 One male and one female Time:5h:46-6h:04 Time:5h:33-5h:51 Coordinates: 666527-1881227 Coordinates: 670049-187785 61 Sonogram.1 One females and one male Sonogram.2 One male and one female Time:5h:43-6h:03 Time:5h:18-5h:39 Coordinates: 670171-1877150 Coordinates: 666533-1881705 Sonogram.1 One females and one male Sonogram.2 One male and one female Time:5h:47-6h:07 Time:5h:50-6h:06 Coordinates: 670127-1877334 Coordinates: 665397-1881530 Sonogram.1 One females and one male Sonogram.2 One male and one female Time:5h:46-6h:05 Time:5h:37-5h:56 Coordinates: 669858-1877991 Coordinates: 666552-1880612 Sonogram.1 One females and one male Sonogram.2 Male, femaleand sub-adult Time:5h:37-5h:57 Time:6h:05-6h:19 Coordinates: 670233-1878254 Coordinates: 666552-1880612 62 Sonogram.1 One females and one male Sonogram.2 One male and one female Time:7:06-7h:13 Time:5h:41-5h:56 Coordinates: 666900-1880447 Coordinates: 669490-1877961 Sonogram.1 One females and one male Sonogram.2 One male and one female Time:5h:18-5h:35 Time:5h:33-5h:50 Coordinates: 666782-1880934 Coordinates: 669666-1877697 Sonogram.1 One females and one male Sonogram.2 One male and one female Time:6h:11-6h:25 Time:5h:56-6h:07 Coordinates: 670649-1878272 Coordinates: 666657-187975 63 ... lasts for 4-7 minutes In the days of the rain while analyzing data gibbon was detected in the rainy day In the days of the rain only days gibbon calls were detected and days of the rain no gibbon. .. with rainy Percentage of rain and no rainy days days and the days withoutrain (Figure 4.2) 80 70 60 50 40 30 20 10 Rain No rain Rainy and no rainy days of the survey in the April and May 2017... cheeked- gibbon (Nomascus siki) using autonomous recorders: A case study in the Khe Nuoc Trong proposed nature reserve? ??‟ 1.2 Goal To add information on the occurrence and distribution of southern white- cheeked