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McGrath SJ, Liu J, Stevenson BC, Behie AM. Density and population size estimates of the endangered northern yellow-cheeked crested gibbon Nomascus annamensis in selectively logged Veun Sai-Siem Pang National Park in Cambodia using acoustic spatial capture-recapture methods. PLoS One 2023; 18:e0292386. [PMID: 38011169 PMCID: PMC10681233 DOI: 10.1371/journal.pone.0292386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 09/19/2023] [Indexed: 11/29/2023] Open
Abstract
Many gibbon species are threatened with extinction, including the endangered northern yellow-cheeked crested gibbon, Nomascus annamensis. Assessing gibbon populations and understanding how human disturbances and environmental factors impact these populations is vital for effective conservation planning. In 2010, auditory surveys revealed that Veun Sai-Siem Pang National Park (VSSP) in Cambodia contains one of the largest known N. annamensis populations in the world, with an estimated 456 (95% CI 421-490) gibbon groups. Illegal selective logging is common in the park, but the impact of continued logging on the gibbon population has not been investigated. To determine any change in the N. annamensis population since 2010, between January and April 2019 we conducted auditory surveys at 13 sites that were at least 4 km apart. We surveyed each site for three days, each day recording the gibbon calls heard over 3.25 hours from three listening posts located 500 m apart. At the same sites, we assessed the logging intensity using transects and ecological plots. Gibbon densities can be influenced by various environmental factors such as canopy height and forest type. Therefore, in addition to investigating the relationship between the density of N. annamensis groups and logging, we included five additional environmental variables in our acoustic spatial capture-recapture models. Our best fit model with the lowest AIC value included canopy height, forest type, distance to villages, and logging. We estimate that there are 389 (95% CI 284-542) N. annamensis groups currently in VSSP. Selective logging is widespread in the park, primarily targeting four tree species. The estimated felling time of these logged trees, together with previous reports, indicate that the species most targeted in VSSP varies over time. To conserve the N. annamensis population in VSSP, it is crucial that action is taken to reduce illegal logging.
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Affiliation(s)
- Sarah J. McGrath
- School of Archaeology and Anthropology, The Australian National University, Acton, ACT, Australia
| | - Jing Liu
- Department of Statistics, University of Auckland, Auckland, New Zealand
| | - Ben C. Stevenson
- Department of Statistics, University of Auckland, Auckland, New Zealand
| | - Alison M. Behie
- School of Archaeology and Anthropology, The Australian National University, Acton, ACT, Australia
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Vu TT, Doherty PF, T Nguyen H, Clink DJ, Nguyen MD, Dong HT, Cheyne SM, Giang TT, Phan DV, Ta NT, Tran DV. Passive acoustic monitoring using smartphones reveals an alarming gibbon decline in a protected area in the central Annamite Mountains, Vietnam. Am J Primatol 2023; 85:e23544. [PMID: 37572084 DOI: 10.1002/ajp.23544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 07/28/2023] [Accepted: 08/02/2023] [Indexed: 08/14/2023]
Abstract
Monitoring populations is critical for understanding how they respond to anthropogenic disturbance and for management of protected areas. The use of passive acoustic monitoring can improve monitoring efforts as it allows for collection of data on vocal animals at spatial and temporal scales that are difficult using only human observers. In this study, we used a multiseason occupancy model to monitor occurrence, apparent extinction, and colonization probabilities of a northern yellow-cheeked gibbon, Nomascus annamensis population with acoustic data collected from mobile smartphones in Dakrong Nature Reserve, Vietnam. Forty-five sites were randomly selected for repeated surveys in 2019 and 2022. At each site, a mobile smartphone was attached to a tree and recorded sounds for 4.2 days and 3.89 days on average, in 2019 and 2022, respectively. We manually annotated spectrograms for the presence of gibbon calls, and we detected gibbons at 24 and 12 recording posts in 2019 and 2022, respectively. Estimated local apparent extinction from occupancy models was high with 67% of occupied sites in 2019 becoming unoccupied in 2022. Apparent colonization was low with ~25% of unoccupied sites in 2019 becoming occupied in 2022. As a result, the apparent occurrence probability declined from 0.58 in 2019 to 0.30 in 2022. If the absence of calls indicates that cells are unoccupied this would mean an alarming decline of the gibbon population in the nature reserve. We suggest that in the areas with high hunting pressure, monitoring intervals should be shortened to at least yearly. In addition, urgent actions, such as patrolling, or gun confiscation, should be implemented to conserve the gibbon populations in Dakrong Nature Reserve and other protected areas with the same management context.
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Affiliation(s)
- Thinh T Vu
- Department of Wildlife, Faculty of Forest Resource and Environment Management, Vietnam National University of Forestry, Hanoi, Vietnam
| | - Paul F Doherty
- Department of Fish, Wildlife, and Conservation Biology, Warner College of Natural Resources, Colorado State University, Fort Collins, Colorado, USA
| | - Hoa T Nguyen
- Institute for Tropical biodiversity and Forestry, Hanoi, Vietnam
| | - Dena J Clink
- Cornell Lab of Ornithology, K. Lisa Yang Center for Conservation Bioacoustics, Cornell University, Ithaca, New York, USA
| | - Manh D Nguyen
- Department of Wildlife, Faculty of Forest Resource and Environment Management, Vietnam National University of Forestry, Hanoi, Vietnam
| | - Hai T Dong
- Department of Wildlife, Faculty of Forest Resource and Environment Management, Vietnam National University of Forestry, Hanoi, Vietnam
| | - Susan M Cheyne
- Faculty of Humanities and Social Sciences, Oxford Brookes University, Headington Campus, Oxford, UK
| | - Toan T Giang
- Department of Wildlife, Faculty of Forest Resource and Environment Management, Vietnam National University of Forestry, Hanoi, Vietnam
| | - Dai V Phan
- Department of Wildlife, Faculty of Forest Resource and Environment Management, Vietnam National University of Forestry, Hanoi, Vietnam
| | - Nga T Ta
- Department of Wildlife, Faculty of Forest Resource and Environment Management, Vietnam National University of Forestry, Hanoi, Vietnam
| | - Dung V Tran
- Department of Wildlife, Faculty of Forest Resource and Environment Management, Vietnam National University of Forestry, Hanoi, Vietnam
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Widyastuti S, Perwitasari-Farajallah D, Iskandar E, Prasetyo LB, Setiawan A, Aoliya N, Cheyne SM. Population of the Javan Gibbon ( Hylobatesmoloch) in the Dieng Mountains, Indonesia: An updated estimation from a new approach. Biodivers Data J 2023; 11:e100805. [PMID: 37448691 PMCID: PMC10336555 DOI: 10.3897/bdj.11.e100805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 06/20/2023] [Indexed: 07/15/2023] Open
Abstract
The Javan gibbon (Hylobatesmoloch) is endemic to the island of Java and its distribution is restricted from the western tip of Java to the Dieng Mountains in Central Java. Unlike the other known habitats that hold a large population of Javan gibbons, the Dieng Mountains have not been protected and experience various threats. This study, which was conducted in 2018 and 2021, aimed to provide an update of the current density and population size of Javan gibbons in Dieng after the most recent study in 2010 and to investigate their relationships with habitat characteristics (vegetation and elevation). The triangulation method and a new acoustic spatial capture-recapture method were used to estimate group density. A new approach for extrapolation, based on the habitat suitability model, was also developed to calculate population size. The results show that the Javan gibbon population in the Dieng Mountains has most likely increased. The mean group density in each habitat type was high: 2.15 groups/km2 in the low suitable habitat and 5.55 groups/km2 in the high suitable habitat. The mean group size (3.95 groups/km2, n = 20) was higher than those reported in previous studies. The overall population size was estimated to be 1092 gibbons. This population increase might indicate the success of conservation efforts during the last decade. However, more effort should be made to ensure the long-term future of this threatened species. Although the density significantly differed between habitat suitability types, it was not influenced by the vegetation structure or elevation. A combination of multiple variables will probably have a greater effect on density variation.
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Affiliation(s)
- Salmah Widyastuti
- Animal Biosciences Program, Department of Biology, Faculty of Mathematics and Natural Sciences, IPB University, Bogor, IndonesiaAnimal Biosciences Program, Department of Biology, Faculty of Mathematics and Natural Sciences, IPB UniversityBogorIndonesia
| | - Dyah Perwitasari-Farajallah
- Department of Biology, Faculty of Mathematics and Natural Sciences, IPB University, Bogor, IndonesiaDepartment of Biology, Faculty of Mathematics and Natural Sciences, IPB UniversityBogorIndonesia
- Primate Research Centre, IPB University, Bogor, IndonesiaPrimate Research Centre, IPB UniversityBogorIndonesia
| | - Entang Iskandar
- Primate Research Centre, IPB University, Bogor, IndonesiaPrimate Research Centre, IPB UniversityBogorIndonesia
| | - Lilik B Prasetyo
- Department of Forest Resources Conservation and Ecotourism, Faculty of Forestry and Environment, IPB University, Bogor, IndonesiaDepartment of Forest Resources Conservation and Ecotourism, Faculty of Forestry and Environment, IPB UniversityBogorIndonesia
| | - Arif Setiawan
- SwaraOwa, Yogyakarta, IndonesiaSwaraOwaYogyakartaIndonesia
| | - Nur Aoliya
- Animal Biosciences Program, Department of Biology, Faculty of Mathematics and Natural Sciences, IPB University, Bogor, IndonesiaAnimal Biosciences Program, Department of Biology, Faculty of Mathematics and Natural Sciences, IPB UniversityBogorIndonesia
| | - Susan M Cheyne
- Faculty of Humanities, Social Sciences and Law, Oxford Brookes University, Oxford, United KingdomFaculty of Humanities, Social Sciences and Law, Oxford Brookes UniversityOxfordUnited Kingdom
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Yang JH, Huang XY, Jin SH, Chan BPL. Filling a longstanding knowledge gap: Population size and conservation status of the Endangered Gaoligong hoolock Gibbon (Hoolock tianxing) in Houqiao Town, Yunnan. Glob Ecol Conserv 2020. [DOI: 10.1016/j.gecco.2020.e01347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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