Effects of Shifting Cultivation on the Western Hoolock Gibbon (Hoolock hoolock) in Western Myanmar

Abstract

Shifting cultivation is a major driver of deforestation in tropical uplands. In western Myanmar, population growth has intensified the practice, shortening fallow periods and resulting in increased habitat degradation and fragmentation, which threaten wildlife survival. Arboreal species such as gibbons are particularly vulnerable due to their reliance on continuous canopy cover for survival. We investigated how shifting cultivation and associated human disturbances affect the density and abundance of the Western hoolock gibbon (Hoolock hoolock) in Man Wildlife Sanctuary, a newly established protected area, and its surrounding forest landscape in western Myanmar. Data were collected using point counts at 36 sampling grids covering 113 km² over 8 months (April–November 2023). Density estimates were derived from abundance using N-mixture models, and we examined the influence of landscape and human disturbance covariates on spatial variation in gibbon abundance across the study area. We estimated an average density of 1.6 groups/km². Of the seven landscapes and eight disturbance covariates tested, fire-related disturbances and proximity to human settlements—both closely associated with shifting cultivation—had the strongest negative influence on gibbon density. Our results suggest that Man Wildlife Sanctuary and its surrounding forests support a moderate density of Western hoolock gibbons compared with other regions in Myanmar. The lack of effective protection and management is a major problem, highlighting the need for targeted conservation measures and land-use planning to mitigate these threats.

Keywords

distance sampling / Man Wildlife Sanctuary / population estimate / slash-and-burn agriculture

References

[1] Akaike, H.1973. “Maximum Likelihood Identification of Gaussian Autoregressive Moving Average Models.” Biometrika 60, no. 2: 255–265. https://doi.org/10.1093/biomet/60.2.255.

[2] Arce-Peña, N. P., V. Arroyo-Rodríguez, P. A. D. Dias, I. Franch-Pardo, and E. Andresen. 2019. “Linking Changes in Landscape Structure to Population Changes of an Endangered Primate.” Landscape Ecology 34, no. 11: 2687–2701. https://doi.org/10.1007/s10980-019-00921-3.

[3] Arnold, T. W.2010. “Uninformative Parameters and Model Selection Using Akaike's Information Criterion.” Journal of Wildlife Management 74, no. 6: 1175–1178. https://doi.org/10.1111/j.1937-2817.2010.tb01236.x.

[4] Arroyo-Rodríguez, V., E. Cochoel-de la Mora, S. Mandujano, C. A. Chapman, R. Reyna-Hurtado, and L. Fahrig. 2013. “ Assessing Habitat Fragmentation Effects on Primates: The Importance of Evaluating Questions at the Correct Scale.” In Primates in Fragments: Complexity and Resilience, edited by L. K. Marsh and C. A. Chapman, 13–28. Springer.

[5] Arroyo-Rodríguez, V., and L. Fahrig. 2014. “Why Is a Landscape Perspective Important in Studies of Primates.” American Journal of Primatology 76, no. 10: 901–909. https://doi.org/10.1002/ajp.22271.

[6] Bartoń, K. (2024). MuMIn: Multi-Model Inference (R package version 1.48.4). https://CRAN.R-project.org/package=MuMIn.

[7] Borah, J. R., J. J. Gilroy, K. L. Evans, and D. P. Edwards. 2022. “The Value of Shifting Cultivation for Biodiversity in Northeast India.” Diversity and Distributions 28, no. 11: 1979–1992. https://doi.org/10.1111/ddi.13605.

[8] Brockelman, W. Y., and S. Srikosamatara. 1993. “Estimation of Density of Gibbon Groups by Use of Loud Songs.” American Journal of Primatology 29, no. 2: 93–108. https://doi.org/10.1002/ajp.1350290204.

[9] Buchhorn, M., B. Smets, L. Bertels, et al. (2020). Copernicus Global Land Service: Land Cover 100m: Collection 3: Epoch 2019: Globe [Data set]. Zenodo. https://doi.org/10.5281/zenodo.3518038.

[10] Burnham, K. P., and D. R. Anderson. 2002. Model Selection and Multimodel Inference: A Practical Information-Theoretic Approach ( 2nd ed. Springer.

[11] Chan, N., S. Takeda, R. Suzuki, and S. Yamamoto. 2016. “Assessment of Biomass Recovery and Soil Carbon Storage of Fallow Forests After Swidden Cultivation in the Bago Mountains, Myanmar.” New Forests 47, no. 4: 565–585. https://doi.org/10.1007/s11056-016-9531-y.

[12] Chandler, R. B., J. A. Royle, and D. I. King. 2011. “Inference About Density and Temporary Emigration in Unmarked Populations.” Ecology 92, no. 7: 1429–1435. https://doi.org/10.1890/10-2433.1.

[13] Cheyne, S. M., B. R. Capilla, A. K. , et al. 2019. “Home Range Variation and Site Fidelity of Bornean Southern Gibbons [Hylobates albibarbis] From 2010–2018.” PLoS One 14, no. 6: e0217784. https://doi.org/10.1371/journal.pone.0217784.

[14] Cheyne, S. M., C. J. H. Thompson, A. C. Phillips, R. M. C. Hill, and S. H. Limin. 2008. “Density and Population Estimate of Gibbons (Hylobates albibarbis) in the Sabangau Catchment, Central Kalimantan, Indonesia.” Primates 49, no. 1: 50–56. https://doi.org/10.1007/s10329-007-0063-0.

[15] Chivers, D. J. 2000. “ The Swinging Singing Apes: Fighting for Food and Family in Far-East Forests.” In The Apes: Challenges for the 21st Century, 1–28. Brookfield Zoo.

[16] Critical Ecosystem Partnership Fund. (2012). Indo-Burma Biodiversity Hotspot: 2012 Update. https://www.cepf.net/resources?search=indo-burma+2012+update.

[17] Dawrueng, T., D. Ngoprasert, G. A. Gale, S. Browne, and T. Savini. 2017. “Effect of Landscape Variables on the Long-Term Decline of Great Argus in the Rainforest of Southern Thailand.” Bird Conservation International 27, no. 2: 282–293. https://doi.org/10.1017/S0959270916000277.

[18] Deb, M., S. Choudhury, I. Sharma, et al. 2014. “Nutritional Stress in Western Hoolock Gibbon Due to Adverse Changes in Diet Pattern.” Journal of Microbiology, Biotechnology and Food Sciences 4, no. 2: 152–156. https://doi.org/10.15414/jmbfs.2014.4.2.152-156.

[19] Fan, P.-F., and H.-S. Ai. 2011. “Conservation Status of the Eastern Hoolock Gibbon (Hoolock leuconedys) in China.” Gibbon Journal 6: 22–25.

[20] Fiske, I., and R. Chandler. 2011. “Unmarked: An R Package for Fitting Hierarchical Models of Wildlife Occurrence and Abundance.” Journal of Statistical Software 43, no. 10: 1–23.

[21] Forest Department. (2015). National Biodiversity Strategy and Action Plan 2015–2020 (p. 137). Ministry of Environmental Conservation and Forestry, Myanmar.

[22] Funk, C., P. Peterson, M. Landsfeld, et al. 2015. “The Climate Hazards Infrared Precipitation With Stations—A New Environmental Record for Monitoring Extremes.” Scientific Data 2: 150066. https://doi.org/10.1038/sdata.2015.66.

[23] Geissmann, T. (2013). The Conservation Status of Hoolock Gibbons in Myanmar. Gibbon Conservation Alliance. https://www.gibbons.de/main/research/publications.html.

[24] Geist, H. J., and E. F. Lambin. 2002. “Proximate Causes and Underlying Driving Forces of Tropical Deforestation.” BioScience 52, no. 2: 143–150. https://doi.org/10.1641/0006-3568(2002)052[0143:PCAUDF]2.0.CO;2.

[25] Hartig, F. (2022). DHARMa: Residual Diagnostics for Hierarchical (Multi-Level/Mixed) Regression Models (R package version 0.4.6). R Foundation for Statistical Computing. https://florianhartig.github.io/DHARMa/.

[26] Hasan, S., H. Naher, T. Akhter, et al. 2025. “Impact of Seasonality on Food Selection and Home Range Size of the Western Hoolock Gibbon (Hoolock hoolock).” International Journal of Primatology 46, no. 1: 69–95.

[27] Htun, S., Z. H. Aung, W. Naing, et al. Forest Department, Nature and Wildlife Conservation Division, & Wildlife Conservation Society–Myanmar Program. (2006). Final Report on Conservation of the Hoolock Gibbon (Hylobates hoolock) in the Hukaung Tiger Reserve, North Myanmar: Population Surveys, Threat Assessment and Conservation Outreach, September 2006. Wildlife Conservation Society–Myanmar Program.

[28] Joseph, L. N., C. Elkin, T. G. Martin, and H. P. Possingham. 2009. “Modeling Abundance Using N-Mixture Models: The Importance of Considering Ecological Mechanisms.” Ecological Applications 19, no. 3: 631–642. https://doi.org/10.1890/07-2107.1.

[29] Kellner, K. F., A. D. Smith, J. A. Royle, M. Kéry, J. L. Belant, and R. B. Chandler. 2023. “The Unmarked R Package: Twelve Years of Advances in Occurrence and Abundance Modelling in Ecology.” Methods in Ecology and Evolution 14, no. 7: 1408–1415. https://doi.org/10.1111/2041-210X.14123.

[30] Kéry, M., and J. A. Royle. 2016. Applied Hierarchical Modeling in Ecology: Analysis of Distribution, Abundance and Species Richness in R and BUGS ( 1). Academic Press.

[31] Lawrence, D., C. Radel, K. Tully, B. Schmook, and L. Schneider. 2010. “Untangling a Decline in Tropical Forest Resilience: Constraints on the Sustainability of Shifting Cultivation Across the Globe.” Biotropica 42, no. 1: 21–30. https://doi.org/10.1111/j.1744-7429.2009.00599.x.

[32] Lwin, N., D. Ngoprasert, N. Sukumal, S. Browne, and T. Savini. 2022. “Status and Distribution of Hoolock Gibbon in the Newly Established Indawgyi Biosphere Reserve: Implication for Protected Area Management.” Global Ecology and Conservation 38: e02209. https://doi.org/10.1016/j.gecco.2022.e02209.

[33] Lwin, N., N. Sukumal, and T. Savini. 2021. “Modelling the Conservation Status of the Threatened Hoolock Gibbon (Genus Hoolock) Over Its Range.” Global Ecology and Conservation 29: e01726. https://doi.org/10.1016/j.gecco.2021.e01726.

[34] Marsh, L. K., C. A. Chapman, and V. Arroyo-Rodríguez. 2003. “ Primates in Fragments.” In Primates in Fragments: Ecology and Conservation, edited by L. K. Marsh, 6–7. Kluwer Academic/Plenum Publishers.

[35] Marshall, A. J., and M. Leighton. 2006. “ How Does Food Availability Limit the Population Density of White-Bearded Gibbons?” In Feeding Ecology in Apes and Other Primates, edited by G. Hohmann, M. Robbins, and C. Boesch, 48, 313–341. Cambridge University Press.

[36] Mazerolle, M. J. (2023). AICcmodavg: Model Selection and Multimodel Inference Based on (Q)AIC(c) (R Package Version 2.3-4). https://cran.r-project.org/package=AICcmodavg.

[37] Mukul, S. A., and J. Herbohn. 2016. “The Impacts of Shifting Cultivation on Secondary Forest Dynamics in Tropics: A Synthesis of the Key Findings and Spatio-Temporal Distribution of Research.” Environmental Science & Policy 55: 167–177. https://doi.org/10.1016/j.envsci.2015.10.005.

[38] Muzaffar, S. B., M. A. Islam, M. M. Feeroz, et al. 2007. “Habitat Characteristics of the Endangered Hoolock Gibbons of Bangladesh: The Role of Plant Species Richness.” Biotropica 39, no. 4: 539–545. https://doi.org/10.1111/j.1744-7429.2007.00298.x.

[39] Naher, H., H. Al-Razi, T. Ahmed, S. Hasan, A. Jaradat, and S. B. Muzaffar. 2021. “Estimated Density, Population Size and Distribution of the Endangered Western Hoolock Gibbon (Hoolock Hoolock) in Forest Remnants in Bangladesh.” Diversity 13, no. 10: 490. https://doi.org/10.3390/d13100490.

[40] Narayanaraj, G., and M. C. Wimberly. 2012. “Influences of Forest Roads on the Spatial Patterns of Human- and Lightning-Caused Wildfire Ignitions.” Applied Geography 32, no. 2: 878–888. https://doi.org/10.1016/j.apgeog.2011.09.004.

[41] Nath, T. K., M. Jashimuddin, M. Kamrul Hasan, M. Shahjahan, and J. Pretty. 2016. “The Sustainable Intensification of Agroforestry in Shifting Cultivation Areas of Bangladesh.” Agroforestry Systems 90, no. 3: 405–416. https://doi.org/10.1007/s10457-015-9863-1.

[42] O'Brien, T. G., M. F. Kinnaird, A. Nurcahyo, M. Prasetyaningrum, and M. Iqbal. 2003. “Fire, Demography and the Persistence of Siamang (Symphalangus syndactylus: Hylobatidae) in a Sumatran Rainforest.” Animal Conservation 6, no. 2: 115–121. https://doi.org/10.1017/S1367943003003159.

[43] Padalia, H., and P. P. Mondal. 2014. “Spatio-Temporal Trends of Fire in Slash and Burn Agriculture Landscape: A Case Study From Nagaland, India.” ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences II–8, no. 8: 53–59. https://doi.org/10.5194/isprsannals-II-8-53-2014.

[44] R Core Team. (2023). R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing. https://www.r-project.org/.

[45] Richards, S. A.2008. “Dealing With Overdispersed Count Data in Applied Ecology.” Journal of Applied Ecology 45, no. 1: 218–227. https://doi.org/10.1111/j.1365-2664.2007.01377.x.

[46] Royle, J. A.2004. “N-Mixture Models for Estimating Population Size From Spatially Replicated Counts.” Biometrics 60, no. 1: 108–115. https://doi.org/10.1111/j.0006-341x.2004.00142.x.

[47] Schmid, M., A. Heinimann, and J. G. Zaehringer. 2021. “Patterns of Land System Change in a Southeast Asian Biodiversity Hotspot.” Applied Geography 126: 102380. https://doi.org/10.1016/j.apgeog.2020.102380.

[48] Syxaiyakhamthor, K., D. Ngoprasert, N. Asensio, and T. Savini. 2020. “Identifying Priority Areas for the Conservation of the Critically Endangered Northern White-Cheeked Gibbon Nomascus leucogenys in Northern Lao.” Oryx 54, no. 5: 767–775. https://doi.org/10.1017/S0030605318001515.

[49] Thet, A. P. P., and N. Tokuchi. 2021. “The Influences of Traditional Shifting Cultivation on Soil Properties and Vegetation in the Bago Mountains, Myanmar.” Human Ecology 49, no. 5: 655–664. https://doi.org/10.1007/s10745-021-00255-8.

[50] Tolan, J., H.-I. Yang, B. Nosarzewski, et al. 2024. “Very High Resolution Canopy Height Maps From RGB Imagery Using Self-Supervised Vision Transformer and Convolutional Decoder Trained on Aerial LiDAR.” Remote Sensing of Environment 300: 113888. https://doi.org/10.1016/j.rse.2023.113888.

[51] Tran, D. V., A. Osawa, and T. T. Nguyen. 2011. “Recovery of Vegetation Structure and Species Diversity After Shifting Cultivation in Northwestern Vietnam, With Special Reference to Commercially Valuable Tree Species.” International Scholarly Research Notices 2011: 751472. https://doi.org/10.5402/2011/751472.

[52] Tun, W. K. K. N., N. Sukumal, D. Ngoprasert, N. M. Shwe, and T. Savini. 2023. “Gibbon Population Status and Long-Term Viability: Implication for a Newly Established Protected Area Management.” Global Ecology and Conservation 45: e02534. https://doi.org/10.1016/j.gecco.2023.e02534.

[53] Van Vliet, N., O. Mertz, A. Heinimann, et al. 2012. “Trends, Drivers and Impacts of Changes in Swidden Cultivation in Tropical Forest–Agriculture Frontiers: A Global Assessment.” Global Environmental Change 22, no. 2: 418–429. https://doi.org/10.1016/j.gloenvcha.2011.10.009.

[54] Wikramanayake, E., E. Dinerstein, C. J. Loucks, et al. 2002. Terrestrial Ecoregions of the Indo-Pacific: A Conservation Assessment. Island Press.

[55] Zuur, A. F., E. N. Ieno, and C. S. Elphick. 2010. “A Protocol for Data Exploration to Avoid Common Statistical Problems.” Methods in Ecology and Evolution 1: 3–14. https://doi.org/10.1111/J.2041-210x.2009.00001.X.

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2025 The Author(s). Integrative Conservation published by John Wiley & Sons Australia, Ltd on behalf of Xishuangbanna Tropical Botanical Garden (XTBG).