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Population dynamics of the proboscis monkey Nasalis larvatus in the Lower Kinabatangan, Sabah, Borneo, Malaysia

  • Ikki Matsuda (a1), Nicola K. Abram (a2), Danica J. Stark (a3), John C. M. Sha (a4), Marc Ancrenaz (a5), Benoit Goossens (a3), Isabelle Lackman (a5), Augustine Tuuga (a6) and Takuya Kubo (a7)...


The Endangered proboscis monkey Nasalis larvatus is endemic to the island of Borneo. Habitat loss is a major threat to this species, and an understanding of long-term demographic trends is crucial for its conservation. We assessed the population trends and group sizes of proboscis monkeys over 10 years in the Lower Kinabatangan floodplain in Sabah, Malaysian Borneo. Comparisons of observed populations between 2004 and 2014 revealed significantly reduced group sizes, which is probably a result of forest fragmentation. Three long-term studies over 34–73 months in specific areas showed fluctuating estimated densities in each area, but no overall population increase or decrease. Riparian forests are the most important habitat for these monkeys, and one reason for the relatively stable population could be that there were only minor losses of forest along rivers during 2004–2014 because protected areas have been established in the region in 2005. However, proboscis monkey habitat remains under threat in areas allocated for oil palm, and protection of these areas is paramount to maintaining this population.


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Contributed equally to this work

Also at: Wildlife Research Center, Kyoto University, Kyoto, Japan; Japan Monkey Centre, Inuyama, Japan; Institute for Tropical Biology and Conservation, Universiti Malaysia Sabah, Kota Kinabalu, Malaysia

Also at: Waikiki Condominium, Jalan Aru, Tanjung Aru, 88100, Kota Kinabalu, Sabah, Malaysia; The University of Queensland, School of Biological Sciences, Brisbane, Australia; ARC Centre of Excellence for Environmental Decisions, The University of Queensland, Brisbane, Australia


Also at: Sabah Wildlife Department, Kota Kinabalu, Malaysia

Supplementary material for this article is available at



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Population dynamics of the proboscis monkey Nasalis larvatus in the Lower Kinabatangan, Sabah, Borneo, Malaysia

  • Ikki Matsuda (a1), Nicola K. Abram (a2), Danica J. Stark (a3), John C. M. Sha (a4), Marc Ancrenaz (a5), Benoit Goossens (a3), Isabelle Lackman (a5), Augustine Tuuga (a6) and Takuya Kubo (a7)...


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