Orangutan density 765


TABLE 1 Effective strip width (± SE), Akaike’s information criterion (AIC),%coefficient of variation (CV), mean density of orangutan nests (± SE, with 95% CI) and estimate of mean individual density (with 95% CI) in peat swamp forests of Sungai Palin surveyed in 2017, and Nanga Awen surveyed in 1991.


Location Sungai Palin


Effective strip width ± SE (km) AIC % CV 0.011 ± 0.0014


Nanga Awen 0.013 ± 0.0027


470.34 37.01 446.26 36.12


Mean density (per km2) Nests ± SE (95% CI)


222 ± 82.14 (88.32–557.84) 449 ± 162.43 (175.11–1,154.60)


Individuals (95% CI) 1.29 (0.51–3.25)


2.62 (1.02–6.72)


TABLE 2 Summary of information available on the density of the three Bornean orangutan subspecies, based on nest count surveys. Location


Subspecies


Sangkulirang peninsula Nanga Awen


Danau Sentarum National Park Betung Kerihun National Park Sungai Palin


Sebangau National Park Mega-Rice project


P. pygmaeus morio


P. pygmaeus pygmaeus P. pygmaeus pygmaeus P. pygmaeus pygmaeus P. pygmaeus pygmaeus P. pygmaeus wurmbii P. pygmaeus wurmbii


Survey year Density (per km2) Source 2003 0.82–5.25


1991 2.62


1996 3.29–4.09 2005 0.20–1.01 2017


1.29


1995–1996 0.44–1.72 2009 1.62–4.63


local communities of the importance of the orangutan popu- lation outside these protected areas is essential to help main- tain connectivity between the orangutan populations. Our surveys and calculations of orangutan density form


a baseline for monitoring this orangutan population and for informing conservation action and management of non-timber forest products in the watershed landscapes of Sungai Palin. The orangutan population in the land- scape of Sungai Palin, Nanga Awen and surrounding areas shold be a priority for community-based conservation.


Acknowledgements We thank LTS International for giving AY the opportunity to survey orangutans in Sungai Palin peat land forest while he conducted a biodiversity survey in Nanga Lauk Village Forest for the ADB-funded project Sustainable Forest and Biodiversity Management in Borneo, Fauna & Flora International, UK, for the data from the 1991 surveys in Nanga Awen, the Nanga Lauk community, especially Simon, Hamdi and Yosep who helped us in Sungai Palin, and Chaerul Saleh and I Made Wedana, the orangutan survey team in Nanga Awen.


Author contributions Study design and field work: AY; data analysis: AY; writing: all authors.


Conflicts of interest None.


Ethical standards This research did not involve human subjects, experimentation with animals or collection of specimens, and abided by the Oryx guidelines on ethical standards.


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Oryx, 2020, 54(6), 763–766 © 2019 Fauna & Flora International doi:10.1017/S0030605319000875


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