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Densities of Bornean orang-utans (Pongo pygmaeus morio) in heavily degraded forest and oil palm plantations in Sabah, Borneo

Seaman, David, Bernard, Henry, Ancrenaz, Marc, Coomes, David, Swinfield, Thomas, Milodowski, David, Humle, Tatyana, Struebig, Matthew J. (2019) Densities of Bornean orang-utans (Pongo pygmaeus morio) in heavily degraded forest and oil palm plantations in Sabah, Borneo. American Journal of Primatology, 81 (8). Article Number e23030. ISSN 1098-2345. (doi:10.1002/ajp.23030) (KAR id:74270)

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The conversion of forest to agriculture continues to contribute to the loss and fragmentation of remaining orang-utan habitat. There are still few published estimates of orang-utan densities in these heavily modified agricultural areas to inform range-wide population assessments and conservation strategies. In addition, little is known about what landscape features promote orang-utan habitat use. Using indirect nest count methods, we implemented surveys and estimated population densities of the Northeast Bornean orang-utan (Pongo pygmaeus morio) across continuous logged forest and forest remnants in a recently salvage-logged area and oil palm plantations in Sabah, Malaysian Borneo. We then assessed the influence of landscape features and forest structural metrics obtained from LiDAR data on estimates of orang-utan density. Recent salvage logging appeared to have little short-term effect on orang-utan density (2.35 ind/km2), which remained similar to recovering logged forest nearby (2.32 ind/km2). Orang-utans were also present in remnant forest patches in oil palm plantations, but at significantly lower numbers (0.82 ind/km2) than nearby logged forest and salvage-logged areas. Densities were strongly influenced by variation in canopy height but were not associated with other potential covariates. Our findings suggest that orang-utans currently exist, at least in the short-term, within human-modified landscapes, providing that remnant forest patches remain. We urge greater recognition of the role that these degraded habitats can have in supporting orang-utan populations, and that future range-wide analyses and conservation strategies better incorporate data from human-modified landscapes.

Item Type: Article
DOI/Identification number: 10.1002/ajp.23030
Uncontrolled keywords: habitat disturbance, human‐modified tropical landscape, LIDAR, oil palm, orang‐utan, Pongopygmaeus morio
Subjects: Q Science > QH Natural history > QH541 Ecology
Q Science > QH Natural history > QH75 Conservation (Biology)
Q Science > QL Zoology
Divisions: Divisions > Division of Human and Social Sciences > School of Anthropology and Conservation > DICE (Durrell Institute of Conservation and Ecology)
Funders: Natural Environment Research Council (
Depositing User: Matthew Struebig
Date Deposited: 23 Jun 2021 16:22 UTC
Last Modified: 31 Oct 2023 11:54 UTC
Resource URI: (The current URI for this page, for reference purposes)

University of Kent Author Information

Seaman, David.

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Humle, Tatyana.

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Struebig, Matthew J..

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