Decomposition dynamics of an orangutan (Pongo pygmaeus morio) carcass in a tropical forest: implications for conservation practices
Author(s)
Heon, Sui P
Bernard, Henry
Ewers, Robert M
Type
Journal Article
Abstract
Over the past decade, more than 600 rehabilitated Bornean Orangutans (Pongo pygmaeus morio) have been released into protected forests in Borneo. Releasing rehabilitant Bornean Orangutans into the wild is a standard conservation practice, yet monitoring postrelease survival remains a challenge. Limited data exist on post release survival, with many individuals classified as “missing but presumed dead” due to the absence of a carcass for confirmation. Detecting carcasses in tropical forests is particularly difficult due to dense vegetation and the narrow time frame for observing remains before complete decomposition or scavenger removal. Here, we report the first documented observation of a wild adult female Bornean Orangutan carcass decomposing process in the Danum Valley Conservation Area, Malaysian Borneo, on 21 May 2023. The approximately 30 kg carcass was monitored using camera traps and field observations. Decomposition was assessed using Payne's (1965) decomposition framework, the Total Body Score (TBS) system, and Accumulated Degree Days (ADD) to evaluate the influence of ambient temperature on decay. Decomposition progressed to the dry-remains stage within 6 days, primarily driven by vertebrate scavengers such as the Asian water monitor lizard (Varanus salvator) and blow flies (Calliphoridae). This rapid decomposition rate challenges existing knowledge on the rate of decomposition of medium-sized carcasses (> 10 kg) and suggests that the common practice of weekly monitoring for post-release orangutans may be insufficient. Understanding decomposition processes and scavenger activity in tropical forests can improve carcass detection, refine mortality estimates for released Orangutans and other endangered species, and enhance conservation strategies for this critically endangered primate.
Date Issued
2025-12-01
Date Acceptance
2025-12-01
Citation
Ecology and Evolution, 2025, 15 (12)
ISSN
2045-7758
Publisher
Wiley
Journal / Book Title
Ecology and Evolution
Volume
15
Issue
12
Copyright Statement
© 2025 The Author(s). Ecology and Evolution published by British Ecological Society and John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Publication Status
Published
Article Number
e72662
Date Publish Online
2025-12-11