Abundance, feeding and behavioural ecology of Orangutans (Pongo pygmaeus morio) in the fragmented forests of the Kinabatangan floodplain

• Main Author: Felicity Anne Louise Oram
• Format: Thesis
• Language: English; English
• Published: 2018
• Subjects: QL750-795 Animal behavior
• Online Access: https://eprints.ums.edu.my/id/eprint/33510/1/Abundance%2C%20Feeding%20And%20Behavioural%20Ecology%20Of%20Orangutans%20%28Pongo%20Pygmaeusmoriojin%20The%20Fragmented%20Forests%20Of%20The%20Kinabatangan%20Floodplain.24PAGES.pdf; https://eprints.ums.edu.my/id/eprint/33510/2/Abundance%2C%20Feeding%20And%20Behavioural%20Ecology%20Of%20Orangutans%20%28Pongo%20Pygmaeusmoriojin%20The%20Fragmented%20Forests%20Of%20The%20Kinabatangan%20Floodplain.FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/33510/

This study characterized core life history determinants, feeding ecology, local abundance variation and population trends of orangutans, Pongo pygrnaeus mario, in the degraded floodplain of the Lower Kinabatangan River. This is the first long-term comprehensive analysis of wild orangutan survival in a landscape that has been highly disturbed from commercial timber extraction, and greatly fragmented by extensive nearby land conversion. The study also proposed key aspects necessary for orangutan conservation in this region. A novel measure of habituation was established based on feeding-to-resting ratios to build a dataset representative of all age-sex classes, including both more resident animals and transient visitors to the study site. Floristically, the Kinabatangan now has higher baseline fruit abundance with lower synchronous peaks and less extreme seasonality, in sharp contrast to intact primary forest at Danum Valley. Over 50% less cambium feeding activity was observed compared to Danum Valley. Therefore, orangutans in this degraded forest experience less fruit shortfall and less reliance on fall-back foods. This is indicative that sufficient habitat heterogeneity and plant diversity has been retained in this degraded floodplain region to support this large-bodied primate. Also, no correlation between feeding time on fall-back foods (leaves, cambium) and increased daytime rest was found, signifying additional rest for digestive processing of fibrous foods was not required. Mean travel time was significantly shorter than Danum Valley, although mean daily travel distance was not different. This suggests orangutans make use of the extensive vine profusion in this degraded habitat to move laterally with greater efficiency and speed than conspecifics in primary forests. A positive correlation between general forest productivity (shoot production) and unripe fruit production with orangutan abundance and a negative correlation with ripe fruit and orangutan abundance was found. Since studies have shown larger patch size (fruit per unit area) is a key predictor of orangutan movement, more transient individuals (males) likely move away at peak ripeness when resident orangutans and other more selective frugivores begin to also deplete the resource. Overall, localised population trends were stable from 2005-2016 but short-term variation, characteristic of primary floodplains, was still observed. Mean daily travel distances varied in adult male polymorphs (flanged, unflanged) and in females by reproductive status and offspring age, suggesting a possible social constraint to movement that could confound conservation efforts. Therefore, ongoing monitoring is necessary to assure continued access across human transformed landscapes is maintained. Also, further study is warranted of the role female hierarchy and adult male polymorphs play in territorial defence, resource guarding and reproduction that could potentially limit long-term viability in this now highly fragmented mixed-use landscape. These findings also highlight the importance of scientifically rigorous behavioural study if we are to have the proper tools to manage orangutans in an anthropogenic environment.