Orangutans display remarkable developmental changes and sexual differences in facial morphology, such as the flanges or cheek-pads that develop only on the face of dominant adult males. These changes suggest that facial morphology is an important factor in visual communication. However, developmental changes in facial morphology have not been examined in detail. We studied developmental changes in the facial morphology of the Borneo orangutan (Pongo pygmaeus) by observing 79 individuals of various ages living in the Sepilok Orangutan Rehabilitation Centre (SORC) in Malaysia and in Japanese zoos. We also analyzed photographs of one captive male that were taken over a period of more than 16 years. There were clear morphological changes that occurred with growth, and we identified previously unreported sexual and developmental differences in facial morphology. Light-colored skin around the eyes and mouth is most prominent in animals younger than 3 years, and rapidly decreases in area through the age of approximately 7 years. At the same time, the scattered, erect hairs on the head (infant hair) become thick, dense hairs lying on the head (adult hair) in both sexes. The results suggest that these features are infant signals, and that adult signals may include darkened face color, adult hair, whiskers, and a beard, which begin to develop after the age of approximately 7 years in both sexes. In females, the eyelids remain white even after 10 years, and turn black at around the age of 20; in males, the eyelids turn black before the age of 10. The whiskers and beards of adults are thicker in males than in females, and are fully developed before the age of 10 in males, while they begin to develop in females only after approximately 20 years. White eyelids and undeveloped whiskers and beards may be visual signals that are indicative of young adult females. Our results also show that the facial morphology of the unflanged male is similar to that of the adult female, although it has also been pointed out that unflanged males resemble younger individuals.
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 the 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 a little short-term effect on orang-utan density (2.35 ind/km 2 ), which remained similar to recovering logged forest nearby (2.32 ind/km 2 ). Orang-utans were also present in remnant forest patches in oil palm plantations, but at significantly lower numbers (0.82 ind/km 2 ) 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.
One Health is increasingly being used as a tool in ecosystem protection. The Orangutan Veterinary Advisory Group (OVAG) is working to address One Health concerns in Pongo spp. (orangutan) welfare and conservation. Orangutans are vital contributors to the ecosystem health of their range areas. Strengthening national capacity is crucial to make a lasting difference in the currently bleak outlook for orangutan species survival. OVAG is a capacity strengthening and expertise network that brings together all those working with orangutans, in- and ex-situ, to share knowledge, skills, and to collectively learn. Using the One Health paradigm embedded to enhance professional development, the OVAG network is successfully supporting conservation outcomes and impact. As part of our adaptive management approach, and to assess individual and organizational change attributable to the capacity strengthening work of OVAG, we evaluated technical skill test data, program satisfaction data, and asked participants to complete a self-reflective survey. This pilot study of our work demonstrates statistically significant improvements in conservation medicine (t = 5.481, p