Locomotor behavior of wild orangutans (pongo pygmaeus wurmbii) in disturbed peat swamp forest, Sabangau, Central Kalimantan, Indonesia

Abstract

This study examined the locomotor behavior of wild Bornean orangutans (P. p. wurmbii) in an area of disturbed peat swamp forest (Sabangau Catchment, Indonesia) in relation to the height in the canopy, age-sex class, behavior (feeding or traveling), and the number of supports used to bear body mass. Backward elimination log-linear modeling was employed to expose the main influences on orangutan locomotion. Our results showed that the most important distinctions with regard to locomotion were between suspensory and compressive, or, orthograde (vertical trunk) and pronograde (horizontal trunk) behavior. Whether orangutans were traveling or feeding had the most important influence on locomotion whereby compressive locomotion had a strong association with feeding, suspensory locomotion had a strong association with travel in the peripheral strata using multiple supports, whereas vertical climb/descent and oscillation showed a strong association with travel on single supports in the core stratum. In contrast to theoretical predictions on positional behavior and body size, age-sex category had a limited influence on locomotion. The study revealed that torso orthograde suspension dominates orangutan locomotion, concurring with previous studies in dipterocarp forest. But, orangutans in the Sabangau exhibited substantially higher frequencies of oscillatory locomotion than observed at other sites, suggesting this behavior confers particular benefits for traversing the highly compliant arboreal environment typical of disturbed peat swamp forest. In addition, torso pronograde suspensory locomotion was observed at much lower levels than in the Sumatran species. Together these results highlight the necessity for further examination of differences between species, which control for habitat.

Fine-Scale Habitat Use by Orang-Utans in a Disturbed Peat Swamp Forest, Central Kalimantan, and Implications for Conservation Management

“…[2006] found that the nutritional value of the red-tailed monkey's (Cercopithecus ascanius) diet was significantly reduced in heavily logged forest, emphasising the implications that logging can have on animal health [Gillespie et al ., 2005]. When a forest is logged, the removal of large trees disrupts the upper canopy affecting travel routes and forcing arboreal species to descend to lower levels or even travel on the ground [Johns, 1986;Manduell et al, 2011]. This in turn can increase predation risks from terrestrial predators.…”

Orangutan Energetics and the Influence of Fruit Availability in the Nonmasting Peat-swamp Forest of Sabangau, Indonesian Borneo

“…This runs counter to expectations of increased energy expended on travel being a potential cause of negative energy balance and possibly represents a statistical anomaly due to the relatively small sample size, with the accompanying interpretation that day range has no true influence on ketone production in flanged males in Sabangau. The absence of expected relationships here may also be related to potentially more energy efficient travel in the relatively continuous lower canopies of Sabangau, where the incidence of tree sway, identified as a highly energy efficient form of locomotion (Thorpe et al 2007), is much higher than in other habitat types studied to date (Manduell 2008). …”

Comparing spatial capture–recapture modeling and nest count methods to estimate orangutan densities in the Wehea Forest, East Kalimantan, Indonesia

“…Recent studies demonstrate that it is possible to obtain captures of primates with arboreal camera traps (Gregory et al, 2014) and cameras placed in carefully selected arboreal locations could supplement records on the ground. This might be especially useful in areas where there is a sex difference in use of the ground, as may be the case at certain locations in Wehea (e.g., sepans) and has been found at other orangutan study sites (e.g., Manduell et al, 2011). This technique, however, presents many hurdles (e.g., determining placement of cameras, the requirement of specialized expertise and equipment) and may also not be cost-effective in many areas.…”