Use of the Forest Canopy by the Agile Gibbon

Abstract

Brachiation was the main form of locomotion and took place along branches and boughs in the upper canopy. The posture during feeding depended on the substrate, with the gibbons sitting on branches but hanging in twigs. During foraging the gibbons hung more, even on branches, but as only short stops were made this is probably to increase mobility. Feeding on fruit took place mainly in the middle canopy on small trees; feeding on leaves and foraging occurred evenly throughout the middle and upper canopies. Gibbons are light mobile animals with a rapid and direct form of locomotion that enables them to exploit dispersed food sources and to defend a large territory.

Biomechanics of phalangeal curvature

“…Lesser apes were selected for their specialized suspensory behavior (Fleagle, 1974;Gittens, 1983), markedly curved phalanges, and availability for study. The third proximal phalanx was chosen because its central position in the hand ensures a weight-bearing role and buffers it from mediolateral forces (not modeled here).…”

“…Although it would be very interesting to sample a range of support sizes, orientations, and material properties (e.g., support flexibility), examining the influence of support variation is beyond the scope of this study. The support size (3.8 cm diameter) employed here falls within the 2 to 10 cm range of branch diameters reported to be most commonly used by gibbons while brachiating in their natural habitats (Gittens, 1983), and was the same support size used in the EMG experiments documenting muscle recruitment. Figure 1 illustrates the representative hand posture sampled here.…”

The effect of substrate compliance on the biomechanics of gibbon leaps

“…'Branch pumping', observed in wild siamangs (Fleagle, 1976) before a leap may be a mechanism to utilise the energy stored in the branch for propulsion. However, most gap-crossing leaps are conducted from fine terminal branches (Fleagle, 1976;Gittins, 1983;Crompton et al, 1993;Sati and Alfred, 2002), with low resonant frequencies (McMahon and Kronauer, 1976) making efficient energy storage and recovery during leaping from terminal branches unlikely (Alexander, 1991). Indeed, wild sifaka were shown to take-off at the 'wrong' time for efficient energy return from thin branches (Demes et al, 1995).…”

“…Although renowned as specialist brachiators (Fleagle, 1974;Bertram et al, 1999), recent studies have highlighted that gibbons possess anatomical adaptations to execute hindlimb-powered movements such as leaping Channon et al, 2010a). Gibbons commonly utilise leaping for 20-25% of their locomotor activity (Fleagle, 1976;Gittins, 1983;Sati and Alfred, 2002) and regularly leap from thin terminal branches during travel and feeding (Kappeler, 1984;Sati and Alfred, 2002). Channon et al (Channon et al, 2010b) demonstrated that leaping is a highly versatile locomotor mode for gibbons, which probably use one of a number of leap types depending on the environment and leap function (i.e.…”

The extraordinary athletic performance of leaping gibbons

“…Indeed, gibbon skeletons recovered from the forest floor display open fractures and other impact-related pathologies [12]. Therefore, the selective advantage of successful leaps is undoubtedly high [11,13].…”