Locomotion behavior of cao vit gibbon (Nomascus nasutus) living in karst forest in Bangliang Nature Reserve, Guangxi, China.

The cao vit gibbon is a critically endangered species. Only approximately 110 individuals remain in degraded karst forest along the China-Vietnam border. Karst forest is unusual gibbon habitat. Currently, the canopy height of cao vit gibbon habitat is approximately 10 m. Research on the locomotor behavior of gibbons living in this particular forest type might provide important insight into locomotor stability and variability of gibbons. We used 5 min scan samples to record the locomotion mode, support use and canopy strata of gibbons in 3 groups for 2096 h between January 2008 and December 2009. Although cao vit gibbon habitat has a lower canopy in comparison to that of other forests inhabited by gibbons, cao vit gibbons displayed a similar overall locomotor pattern to other gibbon species (Symphalangus syndactylus, Hylobates lar and Hylobates agilis) in which brachiation dominate their locomotor behavior. Cao vit gibbons spent most of their time travelling on inclined branches (2-10 cm) in the middle stratum through the forest canopy. Adult females appear to more often employ safer modes of locomotion (bridging more often and brachiation less), while adult males choose riskier modes (leaping more and climbing less). As gibbons increased in body weight, as they grew from infant to adult, they tended to use larger supports. This research documented that locomotor behavior in Hylobatidae is strongly determined by anatomical characters, but cao vit gibbons also show the ability to use various supports, enabling them to survive in karst forest.