RESUMO
The Cao Vit gibbon (Nomascus nasutus) has only one population with about 110 individuals living in a degraded karst forest along the China-Vietnam border. Investigation of food choice in relation to chemical nutrition will offer important insights into its conservation. We studied the food choice of two groups of Cao Vit gibbons using instantaneous scan sampling in Bangliang National Nature Reserve, Guangxi, China, over 4 years, and analyzed the chemical components (total nitrogen, TN; water-soluble sugar, WSS; crude fat, CF; neutral detergent fiber, NDF; acid detergent fiber, ADF; acid detergent lignin, ADL; condensed tannin, CT; and ash) of 48 food plant parts and 22 non-food plant parts. Fruits and figs that are rich in sugar are important food resources for gibbons. For other food types, flowers are a good source of total nitrogen and carbohydrates, and leaves and buds provide sources of protein and minerals. Cao Vit gibbons selected fruits that contain less total nitrogen, less acid detergent fiber and more water-soluble sugar than non-food fruits. Several food species that were heavily consumed by Cao Vit gibbons are suggested as potential tree species for ongoing habitat restoration.