<![CDATA[ABSTRACT. Leaves are the primary feeding source of proboscis monkey (Nasalis larvatus), Borneo endemic primates and protected by Indonesian law. The objective of the study was to inventory the plant species of feed sources and to determine the part of the plant that became the main feed for bekantan in the swamp forest. The number of species occurrences and parts of plants eaten by proboscis was calculated by the IARF method. The density of feeding source plant (pole level) was calculated in 5 (10 m x 10 m) plot and the sapling level in 5 (5 m x 5 m) subplots. The selection ratio of IARF/K and its relative selection ratio was determined. The feeding source plants were galam (Melaleuca leucadendron), mangium (Acacia mangium), and karamunting (Melastoma affine). The leaves were part of the plant that was the main source of feed. Karamunting was a plant that has the greatest selection ratio in the bekantan diet. Keywords: proboscis monkey; leaves; diet; swamp forestABSTRAK.Daun adalah sumber pakan utama bekantan (Nasalis larvatus), primata endemik Borneo dan dilindungi peraturan perundang-undangan Indonesia.Tujuan penelitian adalah menginventarisasi spesies tumbuhan sumber pakan dan menentukan bagian tumbuhan yang menjadi pakan utama bagi bekantan di hutan rawa. Jumlah kejadian spesies dan bagian tumbuhan tersebut dimakan oleh bekantan dihitung dengan metode IARF. Kerapatan tumbuhan pakan tingkat tiang dihitung dalam 5 plot yang luas setiap plotnya (10 x 10) m2 dan tingkat pancang dalam 5 subplot yang luas setiap subplotnya (5 x 5) m2. Rasio seleksi IARF/K serta rasio seleksi relatifnya ditentukan. Bekantan memakan galam (Melaleuca leucadendron), mangium (Acacia mangium), dan karamunting (Melastoma affine). Daun adalah bagian tumbuhan yang menjadi sumber pakan utama. Karamunting merupakan tumbuhan yang rasio seleksinya terbesar dalam pakan bekantan.Kata kunci:bekantan; daun; pakan; hutan rawa]]>
