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Vietnamese Journal of Primatology


The Tonkin sub-nosed (TSN) monkey (Rhinopithecus avunculus)is both critically endangered and endemic to northeastern Vietnam. This species is one of the world’s top 25 endangered primates. Rhinopithecus avunculusis known only from three isolated populations that are located in Ha Giang, Tuyen Quang and Bac Kan Provinces. The remaining population is estimated to consist of approximately 150 individuals. The two largest populations are found in Na Hang Nature Reserve (Tuyen Quang Province) and Khau Ca area (Ha Giang Province).

The diet of the TSN monkeys consists of a broad range of plants and plant parts. Since 2004, 31 food species have been identified belonging to 21 families. Leaf stems and fruits are the most common part of the TSN monkeys’ diet (27.78%), followed by young leaves (flush leaves) (11.11%), unripe fruit (22.22%), inflorescences and flowers (8.33%) and seeds (2.78%). The plant foods most frequently consumed by the TSN monkeys are Iodes seguini(leaf stems and ripe fruits), Garcinia fagraeoides(leaf stems), Acer tonkinensis(leaf stems), Excentrodendron tonkinensis(flowers), and Brassaiopsis stellata. The toughness of the diet of the TSN monkey was also found to exceed that of other SE Asian colobines at the Endangered Primate Rescue Center, Cuc Phuong, Vietnam.

These dietary findings, when coupled with preliminary data on masticatory morphology, reveal unexpected ecomorphological relationships among members of the genus Rhinopithecus that we are examining in greater detail.

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Tonkin snub-nosed monkey, Rhinopithecus avunculus, endemic, dietary ecology, Vietnam