Diet of the Annamese langur (Trachypithecus margarita) (Elliot, 1909) at Takou Nature Reserve, Binh Thuan Province, Vietnam

The Annamese langur (Trachypithecus margarita) was described in 1909 but its ecology, including its feeding behaviour, is still largely unknown. Based on current knowledge of feeding ecology of many Asian langurs, T. margarita is expected to be a generalist herbivore, with seasonal variation in diet. Feeding behaviour of one habituated group of Annamese langurs at Takou Mountain was studied from October 2009 to September 2011. The dietary pattern of these langurs was found to be similar to other Trachypithecus species, which is characterised by a high amount of leaf consumption (54.4% immature leaves, 7.1% mature leaves) and complemented by fruits (29.9%). The Annamese langurs ate plant parts from 31 species belonging to 20 families on Takou Mountain where 689 plant species were known for the mountain. Moraceae is the most important family in the langur's diet with at least 10 species consumed and accounting for 41.1% of feeding time. Based on the current and previous feeding studies of Trachypithecus species, it could be concluded that the genus is a generalist folivore and the dietary pattern is similar among species.