These photos show a Red Langur eating a ripe female Ficus lepicarpa fig.
The normal diet of langurs in Borneo is the young leaves and unripe seeds of a very wide a variety of trees and shrubs, especially the leaves of plants in the pea family (Leguminosae) e.g. Spatholobus a very common hanging vine.
Langurs rarely eat ripe fruit because the sugars in ripe fruit ferment inside the langur’s stomachs and the resultant carbon dioxide gas causes the stomach to bloat sometimes killing the langur.
Recent records show that Ficus lepicarpa a common small tree of the forest edge is a favourite food of Red Langurs. Red Langurs eat the young leaves, the unripe figs and the ripe figs. However the ripe figs are eaten very very slowly with the langur biting of one small piece after another. As the entrance to the stomach is very narrow in langurs it appears that langurs probably chew even the ripe fig seeds and therefore Red Langurs are seed predators of figs whereas macaques, gibbons and orangutans are seed dispersers of figs.
Photos and information provided by Shavez Cheema and Chun Xing WONG of 1Stop Borneo Wildlife.