In addition to leaves, Proboscis monkeys may consume fruits from time to time, with particular preferences for figs, rambutans, and mulberries. Although fruit consumption contributes to their diet, it is not as consistent as leaf consumption. Occasionally, they are also known to feed on insects such as ants and termites, providing a source of protein.
It's important to note that the diet of Proboscis monkeys can vary depending on the specific habitat they reside in and the availability of food sources. However, their diet is primarily focused on leaves and plant material.