Presbytis – Surilis

The genus Presbytis is a group of Old World monkeys found primarily in the tropical rainforests of Southeast Asia, including Indonesia, Malaysia, southern Thailand, and Brunei. These primates are small, slender, and arboreal (tree-dwelling), adapted to life in the forest canopy. What makes them particularly fascinating is their leaf-based diet, graceful movements, and often striking facial features, which vary significantly from species to species.

Presbytis monkeys are generally light-bodied, with long limbs and even longer tails used for balance as they move through the treetops. Their fur colors range from gray, black, and brown to white or reddish tones, often with contrasting patches on the face, chest, or limbs. Many species have distinctive facial markings, such as white eye rings, bushy beards, or sharply outlined eyebrows, giving them expressive and sometimes comical appearances.

One of the defining traits of the genus is their highly specialized digestive system, adapted for a folivorous (leaf-eating) diet. Like cows, they have a complex stomach that helps break down tough plant material through fermentation. This allows them to extract nutrients from leaves, flowers, unripe fruits, and other fibrous vegetation that many other primates avoid. Because this diet is low in calories, Presbytis monkeys spend much of their day resting or slowly foraging through the canopy.

Most Presbytis species live in small, tight-knit groups, often made up of one adult male, several females, and their offspring. These groups are territorial and communicate through vocal calls, body postures, and facial expressions. Males make loud, resonant calls that echo through the forest to mark territory or warn off rivals. The bonds between mothers and infants are particularly strong, with babies often seen clinging tightly to their mothers as they leap through the trees.