Supplementary Material S1: Observed drinking behaviour in primates from water-filled tree holes.

Water is an indispensable source of all life forms on Earth, vital to many physiological and environmental processes. Like all animals, folivore primates depend on supplemental water to maintain hydration, constrained by a leaf-based diet containing high fibre content and stored secondary compounds; however, such reports are scarce from wild populations. Here, we report an opportunistic sighting of water ingestion by a troop of Capped langur, Trachypithecus pileatus, from a tropical forest fragment during the wet season from water accumulated in a tree hole, and end with a note advocating its importance in forest management plans. Understanding their significance can guide conservation efforts.