Tool-assisted water scooping in Balinese long-tailed macaques

While tool use has been widely reported in non-human animals for food acquisition, the use of tools for drinking has been largely overlooked, with primates being a notable exception. We documented tool-assisted water scooping and drinking in several Balinese long-tailed macaques (Macaca fascicularis), living in Ubud, Indonesia, over a period of four years. We observed repeated tool-assisted water scooping using leaves, nuts, pits, and stones. Our results indicate that this behaviour is associated with manual drinking and can be performed in a playful context. This population habitually engages in a cultural form of stone-assisted object play known as stone handling, and it has an overall propensity to manipulate objects in water. We discuss the relationship between instrumental and non-instrumental object-assisted actions, as well as the possibility for this behaviour to be a tradition in this population. This report offers new insights into the limited literature on tool-assisted drinking in monkeys.