Object manipulation and tool use in Nicobar long-tailed macaques (Macaca fascicularis umbrosus)

Abstract

Object manipulation and tool use by non-human primates have received considerable attention from primatologists and anthropologists, because of their broad implications for understanding the evolution of tool use in humans. To date, however, most of the studies on this topic have focused on apes, given their close evolutionary relationship with humans. In contrast, fewer studies on tool use and object manipulation have been conducted on monkeys. Documenting and studying object manipulation and tool use in species that are more distantly related to humans can provide a broader perspective on the evolutionary origins of this behaviour. We present a detailed description of toolaided behaviours and object manipulation by Nicobar long-tailed macaques ( Macaca fascicularis umbrosus ) living along the coastlines of Great Nicobar Island. We made observations from December 2018 to March 2019, using ad libitum and focal sampling methods. We observed behaviours related to object manipulation and tool use in six different behavioural contexts (foraging, hygiene, communication, play, selfdirected and self-hygiene behaviour) involving eight different types of objects, namely resonance rod, play object, rolling platform, scraping tool, dental groom, pounding substrate, leaves as grip pads and wipers, and stimulation tool. We observed that males were involved in tool use and object manipulation more frequently than females. Our results add to existing records of object manipulation, tool-use behaviour and tool variants displayed by non-human primates, showing that Nicobar macaques perform multiple and diverse tool-aided behaviours.