Why Taï mangabeys do not use tools to crack nuts like sympatric-living chimpanzees: a cognitive limitation on monkey feeding ecology

Abstract

Nuts are high in energetic and nutritional value, but the kernel inside is difficult to access. In the Tai forest, it is estimated that chimpanzees (Pan troglodytes verus) can eat 6–10 times as many nuts with the help of a tool as to when they crack them with their own teeth. However, sympatric-living terrestrial monkeys never crack nuts using tools. So this begs the question, why not? In this chapter, we report on the foraging behaviour of the sooty mangabeys (Cercocebus atys atys). A quick synopsis goes as follows: they observe nut-cracking chimpanzees at a distance of 5–10 metres, relish in the leftovers of the freshly cracked nuts, and then continue to follow the chimpanzees to different nut-cracking sites. With this information, we go on to consider the underlying reasons for the absence of nut-cracking in sooty mangabeys, with a particular focus on cognitive limitations, and then discuss the implications of field observations for studies on imitation in the laboratory.