Using hammers to crack nuts (nut-cracking) in chimpanzees is often considered one of the most complex tool-use behaviours observed in primates. Indeed, nut-cracking is characterised by various features that differentiate it from other chimpanzee tool-use behaviours, including the potential requirement for the development of the behaviour within a sensitive learning window. 

In collaboration with Claudio Tennie, this project examines the development of nut-cracking in captive chimpanzees that are still within the sensitive learning window (2-6 years old) for this behaviour, without the provision of demonstrations on the behaviour. To do so, we are testing motivated, unenculturated, untrained, and nut-cracking-naïve chimpanzees that are within their proposed sensitive learning window across several zoos around the globe. Following a motivational introduction and test, these chimpanzees are provided with all the raw materials for nut-cracking, but no demonstrations on the know-how involved. This long-term baseline, which takes place over approximately one year, allows us to track the gradual emergence of nut-cracking behaviours in juvenile chimpanzees.