Inoue-Nakamura, N, & Matsuzawa, T (1997) Development of stone tool use by wild chimpanzees (Pan troglodytes). Journal of Comparative Psychology, Vol.111, No.2, Pp.159-173.
Since 1987 at Bossou in Guinea in West Africa, observations have been being made in the centre of free- range area, where experimenters provide stones and nuts.
Chimpanzees of Bossou are well known for using a stone hammer and anvil to crack open the nuts of the oil palm tree (Elaeis guineensis | description of palm fruit ).
Nut cracking consists of the following actions:
The individual actions of ‘Take’, ‘put’ ‘hold’, ‘hit’ and eat, had all been performed by 1.5 yrs
At 2.5 they often put a nut on a stone, hit it with the back of their hand, then picked up a kernel from somewhere else or scrounged a kernel from their mothers
Holding the hammer was the a difficult part – chimps never hit nut with the hammer stone until the last stage.
“True imitation cannot explain the results of the present study. The infants showed a variety of fundamental actions. They gradually increased the relative frequency of adequate sequences of the basic actions through each stage of development. They did not copy the motor patterns or the way to relate nuts with stones………. As the present results suggest, they learned the general functional relations of stones and nuts and also learned the goals obtained by the demonstrator. This learning process might be called emulation.” (p.172).
Chimpanzees are predominantly fruit-eating, but they also eat a variety of other foods. So far, we have observed that fruits, leaves, flowers, seeds, pith, bark, gum, sap, mashrooms, insects, honey, bird eggs, owls, and tree pangolins are included in food repartoire of Bossou chimpanzees. You can observe below chimpanzees feeding on figs, one of the most important foods for them.
Chimpanzees make and use a diverse and rich kit of tools and, with the exception of humans, they are the only living primates to consistently and habitually use and make tools.