Chimpanzee Tool Usage

Chimpanzees from the Tai forest of Cote d'Ivoire produce unintentional flaked stone assemblages at nut-cracking sites, leaving behind a record of tool use and plant consumption that is recoverable with archaeological methods. About 40 kilograms of nutshell and 4 kilograms of stone were excavated at the Panda 100 site. The data unearthed show that chimpanzees transported stones from outcrops and soils to focal points, where they used them as hammers to process foodstuff. The repeated use of activity areas led to refuse accumulation and site formation. The implications of these data for the interpretation of the earliest hominin archaeological record are explored. (Joulian: 173-189)

Ape ethoarchaeology uses primatological data to formulate archaeological hypotheses. For example, several authors have studied stone tools used by chimpanzees for nut cracking and have discussed similarities between them and early hominin tools. This paper reports on the nature and content of a naturally buried stone assemblage produced by the nut-- cracking activities of chimpanzees (Pan troglodytes) in the wild. We describe the behavioral data unearthed at the chimpanzee stone tool site of Panda 100 (hereafter P100) at Tai National Park, Cote d'Ivoire, which was excavated with the same techniques that are applied to the recovery of early archaeological sites and yielded preserved activity areas containing a large amount of plant refuse and 479 stone pieces. (McGrew: 106)

Several West African chimpanzee populations use stone tools to crack open hard-- shelled nuts. Nut-cracking technology allows chimpanzees to obtain more than 3000 calories per day and has been extensively studied at Tai National Park, Cote d'Ivoire At Tai, chimpanzees are known to crack nuts from Panda oleosa, Coula edulis, Parinari excelsa, Sacoglottis gabonensis, and Detarium senegalense. On soft shells (such as those of Coula), chimpanzees use both soft and hard hammers, but access to Panda oleosa (abbreviated as Panda) seeds requires the use of stone hammers. Panda kernels are the toughest in sub-Saharan Africa, require an average compression force of 1100 kg to crack open, and contain three seeds . Panda trees rarely cluster, and they grow in undisturbed lowland forest along valley bottoms and swamps. The average distance between Panda trees across the site and the surrounding 30 hectares is ~100 m.

The nut-cracking season for the Tai chimpanzees is from February to August. A single chimpanzee may crack up to 100 fruits in one day, and refuse heaps form at processing locations around anvils. Learning to crack Panda nuts takes up to 7 years , and females crack more often than males. Typically, chimpanzees use stone hammers of igneous rocks (weighing 3 to 15 kg) and lateritic soil crust (weighing up to 6 kg) on nonmovable anvils that are used repeatedly over time, such as roots from hardwood trees and outcropping rocks. The stones used as hammers are obtained from local igneous outcrops and ferralitic soil exposures and are then taken to processing locations within nut-cracking sites. These hammers are curated intensively and transported between nut-cracking sites, sometimes involving distances of several hundred ...