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Chimpanzee hand axe3/11/2023 Not only do some chimpanzee populations use stone tools comparable to hominin stone-knapping, but many of their artefacts are made of perishable material such as sticks and grass, which, if used by our ancestors, would not have fossilised and therefore would remain unknown. Studying the artefacts left behind by chimpanzees is especially important to understand hominin traditions in the fossil record. In order to improve our understanding of how culture evolved among our hominin ancestors, we must document the traditions of as many chimpanzee populations as possible and the species-wide variation therein. The rich behavioural diversity of our evolutionary cousin, the common chimpanzee ( Pan troglodytes), provides an exception and has been argued to represent a form of non-human culture. This diversity can be contrasted with the socially learned traditions of other species, such as songbirds, bowerbirds (Ptilonorynchidae), New Caledonian crows ( Corvus moneduloides) and cetaceans, which appear to be limited to one or a few behavioural domains. When seen in the context of animal traditions, human culture stands out: it permeates every aspect of our lives, spanning behavioural domains ranging from tool-making and dietary preferences to language, fashion and art. Possible explanations for this pattern are a recent chimpanzee expansion across the region and the interconnectedness of this population across at least the entirety of northern DRC. We propose that this widespread and related suite of behaviours be referred to as the Bili-Uéré Chimpanzee Behavioural Realm. Our results allow us to describe a new chimpanzee behavioural complex, characterised by a general similarity of multiple behaviours across a large, ecologically diverse region but with subtle differences in prey choice and techniques. This lack of evidence is consistent with the results of dung washes, which revealed a substantial proportion of driver ants, but no evidence of Macrotermes or other termites. We found no evidence of termite-fishing, despite the availability of Macrotermes muelleri mounds throughout the region. We encountered some geographic variation in behaviour: we found honey-digging tools, long driver ant probes and fruit-pounding sites only to the north of the Uele River there were more epigaeic Dorylus tools to the north and more ponerine ant tools to the south. and Thoracotermes macrothorax and hard-shelled fruits such as Strychnos, along with evidence of the pounding open of African giant snails and tortoises. We describe two potential new tool types, an “ant scoop” and a “fruit hammer.” We document an extensive percussive technology used to process termite mounds of Cubitermes sp. Tools classified as terrestrial honey-digging sticks were a significant predictor for brushed and blunted tool ends, consistent with their presumed use. ![]() Epigaeic Dorylus tools were significantly longer than the other tool types, and D. kohli and stout digging sticks used to access underground meliponine bee nests. We describe a new chimpanzee tool kit: long probes used to harvest epigaeic driver ants ( Dorylus spp.), short probes used to extract ponerine ants and the arboreal nests of stingless bees, wands to dip for D. Over a 12-year period, we documented chimpanzee tools and artefacts at 20 survey areas and gathered data on dung, feeding remains and sleeping nests. Here we describe the insect-related tool technology of Bili-Uéré chimpanzees ( Pan troglodytes schweinfurthii) inhabiting an area of at least a 50,000-km 2 area in northern DRC, as well as their percussive technology associated with food processing. About half of the world’s remaining chimpanzees ( Pan spp.) live in the Democratic Republic of Congo (DRC), yet until now we have known almost nothing about their behaviour. To improve our understanding of the evolutionary origins of culture and technology in humans, it is vital that we document the full extent of behavioural diversity in our great ape relatives.
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