Isotopic studies conducted on chimpanzee populations have established the species firmly in the C 3 feeding category, meaning that in all habitats chimpanzees primarily feed on tree products that utilise a C 3 photosynthetic pathway 20, 21, 22, 23. Unlike forest-dwelling chimpanzees, savannah chimpanzees tend to incorporate and rely upon many non-fruit items 19. In fact, data on the mechanical properties effectively hail from one tropical forest 18, and it is doubtful these values accurately reflect the dietary variance of the species. Currently our understanding of chimpanzee dentition and its functional aspects are limited by a lack of data on the broader dietary mechanical challenges faced species-wide 16, 17. The tropical forest is analogous to the original stem hominin habitat 14, whilst in comparison the savannah woodland mirrors the ecological conditions that drove later hominin adaptation and the emergence of Homo 15 (Fig. Therefore, comparative studies of ingestive behaviours and food mechanical properties in large bodied apes, like chimpanzees, are essential to fully understand relationships between craniodental form and function in fossil hominins.Ĭhimpanzees allow for an interesting comparison of feeding in two evolutionarily relevant hominin habitats. The mismatch between the mechanical characteristics of foods and how they are processed orally often makes it difficult to understand the physical conditions that foods exert on teeth and can lead to an oversimplification of this vital interface. Such processing is termed ingestion, which is often facilitated by the anterior dentition and is distinct from mastication, where food is cyclically processed by posterior dentition before being swallowed 13. The mechanical properties of such tissues can vary substantially and can instigate distinct oral feeding practices. In addition, accessing foods often includes the removal of external tissues with the teeth to access the nutrients within. However, in such studies, foods are still largely categorised in very broad terms (e.g., fruits, leaves, bark) that do not faithfully track their mechanical properties 12. In chimpanzees ( Pan troglodytes), direct behavioural observation and indirect methods such as isotopic and faecal analysis have allowed a rather in-depth knowledge of what their diets are composed of 2, 3, 4, 5, 6, 7, 8, 9, 10, and thus allow for some comparison with the putative diets of the earliest hominins 11. Understanding how the form of teeth relates to their function therefore requires a synthesis of knowledge over both tooth structure and the mechanical properties of the critical foods that resist being broken down 1.
#Food habits of chimpanzees driver
Food mechanics are likely a substantial driver in the adaptation of the dental complex and the constraints that these place on the efficiency of food processing. Nowhere is this more salient than in the evolution of the hominin tribe and the emergence of modern day humans, as the majority of dietary inferences must be constructed from a patchwork of fossilised craniodental remains.
Similarly, these data can help clarify the dietary mechanical landscape of extinct hominins often overlooked by broad C3/C4 isotopic categories.ĭiet is integral to understanding the behaviours and adaptations of extant and extinct primate species alike. These findings demonstrate that chimpanzee foods in some habitats are mechanically more demanding than previously thought, elucidating the broader evolutionary constraints acting on chimpanzee dental morphology. This pattern is concurrent with different isotopic signatures between sites. We show that foods at Issa can present a considerable mechanical challenge, most saliently in the external tissues of savannah woodland plants compared to their tropical forest equivalents. Here we combine measures of dietary mechanics with stable isotope signatures from eastern chimpanzees living in tropical forest (Ngogo, Uganda) and savannah woodland (Issa Valley, Tanzania). Field observations and isotopic analyses suggest that environmental conditions greatly affect habitat resource utilisation by chimpanzee populations. Chimpanzees are traditionally described as ripe fruit specialists with large incisors but relatively small postcanine teeth, adhering to a somewhat narrow dietary niche.
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