Subsistence Technology of Nigerian Chimpanzees

Abstract

A trademark of Homo sapiens is the enormous variation in behavioral patterns across populations. Insight into the development of human cultures can be aided by studies on communities of Pan across Africa that display unique combinations of social behavior and elementary technology. Only cross-population comparisons can reveal whether the diversity reflects differential genetics, environmental constraints, or is a cultural variant. However, the recently recognized and most endangered subspecies, Pan troglodytes vellerosus, remains completely unstudied in this respect. We report first evidence from a new long-term study of Nigerian chimpanzees at Gashaka. Their dietary composition is highly varied and they have to cope with high concentrations of antifeedant defenses of plants against consumption. Gashaka chimpanzees use a varied tool kit for extractive foraging. For example, they harvest insects throughout the year, via digging sticks and probes, to obtain honey from stingless-bee and honeybee nests, dipping wands to prey on army ants, and fishing rods to eat arboreal ants. Tools appeared to be custom-made with a considerable degree of standardization in length, diameter, and preferential use of distal ends. Moreover, compared to the rainy season, tools were longer during the dry season when insects retreat further into their nests. Many of the expressions of subsistence technology seem to be environmentally constrained. Most notably, the absence of termite-eating could reflect a low abundance of mounds. Other traits may represent cultural variation. For example, the chimpanzees did not hammer open 2 types of hard-shelled nuts with tools, unlike what occurs elsewhere in West Africa. The prevalence of elementary technology may indicate that the material culture of Gashaka chimpanzees is most related to core cultural tendencies of Central African populations.