Chimpanzee cultures differ between neighbors

Despite similar ecological conditions neighboring chimpanzee groups use different hammers to crack nuts

Culture has long been proposed to be a distinguishing feature of the human species. However, an increasing amount of evidence from the field has shown that in several animals, differences in behaviors between populations actually reflect the presence of culture in these species. These studies have mainly come from populations that live far apart from each other which make it difficult to exclude ecological or genetic differences as being the underlying reasons for the observed behavioral differences. Now for the first time, cultural differences between directly neighboring chimpanzee groups have been found in the wild and are reported by Lydia Luncz, Roger Mundry and Christophe Boesch of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

The Taï chimpanzee project field site in Côte d’Ivoire presents the unique opportunity to study three neighboring chimpanzee communities at the same time, making it possible to directly compare the behaviors present in each community. Chimpanzees in Côte d’Ivoire use stone and wooden tools to crack nuts. Lydia Luncz was therefore able to observe how the chimpanzees were selecting hammers to crack Coula nuts in the three adjacent communities. After placing gathered Coula nuts on root anvils, the chimpanzees of all three neighboring communities primarily select stones to use as hammers. However, as the nut season advances and nuts get drier and easier to crack, the chimpanzees of two of the communities select a greater proportion of wooden hammers which are easier to find in the forest, while the members of the third community continue to favor stone hammers. Furthermore, the two communities that select wooden hammers choose distinctly different sized hammers. All of the chimpanzees live in a contiguous stretch of the large Taï National Park and therefore ecological differences are unlikely to explain the differences in tool selection.

"In humans, cultural differences are an essential part of what distinguishes neighboring groups that live in very similar environments," said Lydia Luncz of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, the lead author of the paper. "For the first time, a very similar situation has been found in wild chimpanzees living in the Taï National Park, Côte d’Ivoire, and this demonstrates that they share with us the ability for fine-scale cultural differentiation."

"In many ways, chimpanzees are very similar to us humans," Christophe Boesch said, the director of the Taï chimpanzee project, and co-author of the paper. "By studying the similarities to our closest living relatives in their natural habitat in Africa, we have the opportunity to learn more about the evolutionary roots of culture, which is for us humans one of the key elements of our identity."

Certainly more can be learned about the cultural abilities of chimpanzees in the wild by studying this specific population. Therefore, Lydia Luncz will be returning to Côte d’Ivoire early next year to study different aspects of the cultural life of the Taï chimpanzees. Time is of the essence, however, as chimpanzees are threatened across their natural range. Further, a great deal of chimpanzee cultural variation must have vanished over the last few decades, as 90% of the chimpanzee populations in Cote d’Ivoire have disappeared over the last 20 years. The Wild Chimpanzee Foundation was created by Christophe Boesch to enhance the survival of the remaining wild chimpanzee populations and their habitat, the tropical rain forest, throughout tropical Africa.