Flexible and Persistent Tool-using Strategies in Honey-gathering by Wild Chimpanzees

Several populations of wild chimpanzees use tools to raid bee nests, but preliminary observations of chimpanzees in the Congo Basin indicate that they may have developed sophisticated technical solutions to gather honey that differ from those of apes in other regions. Despite the lack of habituated groups within the range of the central subspecies, there have been several reports of different types of tools used by chimpanzees to open beehives and gather honey. Researchers have observed some of these behaviors (honey dipping) in populations of western and eastern chimpanzees, whereas others (hive pounding) may be limited to this region. Toward evaluating hypotheses of regional tool using patterns, we provide the first repeated direct observations and systematic documentation of tool use in honey-gathering by a population of Pan troglodytes troglodytes. Between 2002 and 2006, we observed 40 episodes of tool use in honey-gathering by chimpanzees in the Goualougo Triangle, Republic of Congo. Pounding was the most common and successful strategy to open beehives. Chimpanzees at this site used several tools in a single tool-using episode and could also attribute multiple functions to a single tool. They exhibited flexibility in responses toward progress in opening a hive and hierarchical structuring of tool sequences. Our results support suggestions of regional tool using traditions in honey-gathering, which could be shaped by variation in bee ecology across the chimpanzee range. Further, we suggest that these chimpanzees may have an enhanced propensity to use tool sets that could be related to other aspects of their tool repertoire. Clearly, there is still much to be learned about the behavioral diversity of chimpanzees residing within the Congo Basin.