Why do chimpanzees throw stones at trees?

Chimpanzees often use tools to extract or consume food. Which tools they choose for which purpose, however, can differ depending on the region where they live. Researchers of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have thus initiated the ‘Pan African Programme: The Cultured Chimpanzee’ and, since 2010, have collected data on chimpanzee behavior, demography and resource availability across Africa following a standardized protocol. This is how the researchers encountered a thus far unknown behavior: In West Africa chimpanzees throw stones at trees resulting in conspicuous accumulations at these sites. Why exactly the animals do this the researchers do not yet know, yet the behavior appears to have some cultural elements. More information: