Mysterious Chimpanzee Stone Throwing Ritual

In the above video you will see a large male chimp approaching a tree. He pauses for a second, then glances around, grabs a huge rock and flings it full force at the tree trunk. We have known about this. Prior studies have shown or provided anecdotes of wild chimpanzees throwing and banging stones in Liberia, Guinea, and Guinea-Bissau stone throwing with implications that they might be ritual. The behavior ranges from carefully placing stones inside hollow trunks to full-on hurling.

(a) Adult male chimpanzee tossing a stone; hurling a stone (Boé, Guinea-Bissau); and banging a stone (Comoé GEPRENAF, Côte d’Ivoire). (b) Boé, Guinea-Bissau landscape: stones accumulated in a hollow tree; a chimpanzee accumulative stone throwing site; and stones accumulated in-between buttress roots.

A Nature published study indicates that these are not random, one-off events. The authors suggest they are repeated activities without a clear link to gaining food or status. This all implies ritual behavior. The authors many other sites where trees had similar markings and in many places piles of rocks had accumulated inside hollow tree trunks.

This could be part of a male display, with a loud bang against a trunk as a sign of impressive  strength. But, on the other hand, it could be more symbolic than that, as a form of marking pathways and territories with signposts such as piles of rocks. Figuring out where chimps’ territories are in relation to rock throwing sites could give us insights into whether this is the case here. What do you think this symbolizes?