Why Do Male Chimpanzees Throw Rocks at the Same Trees for More Than a Decade?
Nautilus · 2026-09-02
Wild western chimpanzees, usually adult males, engage in accumulative stone throwing, a rare and potentially cultural behavior observed in four groups in West Africa. This involves throwing rocks at specific trees and repeatedly returning to these sites, often accompanied by pant hooting and buttress drumming. Researchers, including Ammie Kalan and Robyn Nakano, studied this phenomenon in Guinea-Bissau, using camera traps to collect data on unhabituated chimpanzees. Their findings indicate that these sites can be used for over a decade.
This behavior is considered a modification of common male chimpanzee displays and suggests a form of complex communication or even symbolic purpose, potentially marking important territorial locations. However, the exact meaning to the chimpanzees themselves remains unknown. The research aims to understand the social and ecological context of this behavior, hoping it sheds light on the emergence of complex communication and stone tool use in human evolution. Such cultural behaviors are vital for chimpanzee conservation, especially as their habitat in Guinea-Bissau faces threats from extractive industries like bauxite mining, which can cause habitat destruction and pollution.