A new five-year study has revealed that wild chimpanzees in West Africa may be using stones to communicate with one another.
This remarkable behavior, documented by researchers from Wageningen University & Research and the German Primate Research Center, offers new insight into how these animals interact—and how their behaviors might be more complex and human-like than we once thought.
The study took place in Guinea-Bissau, where researchers set up camera traps in a protected nature reserve.
With help from local field guides, they recorded chimpanzees at five different locations.
At certain sites, the team noticed a curious pattern: adult male chimpanzees were seen repeatedly throwing or striking stones against the trunks of trees.
Over time, this created small piles of stones at the base of these trees—evidence that this wasn’t just random behavior.
Lead researcher Sem van Loon describes this activity as “stone-assisted drumming.”
It’s similar to a well-known chimpanzee behavior where they drum with their hands or feet on hollow tree roots, usually to communicate over long distances or to show dominance. But this new behavior is a little different.
In traditional drumming, the chimpanzees are usually quiet before making noise. In contrast, with stone drumming, the chimps often make loud “pant-hoot” calls before suddenly going silent and then throwing the stone.
Van Loon believes the purpose may also be different. She suggests that the sound of a stone hitting a tree may travel farther through dense forest than other kinds of noise, making it a more effective way for chimps to send a message over long distances.
What’s especially fascinating is that this behavior seems to be passed down through learning. Younger chimps copy the behavior from older ones, meaning it’s not something they are born knowing—it’s part of their culture. This kind of social learning is something we once believed only humans did.
Professor Marc Naguib, who specializes in behavioral ecology, says this discovery reminds us that culture isn’t exclusive to humans. Chimpanzees also pass down learned traditions, and that’s something conservation efforts should recognize and protect.
The study, published in the journal Biology Letters, opens up new questions about how animals communicate and how complex their social lives may really be.
