At a Glance
- Chimpanzees in Guinea-Bissau have been observed striking stones against tree trunks to create loud sounds, forming stone piles that may represent a unique form of acoustic communication.
- Researchers used camera traps for five years to document this behavior alongside vocalizations like pant-hoots, suggesting that stone-assisted drumming is a long-distance signaling method.
- Unlike traditional drumming, chimps struck stones after vocalizing, producing low-frequency sounds capable of traveling farther through dense forest environments to assert presence or dominance.
- The behavior is culturally transmitted, with young chimpanzees learning the stone-striking practice by observing older group members within their social groups.
- These findings challenge long-held beliefs about animal culture, indicating that non-human species like chimpanzees also engage in socially learned behaviors that warrant consideration in conservation strategies.
Chimpanzees are known for their complex communication methods, which include vocalizations and physical actions, such as hand and foot drumming on tree trunks. A recent study by behavioral biologists in Guinea-Bissau has uncovered an unusual new behavior: chimpanzees using stones to produce sounds by striking them against tree trunks, creating piles of stones at the base of trees. This behavior has sparked interest, as it could represent a form of communication distinct from traditional methods.
Over five years, researchers from Wageningen University & Research and the German Primate Research Center used camera traps to observe chimpanzee behavior at five locations in a nature reserve. They found that the stone-striking behavior often occurred with loud vocalizations, particularly pant-hoots, and resulted in stone piles at tree trunks. The findings, published in Biology Letters, suggest that this “stone-assisted drumming” may serve as a long-distance communication tool, similar to the drumming behavior produced by chimps using their hands and feet on tree trunks.
Lead author Sem van Loon explained that while the stone behavior shares similarities with traditional drumming, there are key differences. For instance, chimpanzees struck the stones after emitting loud pant-hoots, a behavior opposite to typical drumming often preceded by silence. The loud, low-frequency sounds created by the stone hits might be designed to travel further across dense forests, allowing chimpanzees to communicate over long distances or to display dominance.
The researchers also observed that this behavior appears to be learned through social interaction rather than instinct. Young chimpanzees adopted the stone-striking behavior from older group members, indicating that the practice is passed down culturally. This discovery challenges our understanding of culture in animals, suggesting that behaviors once thought unique to humans, like cultural transmission, also occur in the animal kingdom and should be considered in conservation efforts.
References
- Wageningen University. (2025, May 26). Five-year study suggests chimpanzees strike stones against trees as form of communication. Phys.Org; Wageningen University. https://phys.org/news/2025-05-year-chimpanzees-stones-trees-communication.html
- Van Loon, S., Heitkönig, I. M. A., Goedmakers, A., Mundry, R., & Naguib, M. (2025). Stone-assisted drumming in Western chimpanzees and its implications for communication and cultural transmission. Biology Letters, 21(5), 20250053. https://doi.org/10.1098/rsbl.2025.0053
