van Loon Sem, Heitkönig Ignas M A, Goedmakers Annemarie, Mundry Roger, Naguib Marc
Behavioural Ecology Group, Wageningen University, Wageningen, The Netherlands.
Wildlife Ecology and Conservation Group, Wageningen University, Wageningen, The Netherlands.
Biol Lett. 2025 May;21(5):20250053. doi: 10.1098/rsbl.2025.0053. Epub 2025 May 7.
Chimpanzees () communicate in complex ways, including sounds produced by hand and foot drumming on trees, often combined with loud vocalizations. Recently, a puzzling stone throwing behaviour at trees was observed, resulting in stone piles at tree buttresses. It is a rare case of tool used for communication in animals and suggested to function like buttress drumming in long-distance communication and male displays. We tested this hypothesis by determining the behavioural dynamics in comparison to hand and foot tree buttress drumming in Western chimpanzees in Boé, Guinea Bissau. Using camera traps, we show that in 78% of cases, stones were picked up at trees, not leading to further stone accumulation beyond the already existing stone piles. Stone-assisted and hand and foot drumming occurred separately or were combined in similar behavioural contexts in apparent long-distance communication and highly aroused behavioural contexts. Yet, immediately before stone drumming, chimpanzees swayed less and pant-hooted more while afterwards pant-hooting less compared to the other contexts, suggesting a separate motivation and/or function for stone-assisted drumming. It suggests this unique stone-based activity has its own signal value, separate from hand/foot buttress drumming and, considering the spatial variation, might be culturally transmitted.
黑猩猩以复杂的方式进行交流，包括用手和脚拍打树木发出声音，这些声音通常还伴随着响亮的叫声。最近，观察到一种在树上投掷石块的令人费解的行为，导致树基部出现石堆。这是动物中罕见的用于交流的工具使用案例，有人认为其功能类似于在远距离交流和雄性展示中的基部拍打。我们通过确定几内亚比绍博埃地区西部黑猩猩与用手和脚拍打树基部行为相比的行为动态来检验这一假设。利用相机陷阱，我们发现，在78%的情况下，石块是在树上捡起的，不会导致在已有的石堆之外进一步堆积石块。在明显的远距离交流和高度兴奋的行为情境中，用石块辅助以及用手和脚拍打行为分别出现或结合出现。然而，与其他情境相比，就在用石块拍打之前，黑猩猩摆动得更少，喘气叫声更多，而之后喘气叫声更少，这表明用石块辅助拍打有单独的动机和/或功能。这表明这种独特的基于石块的活动有其自身的信号价值，与用手/脚拍打树基部不同，并且考虑到空间差异，可能是通过文化传承的。
