Similar to humans, chimpanzees use communication to coordinate their cooperative behavior, such as during hunting. When chimpanzees produce a specific vocalization, called a “hunting bark,” they recruit more group members for hunting and capture prey more efficiently, researchers from the University of Zurich and Tufts University have shown.
Chimpanzees don’t just look for fruit, they also occasionally look for situations to acquire protein-rich meat. To catch their agile monkey-like prey in the canopy, chimpanzees had better have hunting companions by their side. Scientists have discovered for the first time that interaction is essential for recruiting group members to join the hunt.
Hunting barks make pursuit more effective
By studying more 300 hunting events recorded over the past 25 years within the Kanyawara chimpanzee community in Uganda, researchers from the University of Zurich (UZH) and Tufts University in Boston found that by emitting bark vocalizations, wild monkeys catalyze group hunting, making this form of cooperative behavior more effective. “Chimpanzees that produce hunting barks provide information to those nearby about their determination to hunt, and this information can persuade reluctant individuals to join, increasing the overall odds of success,” says Joseph Mine, PhD student at the Department of Comparative Language Sciences of UZH. who conducted the study.
Hunting monkeys in groups in dense tropical rainforest where visibility is restricted can be difficult. Voice chat allows for more effective group work. “Surprisingly, following the production of hunting barks, we observed more hunters joining, greater speed to start the hunt, and a shorter docket time to make the first capture,” explains the co-final author of study Zarin Machanda of Tufts University, who leads the Kanyawara Chimpanzee Project.
Although hunts are most effective after a bark, more research is needed to find out why barking has this effect. “At this time, it remains unclear whether these barks are given intentionally to coordinate the precise steps of the group, or whether these barks simply announce an individual’s decision to hunt, which, in turn, increases the likelihood that others join them and with more hunters. they are more effective,” adds UZH professor Simon Townsend, who helped lead the study. Co-evolution of conversation and cooperation
Evolutionary biologists considered a wide range of other factors that could affect the outcome of a hunt, including the presence of skilled hunters as well as potential distractions, but the presence of hunting barking retained a key role. “Conversation plays a key role in coordinating complex acts of cooperation in humans, and this is the first indication that voice communication may also facilitate group cooperation in our closest living parents,” says Townsend.
It is widely accepted that interaction and cooperation are closely related and co-evolved in humans. Over time, as one became more complex, the other became the same, generating a cycle of feedback that eventually led to the particularly complex language and forms of cooperation in which modern humans engage.
Evolutionary roots at least 7 million years old
However, it was not known how far into the evolutionary past of humans this relationship between group cooperation and communication can be traced. Joseph Mine concludes: “Our results indicate that the relationship between vocal communication and cooperation at the group level is ancient. This link appears to have been in place for at least 7 million years, since our last common ancestor with chimpanzees.”