Communication by chimpanzees improves cooperative hunting success

July 29, 2022

Chimpanzees don’t only forage for fruit; from time to time they also seek out opportunities to acquire protein-rich meat.

To catch their agile monkey prey in the canopy, chimpanzees are better off having companions hunting alongside them. And to be especially successful, new research published this week in Science Advances indicates that communication is key. chimpanzee hunting monkeys in a tree Chimpanzees hunting in the tree canopy. Photo by Ian Gilby/ASU

Similar to humans, chimpanzees use communication to coordinate their cooperative behavior — like during hunting. When chimpanzees produce a specific vocalization, known as the “hunting bark,” they recruit more group members to the hunt and capture their prey more effectively.

Hunting barks make the chase more effective

By studying more than 300 hunting events recorded over the last 25 years at the Kanyawara chimpanzee community in Uganda, researchers — including ASU primatologist Ian Gilby — have discovered that by making bark vocalizations, the wild apes catalyze group hunting, rendering this form of cooperative behavior more effective.

Gilby is a research associate with the Institute of Human Origins and associate professor in the School of Human Evolution and Social Change. Gilby is also the director of the Jane Goodall Institute Research Archive and Database at ASU. 

Scientists have been debating for years whether hunting in chimpanzees involves any real coordination between hunters or whether each individual simply chases their own prey independently. This new research shows that hunts featuring the occurrence of specific hunting calls play out very differently from hunts where this signal is not produced.

“Strikingly, following the production of hunting barks, we observed more hunters joining, greater speed in beginning the chase and a shorter time to make the first capture,” says study author Zarin Machanda of Tufts University, who heads up the Kanyawara Chimpanzee Project.

“Chimps who produce hunting barks inform those nearby about their motivation to hunt, and this information may persuade reluctant individuals to join, boosting the overall chances of success,” said Joseph Mine, a PhD student at the University of Zurich who led the study.

“However,” cautions Gilby, who is an expert on chimpanzee hunting behavior, “purely observational studies like these can only give us hints about what is happening in the minds of these apes. Rather than serving to coordinate a complex, cooperative act, these barks may simply advertise that a particular chimpanzee has decided to hunt, which in turn, increases the potential success rate of other hunters, even if they don’t actively work together.

"The more hunters there are, the greater the likelihood that hunters acting in their own self-interest will make a kill.”

Co-evolution of communication and cooperation

The evolutionary biologists considered a wide array of other factors that may affect the outcome of a hunt, including the presence of skilled hunters or potential distractions, but the occurrence of hunting barks retained a key role.

“We can see from the multitude of hunting events that sometimes the chimps are just not interested in hunting as a team. But when they are especially motivated, they communicate with their group members and engage in the hunt collectively,” says Simon Townsend, a researcher at the University of Zurich who helped lead the study.

The findings offer new insights into the evolution of the amazingly complex form of communication that we see in humans today: language. It is widely accepted that communication and cooperation are tightly linked and co-evolved in humans. Over time, as one became more complex, so did the other, generating a feedback cycle that ultimately led to language. 

Evolutionary roots at least 7 million years old

However, it remains unknown how far back into humans’ evolutionary past this relationship can be traced.

The research group believes the results indicate that the relationship between vocal communication and group-level cooperation is ancient and that the link seems to have been in place for at least 7 million years — since the last common ancestor with chimpanzees.

"Vocal signals facilitate cooperative hunting by wild chimpanzees" published in Science Advances. Joseph G Mine, Katie E Slocombe, Erik P Willems, Ian C Gilby, Miranda Yu, Melissa Emery Thompson, Martin N Muller, Richard W Wrangham, Simon W Townsend, Zarin P Machanda. July 29, 2022. DOI: 10.1126/sciadv.abo5553

Julie Russ

Assistant director, Institute of Human Origins


Jane Goodall Institute chimpanzee archive coming to ASU

November 16, 2021

The physical archive of over 60 years of observations of wild chimpanzees in Gombe National Park, initiated by Jane Goodall — founder of the Jane Goodall Institute and U.N. messenger of peace — and comprising hundreds of thousands of handwritten notes by hundreds of researchers, will find a new home at Arizona State University’s newest, state-of-the-art research building, Interdisciplinary Science and Technology Building 7 (ISTB7).

The archive — the Jane Goodall Institute Gombe Research Archive — will be overseen by primatologist Ian Gilby, Institute of Human Origins research scientist and associate professor with the School of Human Evolution and Social Change. chimpanzee Gombe chimpanzee. Photo by Ian Gilby

By the late 1960s, a remote outpost in Tanzania was bustling with field assistants and students studying wild chimpanzees in Gombe National Park. This research, begun by renowned ethologist and conservationist Jane Goodall, transformed our understanding of our closest living relatives and, in turn, our own place in the world. Her early observations of chimpanzee tool use, hunting and complex social relationships revolutionized the field of primatology. Since that time, a dedicated team has collected daily handwritten data on chimpanzee life — grouping, feeding and ranging — on check sheets, as well as longhand narrative observations of behavior, including grooming, tool use, dominance and mating.

In the early 1990s, a massive effort to organize, protect and analyze data from this priceless archive was spearheaded by Gombe researcher Anne Pusey. The data was organized into a powerful relational database that has resulted in many exciting and important discoveries that build upon Goodall’s early findings and continue to be essential to a long-term understanding of chimpanzees. Gilby is the director of the Gombe Chimpanzee Database, the digital repository of the physical archive.

Following the recent retirement of Pusey, the Jane Goodall Institute forged a new partnership with the Institute of Human Origins at ASU, where the archive and database will be curated by Gilby, a 20-year researcher at Gombe, who was a graduate student of Pusey’s. Because of its scientific and historical value, this priceless resource must be properly protected and preserved, while also remaining accessible to scientists. 

“This is a dream come true,” Gilby said. “I have spent my whole career working with this amazing dataset, and I am humbled to be involved with its future, which promises many more exciting discoveries about our closest living relatives. I am particularly excited to make the data and our findings more accessible to a global audience.” 

Lilian Pintea, Jane Goodall Institute vice president of conservation science, said, “We are excited to expand our collaboration with Ian Gilby and the new partnership with IHO at ASU to help us leverage Gombe long-term data as a global asset for interdisciplinary scientific research and conservation.”

Building on the Institute of Human Origin's expertise in primatology with chimpanzee researcher Kevin Langergraber at Kibale National Park in Uganda, and Regents Professor Joan Silk’s field research studying baboons in Kenya, the relocation of the collection establishes ASU and the institute as a global hub of noninvasive research on wild primates.

The priceless Gombe Research Archive deserves world-class storage. For the continued protection of these materials, an ASU Pitchfunder campaign has been started to upgrade the storage to fire- and water-proof filing cabinets fitted with acid-free, archival-quality folders. To become a supporter of the Jane Goodall Institute Gombe Research Archive fund, donate here

Julie Russ

Assistant director, Institute of Human Origins