Chimpanzee cooperators

Chimpanzees recognized when collaboration was necessary and chose the best collaborative partner

March 02, 2006

In the animal kingdom cooperation is crucial for survival. Predators hunt in prides and prey band together to protect themselves. Yet no other creature cooperates as successfully as we do. But where did this ability come from, and is it uniquely human? In a new study to be published in Science on 3 March 2006, Alicia Melis and co-authors from the Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany show that our close relatives, chimpanzees, are much better cooperators than we thought.

‘We’ve never seen this level of understanding during cooperation in any other animals except humans,’ says Melis. Cooperation happens all the time in the animal kingdom. A pride of lions cooperates to hunt down a gazelle. A herd of elephants band together to protect themselves from predators. But there may not be much thinking going on behind this kind of cooperation. It could be that by each animal wanting the same thing and working at the same time, success happens by accident.

In Melis’ study which took place at Ngamba Island Chimpanzee Sanctuary in Uganda, not only did chimpanzees understand when they needed help, they understood their role, their partner’s role, and chose who they wanted to work with.

To reach a food tray, the chimpanzees had to pull two ends of a rope which dragged the tray towards them. Both rope ends had to be pulled at the same time or the rope was simply pulled out. Melis found that the chimpanzees only let a partner into the room (by opening their door) when the rope ends were too far apart to pull them on their own.

‘Not only did they need to know when they needed help, they had to go out and get it.’ Melis says. ‘Then they had to wait until their partner came in and pull on the rope at the same time. The chimps really had to understand why they needed their partner.’

Just like people, there were better cooperators than others. Mawa, the dominant chimpanzee, was not a very good cooperator. He didn’t wait for his partner and often pulled the rope from the tray. Bwambale, on the other hand, was a great cooperator. He always waited for his partner and was nearly always successful in getting the food. At first, the chimpanzees chose Mawa and Bwambale equally, but when the chimpanzees learned what a hopeless cooperator Mawa was, most chose Bwambale on the next trial.

Melis was excited by the results. ‘This is the first study that lets chimps choose who they want to cooperate with. We found that chimps choose a partner based on their effectiveness. Clearly, chimps can remember who’s a good and who’s a bad collaborator. Bad collaborators suffer by not being chosen next time.’

This complexity of cooperation means that humans and chimpanzees might have inherited our cooperative abilities from our common ancestor 6 million years ago. However, Melis is quick to draw the line between chimpanzee and human cooperation.

‘There is still no evidence that chimpanzees communicate with each other about a common goal like children do from a very early age. There’s also no evidence that chimpanzees can learn how good a partner is by watching them interact with others. It just suggests that when chimpanzees cooperate they understand a bit more than we thought. Hopefully, future studies can show us what it is that makes human cooperation so unique.’

Melis’ studies are among the first to be done in a chimpanzee sanctuary in Africa. ‘Sanctuaries are doing an incredible job saving chimps whose families were killed by the bush-meat trade. They also provide a wonderful service to us and the research community. Hopefully, as these and similar results become more widely known, it will raise awareness that these are intelligent animals who deserve respect and protection.’

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