Research with chimpanzees shows that cooperation and leadership shape sustainable use of resources in our closest living relatives
A group of four chimpanzees surround a bowl of yoghurt, with one player sitting out. A single stick remains, supporting the lid and stopping it from closing over the delicacy.
© Kirsten Sutherland et al. (Communications Psychology, 2026)
To the Point
- Resource use: Chimpanzee groups achieve sustainable resource use in a social dilemma.
- Unexpected group size effect: Groups of four chimpanzees retained access to a shared resource for significantly longer than pairs did.
- Social tolerance matters: Groups with low levels of aggression and high levels of social tolerance were the most successful at sustaining the resource.
- Role of dominance: Cooperation was strongest when the highest-ranking chimpanzee showed restraint, emphasising the importance of tolerant leadership.
Despite being one of the most cooperative species on the planet, humans routinely fail to manage shared resources sustainably. We overfish from the oceans, burn fossil fuels, and over-prescribe antibiotics; behaviours that offer individualistic short-term benefits, but result in long-term collective negative outcomes. Studying our closest living relatives, the non-human great apes, can help us understand how human cooperation has evolved, and under which conditions cooperative sustainability tends to succeed and fail.
In a new study, researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, address this issue by presenting chimpanzees with a controlled 'resource dilemma' that reflects the conflict between personal gain and collective sustainability.
A resource dilemma for chimpanzees
The chimpanzees encountered a pool of yoghurt, a desirable treat, which they could access by dipping sticks into. However, the sticks also supported a lid which, if left unsupported, would slowly close over the resource. Therefore, at least one stick had to remain inside the pool to keep it accessible. If the lid was left to fully close, it could not be reopened. "There was a clear conflict between feeding individually and keeping the resource available for the group," explains first author Kirsten Sutherland. "To sustain access, at least one chimpanzee had to temporarily forgo eating."
As there were always as many sticks as there were chimpanzees, not all individuals could feed at the same time if the group wanted to keep the yoghurt accessible. To examine the effect of group size, the researchers tested the chimpanzees either in pairs or in groups of four. In total, 24 groups took part, each completing 18 test trials and 18 control trials. In the control condition there was no lid, and therefore no dilemma, allowing the researchers to measure how quickly the sticks would be removed under normal conditions.
Larger groups cooperate more effectively
Contrary to expectations based on research into human cooperation, the pairs did not solve the dilemma well. They behaved similarly in the test and control conditions, usually removing all the sticks quickly and making the yoghurt inaccessible.
The groups of four, in contrast, showed a clear pattern of leaving one stick in the pool for on average of 83 seconds longer if removing the stick would make the yoghurt inaccessible. "The same chimpanzees that failed to overcome the dilemma in pairs showed greater sensitivity when placed in a larger group," says Sutherland. "They modified their behaviour in a way that benefited the group as a whole."
Social tolerance and leadership drive success
Cooperation was most successful in groups with high social tolerance - groups whose members typically spent time in close proximity with low levels of aggression. The researchers also found that the resource remained accessible for longer when it was the highest-ranked chimpanzee that was left without a stick. "This shows that dominance does not necessarily undermine cooperation," says senior author Daniel Haun. "What matters is how dominant individuals use their position. When high-ranking chimpanzees exercised restraint, the whole group benefited."
However, when dominant individuals took more than their fair share - something that chimpanzees have the power to do because of their strong social hierarchies - collective sustainability was more likely to fail.
Broader implications
These findings contribute to the growing body of research on dominance, social tolerance and prosocial behaviour in chimpanzees: This study indicates how chimpanzee groups can manage resources sustainably and benefit from the presence of a tolerant and non-competitive dominant.
The results also have implications for study design of non-human primate cooperation tasks. Many social cognition experiments test apes in pairs, however the new findings suggest that researchers could be setting their participants up for failure. "Chimpanzees are adapted for group living," notes Haun. "If we want to understand their cooperative abilities, we need to study them in social contexts that reflect that reality."
This study clearly demonstrates that sustainable cooperation among chimpanzees hinges not only on group size, but also on social tolerance and the behaviour of individuals in positions of power - parallels that may also be relevant to human societies.
