# Chimpanzee groups achieve sustainable resource use in a common-pool resource dilemma

## TL;DR

Chimpanzee groups of four managed a shared food resource better than pairs, with social tolerance helping them avoid overuse.

## Contribution

The study introduces a novel experimental paradigm to investigate chimpanzee resource management in social dilemmas.

## Key findings

- Quartets maintained the resource longer than dyads.
- Social tolerance was positively linked to quartet success.
- Dominant apes with lower payoffs contributed to quartet success.

## Abstract

Common-pool resource dilemmas are group resource sustainability problems that are sensitive to over-extraction. While human strategies for overcoming common-pool resource dilemmas are well studied, the comparative evolutionary perspective has received little attention. Here, we compare resource management of chimpanzees (N = 15) grouped as dyads and quartets using an original experimental paradigm. The participants could use sticks to feed from a pool of yoghurt. The number of sticks equalled the number of players, and removing all of the sticks triggered resource collapse, thereby creating a social dilemma. Quartets were found to maintain the resource longer than dyads. Quartets’, but not dyads’, success was positively associated with social tolerance. Furthermore, quartets were more successful when the dominant ape acquired the relative lowest payoff. These results suggest that chimpanzees respond differently to cooperative sustainability problems depending on group size, with social tolerance playing an important role. The findings have implications for studying the evolution and diversity of hominid cooperation, in particular, highlighting that group size should be carefully considered in the design of non-human primate cooperation experiments.

Groups of two or four chimpanzees encountered a collective resource sustainability problem. Quartets avoided resource collapse for longer than dyads, with group social tolerance playing a supportive role.