de Laat, E. | Search bioRxiv

bioRxiv2025

Despotism promotes cooperation through enhanced interdependencies in non-human primate societies

The evolutionary mechanisms of cooperation are well-studied, yet what motivates individuals to cooperate remains unclear. Although conventionally associated with enhanced social tolerance (self-domestication hypothesis) and prosociality (cooperative-breeding hypothesis), individuals belonging to species that are neither self-domesticated nor cooperatively-breeding also cooperate. An overarching interdependency hypothesis posits that inter-individual dependencies promote cooperation, but comparative evidence is lacking. We experimentally studied cooperation, prosociality, and tolerance in six macaque species along a despotic-egalitarian gradient. Within-group cooperation was higher in despotic than egalitarian societies yet restricted to few partners. Prosociality, kinship, and tolerance positively predicted cooperation success. Agent-based models consistently showed that despotic societies have fewer but more stable social bonds and, thus, higher interdependencies than egalitarian ones. Our results suggest that interdependencies facilitate the emergence and maintenance of cooperation.

animal behavior and cognition↗

bioRxiv2024

Despotic long-tailed macaques benefit others in a group service paradigm

For animals living in social groups, cooperation is a key factor to success. It has been postulated that in social systems with cooperative breeding or a tolerant dominance style, individuals will benefit each other. Cooperation is, therefore, not expected in long-tailed macaques, since they do not breed together and experience a steep unidirectional hierarchy. However, previous studies have shown that they can be prosocial in a dyadic setting. This would comply with the more recently postulated dyadic interdependence hypothesis. To be able to compare their cooperative performances with other species, we set up a group service paradigm similar to that, which has been tested in a number of other species. We presented a swing set apparatus, which an actor could pull in the middle to provide a reward to another individual but without access to the reward for the actor, to three groups of socially housed long-tailed macaques. The macaques showed prosocial behaviour in the test significantly more often than in two control condition. They preferably provided to kin. The prosocial behaviour of the despotic, individual breeding long-tailed macaques counters the cooperative breeding and self-domestication hypotheses, yet supports the dyadic interdependence hypothesis, although future studies on other macaque species with more tolerant dominance styles should elucidate the effect of dominance styles on prosociality.

animal behavior and cognition↗