High ranking chimps act as mediators

Conflict management is highly significant for life in social groups, the researchers concluded in their findings published in the magazine PLoS ONE. The study was based on the behaviour of a group of hominids in the zoo at Gossau in Switzerland.

The team said it was astonishing that chimpanzees were able to mediate in a conflict, without themselves deriving any immediate advantage from their efforts.

“The rarest and most interesting form of conflict management is policing, that is impartial interventions by bystanders, which is of considerable interest due to its potentially moral nature,” they said.

The team led by anthropologists Carel van Schaik and Claudia Rudolf von Rohr observed a group of 11 chimpanzees (Pan troglodytes), evaluating their natural behaviour without provoking conflict. The group consisted of two adult and one young male, as well as six adult and two young females.

Three of the adult females had joined the group recently. Soon after the study began, three additional females were introduced. At the same time there was conflict over ranking order among the two adult males. These factors combined to cause instability in the group and provided considerable grounds for disagreement.

Data collected between February 2007 and November 2008 was then compared with that from studies conducted on chimpanzee groups in zoos in Basel, Chester in Britain and Arnheim in the Netherlands.

The conflicts centred on competition among the females for food and among the males for access to the females. The researchers counted 438 conflict situations in their observation of the Gossau group. Impartial mediators intervened in 69 cases.

In all cases, one of the two senior males was the mediator.

Often merely approaching the squabbling parties was sufficient, although in some cases making a clear threat or placing himself between them was required. As many as 60 of these interventions proved successful.

There were similar results from the Chester and Arnheim studies, although senior females were also involved in mediation there.

The researchers noted that mediation was not without its risks to the mediator, as he or she tended to draw the aggression of the fighting parties. This could be the reason that animals high up in the hierarchy were always involved.

There is a clear evolutionary advantage from the mediation, as greater stability within the group furthers the survival of all its members. “These results suggest that the primary function of policing is to increase group stability. It may thus reflect pro-social behaviour based upon community concern,” the team wrote.