Predation enhances cooperation in wee little birds.
In a recent article entitled "The increased risk of predation enhances cooperation"published in Proceedings of the Royal Society B, Volume 277, Pages 513 – 518 and available here, Indrikis Krams and colleagues experimentally demonstrate an interaction between predation risk and cooperation in breeding songbirds. It is worth reading in the light of current discussions about the co-evolution of warfare and cooperation (for example: Bowles, 2008).
Abstract: Theory predicts that animals in adverse conditions can decrease individual risks and increase long-term beneﬁts by cooperating with neighbours. However, some empirical studies suggest that animals often focus on short-term beneﬁts, which can reduce the likelihood that they will cooperate with others. In this experimental study, we tested between these two alternatives by evaluating whether increased predation risk (as a correlate of environmental adversity) enhances or diminishes the occurrence of cooperation in mobbing, a common anti-predator behaviour, among breeding pied ﬂycatchers Ficedula hypoleuca. We tested whether birds would join their mobbing neighbours more often and harass a stuffed predator placed near their neighbours' nests more intensely in areas with a higher perceived risk of predation. Our results show that birds attended mobs initiated by their neighbours more often, approached the stuffed predator signiﬁcantly more closely, and mobbed it at a higher intensity in areas where the perceived risk of predation was experimentally increased. In such high-risk areas, birds also were more often involved in between-pair cooperation. This study demonstrates the positive impact of predation risk on cooperation in breeding songbirds, which might help in explaining the emergence and evolution of cooperation.