The evolution of cooperation among nonrelatives has been explained by direct, indirect, and strong reciprocity. Animals should base the decision to help others on expected future help, which they may judge from past behavior of their partner. Although many examples of cooperative behavior exist in nature where reciprocity may be involved, experimental evidence for strategies predicted by direct reciprocity models remains controversial; and indirect and strong reciprocity have been found only in humans so far. Here we show experimentally that cooperative behavior of female rats is influenced by prior receipt of help, irrespective of the identity of the partner. Rats that were trained in an instrumental cooperative task (pulling a stick in order to produce food for a partner) pulled more often for an unknown partner after they were helped than if they had not received help before. This alternative mechanism, called generalized reciprocity, requires no specific knowledge about the partner and may promote the evolution of cooperation among unfamiliar nonrelatives.

Existing global protected area networks have two shortcomings: (1) they do not cover certain habitats, and (2) local people often resent their formal management. Here, we show that communities around the world traditionally protect natural sites that are dedicated to ancestral spirits or deities. Such sites cover a wide variety of habitats and are often located in biodiversity rich regions. Case studies on sacred groves show that these small forest patches play an important role in biodiversity conservation. Furthermore, natural sacred sites are maintained through traditional methods of community based conservation that do not require governmental involvement. Incorporating these sites into conservation networks could enhance the effectiveness of protected areas by covering a wider variety of habitats and by harnessing the support of local people. In this article, we discuss current threats to sacred groves that need to be addressed through management approaches. More research on the ecology and underlying socioeconomic mechanisms of natural sacred sites is required to fully reveal their potential for biodiversity conservation.

No abstract