Leptin and social environment influence the risk-taking and feeding behaviour of Asian blue quail

Optimality models predict that hungry animals should be more willing to take risks than satiated individuals; thus, the decision whether to forage is influenced by the physiological process mediating the sensing of energy reserves. An important substance involved in this sensing process is leptin, a protein hormone known to down-regulate appetite and increase energy expenditure. However, feeding and risk-taking behaviours are also influenced by the behaviour of surrounding individuals. By increasing leptin levels in a focal bird and/or in its groupmates, we studied the combined effects of physiological and social factors on the risk-taking and feeding behaviour of Asian blue quail, Coturnix chinensis. Risk-taking behaviour, estimated by the time taken to start feeding, was dependent on social factors and a birdʹs own weight but not on whether it was treated with leptin; focal birds with leptin-treated companions took longer before feeding than did focal birds with control companions. Total feeding time, on the other hand, was physiologically governed with no effect of the companions; leptin-treated focal birds spent less time feeding than did control focal birds. To our knowledge, this study is the first to investigate the interaction between leptin and social factors in animal behaviour.