Animal welfare: What are the relationships between physiological and behavioural measures of adaptation?

Assessing the behavioural adaptation of an animal to its environment is complex, notably because numerous criteria can be taken into consideration. A better understanding of the relationships between criteria, particularly between behavioural and physiological respon-ses, might help reduce the number of parameters required to assess animal welfare. The existence of relationships between behavioural and physiological responses of animals to potentially threatening situations has been suggested both by studies comparing animals reared in different environments and by those comparing animals with extreme genotypes. Moreover, the identification of coping styles in va-rious species has strengthened the idea that physiological and behavioural responses could be related, although the precise laws governing such relationships are still difficult to establish and generalise. Thus, considering the complexity of these relationships, it appears reasonable to consider these two groups of responses as partially independent and as giving complementary information about animal welfare. In the future, the development of complex trait analyses as well as investigation at the level of the brain should improve understanding of the relationships between physiological and behavioural response