Science-based assessment of animal welfare: wild and captive animals.

Science-based assessment of animal welfare in wild and captive animals has, during the past ten years, benefited from increased interest in and research into consciousness, emotions, stress and pain. Because it is impossible to make a detailed physiological study in free-living animals, reliance must be placed on behaviour and Darwinian fitness, which have been shown to correlate to welfare. Only in captive animals can more detailed physiological studies be made, and then not without difficulty. In short, the welfare of an animal is shown to be compromised if the animal exhibits similar behaviour to that of animals whose physiological responses have been confirmed as indicating poor welfare, and if its Darwinian fitness is compromised in similar ways to such animals.