of situations it responds to as stressful and on the nature of its response (Newton and Levine, 1968). Age, sex, and seasonal variations are other factors known to affect the intensity of stress and distress and the situations that elicit these reactions.
Most research thus far has been oriented toward theoretical issues, and this work needs to continue. But future research must explicitly include concern with identifying the actual conditions in the captive environment that are sources of stress and distress and the steps that can be taken to prevent or alleviate the conditions. That concern should be clearly reflected in research designs.
The aim of experiments on stress and distress in captive environments is not to create a facsimile of the natural habitat in appearance or function, but to identify aspects of captive environments that impinge most directly on processes related to stress and distress and to determine how they do so. For example, one might expect a species that was solitary, timid, and heavily preyed on in its natural environment to react more intensely to the close presence of conspecifics, to handling and other routine caretaking procedures, and to being placed in novel settings than a species that was highly social, bold, and predatory. That is a testable possibility.
It is equally important that the effectiveness of various living arrangements and techniques in alleviating stress and distress be investigated experimentally (see Chapters 4 and 5). Realistic recommendations based on experimental findings will need to consider economic and other practical concerns, in addition to matters related strictly to animal well-being. Although objective assessments of the sources and alleviation of stress and distress in captive animals constitute an ambitious and expensive program, it is clearly feasible and well within the capabilities of contemporary scientific methods.
Ideally, the scientific investigation of stress and distress would be based on explicit and universally agreed-on definitions of these conditions. But such a connection has proved elusive. It is hoped that the definitions and concepts of stress and distress formulated in this report will take the terms one step closer to being readily useful in describing clinical signs.
Physiologic assessments of stress have been carried out for a number of years, and a considerable amount of information is available on (often weak) interrelations between various measures and their functional significance. However, we need much more information on the interrelations between behavioral, physiologic, biochemical, reproductive, and clinical signs of stress. The association between behavioral and physiologic measures is not always strong, and in some cases these measures might not even be associated (e.g., Weinberg and Levine, 1980).
The importance of firm baseline data (norms) is recognized; the conditions that contribute to departures from baseline values and the implications of such departures for physical health, reproduction, and vitality have been explored for some species in reasonable detail and are the objects of current research. That does not imply that stress research is in a mature state, particularly as it is related to matters of well-being, but knowledge and theoretical issues regarding stress are more completely developed than those regarding distress.