Biology of Stress


The concept of stress is notoriously difficult to define, despite its ubiquity in both common parlance and the scientific literature. Given the clear importance of understanding how organisms deal with challenging environments in both natural and husbandry contexts, examining the relationships between internal and external stressors and the stress response is essential to working with both captive and wild animals of any species of any class. In this chapter, we outline historical and contemporary concepts of stress, with an emphasis on how these ideas can inform our approaches to caring for reptiles in captive contexts and decision-making in a management context. We include a description of the physiological stress response systems, with examples of studies that have improved our understandings of the mechanisms and indicators of the stress response in reptiles. Furthermore, we demonstrate how the stress response is manifest in other aspects of organismal function, including behaviour, social interactions, reproduction, and immunity. Identifying bioindicators of stress and how best to mitigate or manage them is central to good husbandry practice.

Given the influence of the stress response at every level of organisation, good husbandry must also be regarded as essential to good research. It should also be clear that, within limits, the stress response is a normal aspect of the functioning of healthy individuals and that clinically conspicuous pathology emerges only when stressors are repeated, sustained, or extreme. Finally, we describe new findings and new directions that may provide useful data and techniques to facilitate the identification of stressors and the mitigation of negative effects. Throughout this chapter, we emphasise the need to examine stress in reptiles from a reptilian point of view, adopting an ethological approach to see the world from the organisms’ perspective. Of course, we will never know what it is like to be a reptile. Given the vastly different physiological needs and sensory systems of reptiles compared to humans, and the great variation among reptilian taxa, our best approximation of the reptile’s experience necessitates the use of data-driven decisions based on empirical research. To inform a continuing improvement of captive reptile care, we summarise recent work on the theoretical understanding of stress and the application of that understanding in practice.


  • Adaptive scope
  • Allostasis
  • Behaviour
  • Captive care
  • Catecholamines
  • Glucocorticoids
  • Homeostasis
  • Hypothalamic–pituitary–adrenal axis
  • Physiology
  • Reptile
  • Stress
  • Stress response
  • Sympathetic adrenomedullary axis
  • Welfare