Journal of Comparative Physiology B

, Volume 182, Issue 7, pp 861–879 | Cite as

Interpreting indices of physiological stress in free-living vertebrates

  • Christopher P. Johnstone
  • Richard D. Reina
  • Alan Lill
Review

Abstract

When vertebrate physiological ecologists use the terms ‘stress’ or ‘physiological stress’, they typically mean the level of hypothalamus–pituitary–adrenal (HPA-) axis activation. Measurements of stress hormone concentrations (e.g. glucocorticoids in blood, urine or faeces), leukocytes (e.g. the neutrophil–lymphocyte ratio or heterophil equivalent), immunofunction (e.g. innate, cell-mediated or humoral immunity measures) and regenerative anaemia (e.g. mean erythrocyte volume and red blood cell distribution width) have all been used to estimate HPA-axis activity in free-living vertebrates. Stress metrics have provided insights into aspects of autecology or population regulation that could not have been easily obtained using other indices of population wellbeing, such as body condition or relative abundance. However, short- and long-term stress (often problematically termed acute and chronic stress, respectively) can interact in unpredictable ways. When animals experience trapping and handling stress before blood, faeces and/or urine is sampled, the interaction of short- and long-term stress can confound interpretation of the data, a fact not always acknowledged in studies of stress in free-living vertebrates. This review examines how stress metrics can be confounded when estimates of HPA-axis activation are collected for free-living vertebrates and outlines some approaches that can be used to help circumvent the influence of potentially confounding factors.

Keywords

HPA axis Corticosteroids Corticosterone Cortisol Glucocorticoids H:L ratio N:L ratio Physiological stress Stress/heat shock proteins Vertebrate 

Notes

Acknowledgments

We would like to thank all those who provided feedback on the ideas presented here at the ANZSCPB conference in Tasmania, 2011. We would also like to thank the four anonymous reviewers, whose comments have helped improve the manuscript.

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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • Christopher P. Johnstone
    • 1
  • Richard D. Reina
    • 1
  • Alan Lill
    • 1
  1. 1.School of Biological SciencesMonash UniversityMelbourneAustralia

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