Review of factors influencing stress hormones in fish and wildlife

Conservation efforts to better understand how wildlife populations respond to environmental change and anthropogenic disturbance has led to a proliferation of research examining physiological indicators of stress response in wildlife. Glucocorticoid stress hormones (GCs), typically cortisol and corticosterone, are among the most frequently measured indicators of the vertebrate stress response. To review the current state of research on stress physiology of free-ranging animals and its application to conservation, we canvassed more than 1000 articles on GC measures in wildlife published since 1969. For 454 studies published since 1990, we assessed the most commonly analysed correlates and disturbances and conducted a meta-analysis on commonly studied species. We noted a prominent divide in the legacies of fish-related analyses and those of higher order vertebrates and the need and opportunity to transfer knowledge between fields. Fish studies most frequently measured physiological indicators, condition, and the relationship between stress and mortality, whereas other vertebrate studies most frequently measured reproduction, condition, and environmental correlates. Correlates that significantly influenced GC levels across all vertebrate groups and are thus important to control for in study design and analyses include density and dispersal of conspecifics, season, reproductive status, and social status. Consistent trends across commonly studied species included positive GC response to capture and handling, reduced GC response related to acclimation, and a lack of correlation between condition and baseline GC levels. Our synthesis within and across diverse taxonomic orders reveals substantial research coverage but a lack of depth in multivariate analyses and a disparity in how correlates are controlled. This paper provides a comprehensive assessment of correlates and disturbances that influence GC measures and, as such, has useful applications to assist conservation physiologists in study design, analysis, and interpretation. (C) 2013 Elsevier GmbH. All rights reserved.