The Need for a Predictive, Context‐Dependent Approach to the Application of Stress Hormones in Conservation

Monitoring the impact of anthropogenic disturbance on species or populations of interest is an important goal of conservation (Van Dyke 2008). Because the effects of environmental alteration often manifest in an organism’s physiology before changes can be detected at the population level, physiological measures can provide earlier detection of disturbances and greater predictive capacity than traditional demographic methods (Wikelski & Cooke 2006; Ellis et al. 2012). This mechanistic approach, known as conservation physiology, can also help determine which populations are most susceptible to disturbance, key periods when disturbances may be most detrimental, and whether management techniques are having positive effects (Carey 2005; Wikelski & Cooke 2006). Incorporating physiological biomarkers into population monitoring also provides the opportunity to interpret anthropogenic changes from the perspective of the organism rather than the researcher and thus improve our understanding of which conditions constitute a disturbance. Glucocorticoids (GCs), often referred to as stress hormones, represent some of the most widely proposed physiological biomarkers (Cooke & O’Connor 2010). GCs (e.g., corticosterone and cortisol) act in 2 distinct and separately measurable ways as determined by their circulating concentration and the receptors to which they bind (Landys et al. 2006). GCs are best known for their role in enabling individuals to respond to unpredictable events such as extreme weather, predator interaction, or social conflict through the acute stress response (McEwen & Wingfield 2003). By increasing within minutes of