Fecal cortisol metabolites (FCMs) are increasingly used to index physiological stress in wildlife. Cortisol and other glucocorticoids (GCs) act to mobilize glucose, providing immediate energy to respond to environmental perturbations. Cortisol, the predominant GC in most mammals, is metabolized by the liver and excreted as FCMs in feces. However, for FCMs to serve as a meaningful physiological index, we must understand the link between circulating stress hormone levels in the blood that impact host physiology and expression of measurable fecal hormone metabolites. Thus, my goal is to quantify the link between blood cortisol and FCM concentration. To achieve my goal, I collaborated with scientists at Washington State University Bear Research Center to validate the use of FCMs as a potential noninvasive metric to index stress in brown bears (Ursus arctos). As such, nine unanesthetized captive brown bears were injected with synthetic adrenocorticotropic hormone (ACTH) at 5μg/kg intravenously and 10mL of blood was drawn at 0h, 3h, 6h, 24, 48, and 72h post-injection to measure changes in blood cortisol concentrations. Fecal samples were collected continuously from 24h pre-ACTH challenge through 72h post-ACTH challenge. While blood cortisol values peaked around 6-hours post-injection, peak concentration of FCMs occurred around 24 hours post-injection, suggesting lag time between secretion of cortisol following a stressful event and expression of FCM is ~24 hours in brown bears. My work will provide a quantitative link between blood cortisol and expression of FCMs in brown bears, which is critical for indexing physiological stress in captive and free-ranging brown bears.
Faculty Advisor Email
Pinero, Justin A. and Lafferty, Diana JR, "Plasma and fecal cortisol metabolite concentrations following an ACTH challenge in captive brown bears (Ursus arctos)." (2022). Celebration of Student Scholarship. 39.