Glucocorticoids and wildlife health: Evaluating the stress of translocation and chronic contaminant exposure.

摘要

All vertebrates respond to noxious stimuli or stressors by evoking the stress response, a suite of behavioral and physiological responses necessary for coping with adverse environmental conditions. Inappropriate initiation or maintenance of the stress response can have multiple negative effects on health and fitness. Therefore, a measurable indicator of the stress response can supply important information about the health of animals. The hypothalamic-pituitary-adrenal or interrenal axis is one of the primary systems activated during the stress response, resulting in the release of steroid stress hormones, called glucocorticoids (GCs, e.g. corticosterone in birds). Determination of GC concentrations allows for analysis of relative stress levels between individual animals and groups of animals exposed to different environmental conditions.; The research presented here addresses the potential utility of GCs as an indicator of wildlife health through investigation of two promising conservation applications, endangered species translocation and chronic contaminant exposure. We measured and monitored fecal GCs in Grevy's zebra (Equus grevyi ) during translocation, from the time of capture through the months following release. GCs were notably elevated during their time in captivity and gradually decreased back to baseline after release, suggesting acclimation to the new environment. The results support the usefulness of GC measurement for assessing the stress of translocation, reintroduction and rehabilitation.; To investigate the impact of pollution on GCs, we looked at two high trophic level avian species frequently used as wildlife indicators of contaminant exposure, the insectivorous tree swallow (Tachycineta bicolor) and piscivorous common loon (Gavia immer). We measured corticosterone concentrations in tree swallows from sites with different levels of contamination with polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). We also compared corticosterone concentrations with mercury (Donnelly et al.) levels in tree swallows and loons. The results did not reveal a consistent or predictable pattern but the combined findings strongly suggest that tree swallows and loons chronically exposed to contaminants exhibit altered baseline and stress-induced corticosterone responses.; Taken as a whole, the research presented in this thesis supports further use and investigation of GCs as a tool for assessing and monitoring wildlife health in a wide range of conservation and environmental studies.