Cortisol measurement in Koala (Phascolartos Cinereus) fur

Optimal methods of hormone extraction used to measure stress in animals across sample types are not always the same. Australia's iconic marsupial species, the koala (Phascolarctos cinereus), faces prolonged exposure to anthropogenic-induced stressors and assessment of chronic stress in wild populations is urgently warranted. One of the most effective ways to measure chronic stress is through analyzing the glucocorticoid hormone cortisol in hair or fur, as it supports physiological and behavioral responses. This laboratory validation study aims to test current techniques to validate an optimal hormone extraction method to be used as a non-invasive measure of cortisol in koala fur. It is recognized that using non-invasive techniques to measure stress hormones is preferred over traditional, invasive techniques due to their ideal practical and ethical standpoints. Additionally, it is comparatively easier to acquire fur from koalas than it is to acquire samples of their blood. This study used samples of koala fur acquired from the Adelaide Koala and Wildlife Hospital to run a number of hormone extraction techniques in an attempt to validate an optimal cortisol extraction method. Results showed that 100% methanol provided the most optimal solvent extraction compared to 100% ethanol or 100% isopropanol based on parallelism results. In conclusion, this method of cortisol extraction from koala fur provided a reliable non-invasive assay that could be used to study chronic stress in koalas.