NON-INVASIVE MEASURES OF STRESS IN AUSTRALIAN MAMMALS

As traditional sampling techniques can elicit a stress response and confound measurements, the development of non-invasive or minimally invasive approaches for monitoring stress physiology has gained considerable attention.

Although there are obvious advantages to non-invasive hormone monitoring, proper validation is critical (Sheriff et al. 2011; Fanson et al. 2017). Circulating GCs are metabolised into a diverse array of molecules by liver and gut bacteria before excretion (Touma and Palme 2005). Therefore, it is necessary to biologically validate an assay by demonstrating that it accurately reflects changes in adrenal activity. This is typically achieved by stimulating adrenocortical GC production pharmacologically (adren­ocorticotropic hormone [ACTH] injection) or biologi­cally (stressful event) and monitoring changes in excreted GC metabolites immediately before and after this event (Touma and Palme 2005; Sheriff et al. 2011). Steroid metabolism can vary across species and even among sexes, so assays must be validated for each species and, ideally, each sex (Touma and Palme 2005). It is also important to note that the antibodies produced by differ­ent manufacturers may have different binding properties, even if the antibodies are raised against the same ligand (e.g. corticosterone), so each specific antibody needs to be validated (Fanson et al. 2017).

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