Validation of a non-invasive tool for monitoring adrenocortical activity in fat-tailed dunnarts (Sminthopsis crassicaudata)

Fat-tailed dunnarts are a model species in marsupial research that have been used since the 1960s, but little is known about their endocrinology. Glucocorticoids modulate several vital physiological functions, helping animals adapt to their environment. Understanding glucocorticoid biology can provide insights into a species’ fitness. Non-invasive hormone monitoring via faecal samples is a powerful tool that reduces or eliminates the need for capturing and handling animals but must be properly validated to ensure reliable results. This study aims to validate an enzyme immunoassay for monitoring faecal glucocorticoid metabolites (FGMs) in fat-tailed dunnarts. We compared the performance of four assays for monitoring adrenocortical activity in dunnarts following an open-field challenge. All four assays detected a significant increase in FGMs following the challenge, but the magnitude and consistency across individuals differed considerably. The cortisol enzyme immunoassay (AA-F) was selected as the best-performing assay to describe patterns of adrenocortical activity in the species. There was no significant difference in average FGM concentrations between males and females, although males showed a stronger response to the open-field test. Our study successfully validated an assay for the non-invasive measurement of FGMs in fat-tailed dunnarts, thereby helping understand their physiology and provide new insights for marsupial research.