Fecal Glucocorticoid and Androgen Metabolites in Eastern Gray Kangaroos (Macropus giganteus) Following Environmental...

Zoo animals often undergo changes in housing to improve management and social conditions, but these shifts may initially act as stressors, disrupting homeostasis. The hypothalamic-pituitary-adrenal (HPA) axis is activated in response, releasing several hormones. While adaptive in the short term, prolonged HPA activation may affect welfare. This study monitored HPA activity in eastern gray kangaroos (Macropus giganteus) following relocation by measuring fecal glucocorticoid metabolites (GCMs), androgen metabolites (AMs), and their ratio. Three kangaroos (two females, one male) were transferred from Parco Natura Viva to Parco Zoo Falconara (Italy). Fecal samples were collected daily for 10 days postarrival, then weekly from January 20 to April 9, 2024. GCMs and AMs were analyzed using enzyme immunoassays. Descriptive statistics and Spearman coefficient (ρ) were used. GCM levels (14-262 ng/g) rose initially (> 100 ng/g), declined, and stabilized by day 10, with another rise observed in mid-March. AMs also declined after the first days (from 34 ± 21.5 in the first week to 9 ± 3.6 ng/g over the following 40 days), with the male showing a distinct mid-March increase. GCM and AM levels were positively correlated (ρ = 0.741, p < 0.001). The GCM/AM ratio exceeded five initially in all subjects, dropping quickly, but exhibited a variable pattern in females. Results suggest a rapid physiological adaptation to the new environment, with later elevations tied to new stressors or seasonality. Given overlapping steroid pathways, AM interpretation requires caution. GCM and AM monitoring can serve as valuable noninvasive tools for welfare assessment, but accounting for seasonal variation in both sexes and integrating behavioral observations is essential.