Noninvasive Assessment of Stress and Reproduction in Captive Lions (Panthera leo) Using Fecal Hormone Analysis

Assessing steroid hormones through feces provides invaluable insight on the stress and reproductive physiology of wildlife, and has been broadly applied to monitor the health and welfare of wild animals managed under human care. This study utilized fecal hormone monitoring to evaluate adrenal and gonadal activity in 18 captive lions (Panthera leo) across five Spanish zoological institutions, focusing on how biological and management factors affect these metrics. We analyzed fecal glucocorticoid metabolites (FGM) concentrations and, additionally in females, fecal progesterone (FPM), estradiol (FEM), and androgen (FAM) metabolites in relation to their reproductive status. Results indicated significant variability in FGM levels among individuals, with no consistent trends influenced by sex or zoo environment, including changes in the frequency of providing environmental enrichment at two zoos. Importantly, reproductive status significantly impacted adrenal and gonadal hormone levels; ovariectomized lionesses showed lower concentrations of FGM, FPM, and FEM compared to intact and deslorelin-implanted females, the latter of which exhibited higher and more variable FAM levels. These findings advance our understanding of hormone patterns in lions and suggest implications for their management in captivity.