Vol. 10, Issue 11, Part G (2025)

Author(s): Ravinder, Aditya Mishra, Pragati Patel, Anil Gattani, Anand Kumar Jain, Sanju Mandal, Akansha Singh and Purnima Singh

Abstract: The captive environment can be a significant source of stress for large felids, potentially disrupting endocrine function. While glucocorticoids are well-established stress indicators, the relationship between captivity-induced stress and thyroid hormone metabolism in tigers is poorly understood. This study aimed to quantify the effects of specific captive environmental and biological factors on faecal concentrations of cortisol, triiodothyronine (T3) and thyroxine (T4) in tigers. Faecal samples were collected non-invasively from 44 tigers across four zoological facilities in Madhya Pradesh, India. Concentrations of cortisol, T3, and T4 metabolites were determined using validated enzyme-linked immunosorbent assays (ELISA). Environmental variables (enclosure size, enrichment, water body size, keeper presence) and biological variables (origin, sex, age) were recorded for correlation with hormonal data. Tigers housed in small enclosures with low environmental enrichment exhibited significantly higher concentrations of faecal cortisol (140.13 ± 6.90 ng/ml), T3 (11.66 ± 3.16 ng/ml) and T4 (40.42 ± 10.95 ng/ml) compared to tigers in large, highly enriched enclosures (cortisol: 89.47 ± 5.89 ng/ml; T3: 7.43 ± 0.63 ng/ml; T4: 25.77 ± 2.19 ng/ml). Zoo-born tigers had higher cortisol and T3 levels than wild-born conspecifics. A significant positive correlation was found between cortisol and stereotypic behavior. T3 and T4 levels showed a strong positive correlation with cortisol levels across all stress-associated conditions. Sub-optimal captive conditions, particularly spatial restriction and lack of enrichment, are associated with a concurrent elevation of faecal cortisol, T3 and T4. This suggests a synergistic endocrine response where stress may drive an increase in metabolic rate. Our findings underscore the critical importance of providing large, naturally enriched enclosures to maintain physiological homeostasis in captive tigers.

DOI: 10.22271/veterinary.2025.v10.i11g.2762