Non-invasive assessment of adrenocortical function as a measure of stress in the endangered golden langur.

The golden langur (Trachypithecus geei) is an endangered primate endemic to northern India and Bhutan. The main stressors to the species are habitat degradation and fragmentation. Non-invasive fecal glucocorticoid metabolite (fGCM) analysis is a powerful tool for assessing stress associated with environmental disturbances in wildlife. However, interspecific differences in glucocorticoid metabolism require careful selection of the antibody used in their quantification. The goals of this study were to: 1) validate an enzyme immunoassay (EIA) to determine fecal GC metabolite (fGCM) concentrations in the golden langur and 2) compare fGCM concentrations between golden langurs living under different environmental conditions. We compared five enzyme immunoassays for determining stress related physiological responses in golden langurs by performing an adrenocorticotropic stimulation test in both sexes. Our validations identified an 11-oxoaetiocholanolone EIA detecting 11, 17 dioxoandrostanes as the most suitable assay for monitoring adrenocortical activity in the species. FGCM concentrations from semi-captive temple langurs were significantly higher than respective stress steroid concentrations in free-ranging or pet/zoo langurs. This study presents a validated practical method for non-invasive monitoring of adrenocortical function in this rare and declining species.