Cortisol as a Stress Indicator of Environmental Change in Captive Cynomolgus Macaques (Macaca fascicularis)

Relocation and social separation are routine yet potent stressors in captive primate management. Although acclimation is central to welfare, assessing physiological recovery in untrained animals poses a fundamental challenge: invasive sampling can confound the stress response it aims to measure. Moreover, stress responses unfold differently across biological matrices, and these matrix-specific acclimation patterns have rarely been concurrently characterized in experimentally naïve animals. We examined stress adaptation over 8 days in eight untrained cynomolgus macaques ( Macaca fascicularis ) transferred from group to single housing, comparing glucocorticoid dynamics across plasma and saliva (Days 0, 4, 8), urine and feces (daily), and hair (on Day 0). We also measured locomotor activity (Days 1, 3, 5, 7), as well as daily food intake and fluid consumption. Cortisol concentrations peaked on the relocation day and generally declined over 8 days with matrix-specific kinetics. Plasma and salivary cortisol showed monotonic declines. Urinary cortisol metabolites declined overall, interrupted by a transient elevation on Day 4, when we anesthetised the macaques to sample plasma and saliva. Fecal metabolites showed no clear recovery pattern. Fluid intake and activity increased progressively, indicating behavioral acclimation. Hair cortisol was positively associated with endpoint plasma and urinary cortisol, suggesting chronic HPA tone may influence recovery trajectory rather than initial stress reactivity. Overall, multiple endocrine and behavioral parameters began to stabilize within 8 days, with substantial interindividual variation. Urinary cortisol metabolites, triangulated with daily hydration and activity records, offered an optimal balance of feasibility and sensitivity for short-term welfare monitoring in untrained, singly housed macaques. Hair cortisol may help to identify individuals susceptible sustained stress responses. Ultimately, integrating these matrices can support refinement of husbandry practices and targeted interventions to safeguard primate welfare.