Baseline,diurnal variations,and stress-induced changes of stress hormones in three captive beluga whales,Delphinapterus leucas

Concentrations of plasma adrenocorticotropic hormone (ACTH), cortisol, and aldosterone were investigated in three adult beluga whales (Delphinapterus leucas), held in a large outdoor public aquarium exhibit. The purpose of this study was to evaluate resting concentrations of these hormones and associated diurnal variations with routine interactions and medical procedures. Resting blood samples were collected voluntarily from the ventral fluke veins at predetermined times of the day to evaluate diurnal changes in analyte concentrations. In addition, hematology and serum chemistry analyses were performed to monitor health status and evaluate changes related to physical exam procedures. Analogous sampling was conducted during out-of-water physical examinations and before and after wading-contact sessions (WCS). Baseline stress hormone concentrations (± SD) were as follows: plasma ACTH (8.41 ± 5.8 pg/mL), serum cortisol (1.80 ± 0.71 g/dL), and serum aldosterone (11.42 ± 5.5 pg/mL). Plasma ACTH and cortisol concentrations were consistently higher in early morning than evening, while aldosterone was higher in the evening. All stress-related hormones were significantly elevated during physical examination. Plasma ACTH concentrations were most increased, 5–10-fold, during physical examination, whereas cortisol and aldosterone showed 2–4-fold elevations. Stress response analytes measured during the WCS did not differ significantly from baseline concentrations.