Testosterone and progesterone concentrations in blow samples are biologically relevant in belugas (Delphinapterus leucas)

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Steroid hormone analysis in blow (respiratory vapor) may provide a minimally invasive way to assess the reproductive status of wild cetaceans. Biological validation of the method is needed to allow for the interpretation of hormone measurements in blow samples. Utilizing samples collected from trained belugas (Delphinapterus leucas, n = 20), enzyme immunoassays for testosterone and progesterone were validated for use with beluga blow samples. Testosterone concentrations in 40 matched blood and blow samples collected from 4 male belugas demonstrated a positive correlation (R2 = 0.52, p < 0.0001). Progesterone concentrations in 64 matching blood and blow samples from 11 females were also positively correlated (R2 = 0.60, p < 0.0001). Testosterone concentrations (mean ± SD) in blow samples collected from adult males (119.3 ± 14.2 pg/ml) were higher (p < 0.01) than that of a juvenile male (<8 years) (59.4 ± 6.5 pg/ml) or female belugas (54.1 ± 25.7 pg/ml). Among adult males, testosterone concentrations in blow demonstrated a seasonal pattern of secretion, with peak secretion occurring during the breeding season (February–April, 136.95 ± 33.8 pg/ml). Progesterone concentrations in blow varied by reproductive status; pregnant females (410.6 ± 87.8 pg/ml) and females in the luteal phase of the estrous cycle (339.5 ± 51.0 pg/ml) had higher (p < 0.0001) blow progesterone concentrations than non-pregnant females without a corpus luteum (242.5 ± 27.3 pg/ml). Results indicate that blow sample analysis can be used to detect variation in reproductive states associated with large differences in circulating testosterone or progesterone in belugas.

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General and Comparative Endocrinology