Relationships Between Blubber and Respiratory Vapour Steroid Hormone Concentrations in Humpback Whales (Megaptera novaeangliae)

Respiratory vapour (blow) has been successfully used as a sample matrix for reproductive and adrenal endocrine assessments of some captive cetacean species. Given that the accuracy of blow hormone measurements can be affected by seawater contamination, variable sample volumes, and respiratory water dilution, it is a much more difficult technique to use for studies on wild cetaceans. Herein, we aimed to determine if blow sampling was a viable technique to measure reproductive and adrenal hormone concentrations in humpback whales (Megaptera novaeangliae). To achieve this, concentrations of progesterone, testosterone, oestradiol, and cortisol were measured in paired blow and blubber samples collected from free-swimming whales (n = 48). Hormone concentrations were compared between sample types and examined in relation to a whale's demographic class and the season when it was sampled. Testosterone concentrations were poorly correlated between sample types. In contrast, blubber concentration had a significant impact on the fit of the blow progesterone, oestradiol, and cortisol models (chi(2) = [11.52, 22.57, 6.121, p = [< 0.001, < 0.001, 0.013], respectively). There was little further evidence that blow hormone concentrations were driven by the physiological condition of a whale. Overall, the, strongest evidence came from one adult female who was presumed to be pregnant based on her blubber progesterone concentration (9.97 ng/g). This adult female displayed a blow progesterone concentration of 0.94 ng/mL, which was markedly higher than all other adult females and most other whales with the exception of two. Currently, however, blubber sampling is the preferred option for studying the endocrinology of humpback whales, primarily due to the ease of sample collection and robustness of hormone analyses. Further refinements and validation tests are required before blow hormone monitoring can he used as a non-invasive alternative.