Exploration of Fecal Glucocorticoid Metabolites in the Bottlenose Dolphin (Tursiops truncatus) Under Human Care by Enzyme Immunoassay

While the bottlenose dolphin (Tursiops truncatus) is the most studied and widespread cetacean in captivity, studies assessing its welfare have been studies assessing its welfare have been developed only recently. Several studies focus on a potential indicator of stress: fecal glucocorti coid metabolites (FGM) concentration, which is expected to increase when the hypothalamic-pituitary-adrenal (HPA) axis is activated. However, a lack of studies that consider the biological variation of FGM concentrations related to sex and seasons, and the link to dolphins' reproductive status still impairs our ability to use it for monitoring purposes in the context of welfare assessment. Therefore, it is essential to explore and assess the potential influence of these factors on the variation of FGM concentrations in dolphins. In parallel, non-invasive sampling and methods of measurement should be developed. Thus, the authors performed a methodological validation of enzyme immunoassay (EIA) for FGM in bottlenose dolphins and studied the influence of reproductive status, sex, and seasons on FGM concentrations. The findings showed significantly higher FGM dolphins, and significantly higher FGM concentrations in pregnant females than in other dolphins, and significantly higher FGM concentrations in males than in nonpregnant females. Moreover, only males showed higher concentrations during spring than during autumn and winter. In parallel, megestrol acetate used for male contraception and pregnancy in females appeared to inhibit and stimulate the HPA axis, respectively. This study creates new opportunities to use EIA as a tool for monitoring FGM concentrations in dolphins and provides new data on its biological variations.

Automated summary

This study explored the biological variations in FGM concentrations in bottlenose dolphins, finding significantly higher FGM concentrations in pregnant females and males compared to other dolphins, with males showing higher concentrations during spring. Additionally, megestrol acetate appeared to have different effects on the HPA axis based on sex and reproductive status in dolphins.