Abstract

As the impacts of human activities on marine ecosystems escalate, there is increasing interest in quantifying the sub-lethal physiological and pathological responses of wildlife.^1,2 Glucocorticoid hormones are commonly used to assess stress responses to anthropogenic factors. Although traditional methods to validate assays and measure circulating hormones are infeasible for free-swimming, large whales, immunoassays for fecal glucocorticoid metabolites (fGCs) have been successfully used in North Atlantic right whales (Eubalaena glacialis) to assess relative adrenal cortical activity.^3,4 Here, we compared baseline fGC levels in healthy right whales (n=113) to fGCs in whales that were live-stranded (n=1), chronically entangled in fishing gear leading to death (n=6), or quickly killed by vessels (n=5) to examine the relationship between fGCs and chronic vs. acute causes of injury and/or death. Paired serum and fecal samples were collected from a euthanized, live-stranded right whale (EG#3710), allowing comparison of glucocorticoid concentrations in two biological matrices. Both cortisol and corticosterone were present in serum (50.0, 29.0 ng/mL, respectively), and were highly elevated in this whale compared to values reported for other cetaceans. Fecal GCs were also extremely elevated (5740.7 ng/g), showing that this measure reflects adrenal cortical activation caused by extreme physiologic stress in a non-degraded sample. The duration of severe impacts experienced by right whales explained a significant amount of the variation in fGC concentration among whales (Linear Mixed Model: F_{3, 115.7} = 23.512; p<0.001). Thus, live-stranding (5740.7 ng/g) and chronic entanglement in fishing gear (mean±SE: 1856.4±1644.9 ng/g) resulted in significantly higher fGC concentrations compared to baseline levels in healthy right whales (mean: 51.7±8.7 ng/g; stranding: t_115.5=7.774, p<0.001; entanglement: t_115.3 = 3.191, p=0.002). By contrast, fGC concentrations in whales killed by vessel strike (mean: 46.2±19.2 ng/g) were similar to baseline levels in healthy whales (t_116.2=-0.061, p=0.951). Therefore, meaningful patterns in fGC levels related to the time course of injury or death persisted despite the potential for bacterial degradation of hormone metabolites in necropsy samples. Furthermore, extreme elevations of fGCs in live-stranded and chronically entangled right whales indicate massive activation of the hypothalamic-pituitary-adrenal axis secondary to severe chronic stress.⁵

Acknowledgements

The authors are grateful to the stranding networks, necropsy and disentanglement teams for their extraordinary efforts on behalf of North Atlantic right whales. We thank the members of the North Atlantic Right Whale Consortium for data sharing and embracing a collaborative approach that has greatly benefited right whale research and conservation. This work was supported by the NOAA/NMFS, Office of Naval Research, the Northeast Consortium, Island Foundation, Irving Oil, NEAq Internal Research Fund, Prescott Grant NA08NMF4390590, and NOAA CINAR Cooperative Agreement NA09OAR4320129. Fieldwork was conducted under NOAA Scientific Research Permits 1014, 655-1652, and 14233 issued to Scott D. Kraus, and Canadian Foreign Fishing/Research Licenses and Species at Risk permits from the Department of Fisheries and Oceans, issued to Scott D. Kraus and Moira W. Brown. All field research with right whales was approved by the New England Aquarium IACUC. Right whale necropsies were conducted under NOAA Permit #s 932-1905-MA-009526 and 932-1489-05 issued to Dr. Teresa Rowles, and disentanglement efforts were under Permit #932-1489 to the Center for Coastal Studies, and in Canada under permits issued by the Department of Fisheries and Oceans.

* Presenting author

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