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UBC Theses and Dissertations

Fecal hormone metabolites as indicators of stress in the southern and northern resident killer whale (Orcinus orca) populations in coastal waters of British Columbia, Canada Yehle, Kaitlin Elizabeth


Fecal hormone metabolite analysis is increasingly used as a non-invasive method to evaluate physiological stress in free-ranging animals, especially those of conservation concern. In this study, it is applied to investigate stress in the Northeast Pacific southern and northern resident killer whale (Orcinus orca) populations. The southern resident killer whale population is listed as endangered, as the population is small and declining. Despite sharing a similar diet and environment, the northern resident population shows greater reproductive success and has increased in recent years. It has been hypothesized that the southern residents are more physiologically and nutritionally stressed than the northern residents, due to anthropogenic threats of reduced prey availability, acoustic and physical disturbance, and environmental contaminants. Fecal samples were collected from both populations along the coast of British Columbia, Canada, in July and August of 2018-2019. I first validated four commercially available enzyme-linked immunosorbent assays for quantifying steroid (progestogens, androgens, and glucocorticoid) and thyroid hormone metabolites in killer whale feces, then compared concentrations of fecal glucocorticoid and thyroid metabolites between the southern and northern resident populations as indicators of stress. Mean fecal progestogen metabolites (fPM) were highest in pregnant females, higher in females (non-pregnant) than males, and were successfully used to determine pregnancies. Mean fecal androgen metabolites (fAM) were highest in pregnant females and sprouter (adolescent) males, and were greater in males relative to non-pregnant females. Mean fecal glucocorticoid metabolites (fGCM) were higher in pregnant females than non-pregnant females and males, but were not significantly different between the southern and northern resident populations. There were no significant differences in mean fecal thyroid metabolites (fTHM) among any demographics, but mean fTHM was significantly lower in the southern resident population than the northern resident population (P < 0.05), suggestive of heightened chronic nutritional stress. Though sample sizes were small, these findings advance our knowledge of marine mammal physiology and assist with understanding stress and the threats affecting the health and status of the endangered southern resident killer whale population.

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