Interaction between stress physiology, pollutants, foraging success, and reproduction in elephant seals

By experimental manipulation, we examined the effects of pollutants (Mercury) acoustic disturbance and reproductive outcomes in northern elephant seals where individuals were exposed to acoustic disturbance and/or increased cortisol (stress hormone). We measured health metrics (e.g., energy stores, allostatic load, stress hormones, immune status, contaminant burden) and vital rates (survival and reproductive output) before and after the post-breeding foraging trip. We compared those metrics to at-sea foraging behavior (dive duration, depth, trip duration, etc.). Across these experimental groups, a natural variation in mercury burden is associated with the foraging strategy. We found that mercury burden has additive and synergistic effects with cortisol on the endocrine (T3, T4, and rT4) and immune (IgG) systems. We also found a significant relationship between energy gain over a foraging trip (foraging success) and circulating blood cortisol level (GLMM p < 0.001). Females with very poor energy gain had cortisol levels as high as 20 ug dl-1, a value 20 times normal levels. These females had a lower probability of pupping the following season. We found no differences in spatial distribution or diving depth associated with lower rates of energy gain in either our experimental post-breeding data set (n=63) or our long-term data set across post-breeding and post-molting trips (n = 463). Elephant seals provide an excellent model for studying the interaction of multiple stressors on vital rates that can be applied to more difficult-to-study species. Office of Naval Research (ONR) and RC20-C2-1284 from the Strategic Environmental Researchand Development Program (SERDP) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.