Speaker: Michelle Shero, Assistant Scientist II, Woods Hole Oceanographic Institution

Topic: The makings of marine mammal resilience: Capacity, tradeoffs, and new ways to measure them

 Understanding the mechanisms that underpin resilience, and when animals operate near their physiological limits, is integral to predicting how populations will respond to environmental change. Using approaches that range from molecular tracers to remote sensing technologies in pedigreed populations with long-term demographic records, I examine drivers of lifelong reproductive success and fitness. In Antarctic Weddell seals, females with the highest lifetime pupping success exhibit metabolic specialization linked in part to cortisol (‘stress hormone’) dynamics. In grey seals at Sable Island, reproductive energetics appear increasingly sensitive to environmental variability as the population nears carrying capacity. I demonstrate that selection for large oxygen stores has also led to substantial female-to-pup iron transfer during lactation, revealing previously unrecognized reproductive tradeoffs in marine mammals. Pinniped pups utilize this iron more efficiently than terrestrial mammals, and this transfer influences aerobic capacity in both adult females and offspring. In turn, variation in aerobic capacity interacts with environmental conditions to shape dive behavior from daily to seasonal timescales. By bridging traditional physiology with remote sensing, I draw on the extensive physiological datasets I have built across numerous field programs to guide best practices and interpretation as new technologies are adopted. My lab has also developed and applied non-invasive toolsets including drone-based 3D photogrammetry, biologgers, and thermal imaging-derived heart rate measurements to extend assessments of physiological tradeoffs across biological scales. Integrative and adaptive approaches provide new insight into the plasticity that shapes marine mammal resilience (and where constraints emerge), from individuals to populations.