Emperor penguins (Aptenodytes forsteri) and leopard seals (Hydrurga leptonyx) are iconic, top predators in Antarctica. Understanding their physiological ecology is essential to the assessment of their adaptability to the threats of climate change, pollution, and overfishing. The proposed research has multipronged objectives. Prior results suggest that Emperor penguins have flexible (vs. static) aerobic dive limits (ADL) that vary with the type of dive, and that the role of heart rate in utilization of oxygen stores also varies with dive type. A series of physiological measurements are proposed with backpack electrocardiogram recorders, that will allow further delineation of patterns and interrelationships among heart rate, dive behavior, and oxygen stores. Importantly, the research will be done on free diving emperors, and not individuals confined to a dive hole, thereby providing a more genuine measure of diving physiology and behavior. A separate objective is to examine foraging behavior of leopard seals, using a backpack digital camera and time depth recorder. Leopard seal behavior and prey intake is poorly quantified, but known to be significant. Accordingly the research is somewhat exploratory but will provide important baseline data. Finally, the P.I. proposes to continue long term overflight censuses of Emperor penguin colonies in the Ross Sea. Broader impacts include collaboration with National Geographic television, graduate student training, and development of sedation techniques for leopard seals.
This project investigated heart rate regulation in dives of emperor penguins at sea in order to understand how emperor penguins can dive as deep as 500 meters and as long as 10-15 minutes on a single breath of air. It was found that heart rate became ever slower as the penguins dove deeper and longer. During the bottom segments of 500-meter deep dives, heart rate was routinely near 10 beats per minute (in comparison to pre-dive rates of 220 beats per minute and resting heart rates near 50 beats per minute). Such low heart rates decrease peripheral blood flow and tissue oxygen consumption as well as blood uptake of oxygen and nitrogen from the lungs at depth. This heart rate response not only conserves oxygen but also limits nitrogen absorption and the risk of decompression sickness. The similarity of the deep-dive heart rate response of emperor penguins to that of deep-diving sea lions suggests that this cardiovascular response to deep dives is characteristic of all higher vertebrates that dive deep on inspiration. This project also conducted censuses at all the emperor penguins colonies of the Ross Seal. Oversall, through 2012, the general population appeared stable. However, marked annual fluctuations occurred. From 2008 to 2010, the count at the Coulman Island colony (the largest in the world) decreased by 50%. Although it has gradually recovered, the causes of the declines and shifts in colony sizes are unclear. The planned investigation of leopard seal foraging behavior and its impact on the penguin colony was prevented by sea-ice conditions and lack of access to the animals. Broader impacts included creation of a National Geographic educational website and television documentary. The project supported nine publications in scientific journals, two book chapters, and an educational television documentary in collaboration with National Geographic Television. Three graduate students and two post-doctoral fellows received training.
