The elephant seal is the premier diver among seals and sea lions; it routinely holds its breath for 20 minutes as it dives to depths greater than 400 meters. This project investigates the physiology that allows this seal to make such remarkable dives. In particular, it is hypothesized that these seals can withstand extremely low levels of oxygen, and that this allows them to almost completely deplete their blood of oxygen during diving. Such extreme tolerance to low levels of oxygen is beyond that found in any mammal, and well below the oxygen levels found in humans attempting to climb Mt Everest without supplemental oxygen. In order to examine this hypothesis, seals will be equipped with backpack oxygen recorders which will provide a profile of the oxygen pressure in the blood as the seal dives. It is expected that the oxygen levels in the blood will be near zero by the end of the dive, and that it is this nearly complete utilization of the blood oxygen which allows elephant seals to dive as well as they do. This study will establish the physiological limits to which these seals push themselves. This is relevant to their ability to successfully find prey underwater and to their overall ecology in an environment that may be changing due to over fishing and global warming. In addition, the mechanisms which allow the seals to tolerate such low oxygen levels may be relevant to our understanding and treatment of various pathological states in humans in which tissues are exposed to inadequate oxygen or blood flow (hypoxemia or ischemia). Lastly, in addition to involving students directly in the research, this project will develop an educational website which will provide behavioral and physiological information on deep-diving whales, seals, penguins, and sea turtles.
