Female northern elephant seals have a distinctive diving pattern. They dive deeper than other marine mammals (maximum depth of 1250 m), spend brief periods on the surface between dives (less than 3 minutes), and dive continuously for three months at sea. The present studies will determine whether a cross section of adults, juveniles and pups exhibit the same pattern, test for the effects of pregnancy on diving performance, delineate the bioenergetic consequences of extreme sexual dimorphism on foraging, and provide vital information on the development of diving. Hypotheses concerning metabolism, energy expenditure, and foraging strategies will be tested by measuring swim velocities, matching these to other dive characteristics, and relating surface interval duration to diving effort. Six different diving instruments will be used to record dive depth, dive duration, surface interval duration and swim speed. Changes in physiological variables associated with the development of diving performance (e.g., blood volume, myoglobin concentration, hematocrit and oxygen utilization) will be monitored in pups and yearlings in the field and in diving tanks in the laboratory. Prolonged, continuous deep diving is unusual and challenges several long held interpretations of diving performance. The present studies will clarify diving adaptations in pelagic seals. These studies have important implications for how seals partition oxygen stores during foraging, manage anaerobic metabolites, and cope with compression effects.
