This award will support a cooperative research project in biology between Professor Burney J. Le Boeuf, University of California at Santa Cruz, and Professor Yasuhiko Naito, National Institute of Polar Research, Tokyo, and colleagues from their respective institutions. The scientists will study diving behavior and foraging ecology of northern elephant seals, Mirounga angustirostris. Specifically they will study: 1) the development of diving in pups and juveniles, 2) measurement of swim velocity rates and feeding rates during diving, 3) location of foraging and routes taken at sea, 4) foraging energetics, and 5) the effect of weather variables on the free-ranging dive pattern. Diving performance will be studied by attaching diving instruments (time-depth recorders, swim velocity meters, radio transmitters) to seals at Ano Nuevo, California, before they go to sea. The U.S. and Japanese researchers bring complementary strengths to this project and Professor Naito's specifically-designed instruments will be critical to its success. The diving pattern of northern elephant seals--characterized by prolonged, continuous, and deep diving--is distinctive even among diving mammals. Recent findings are challenging long held interpretations of diving performance. These seals 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 3-8 months at sea. This collaborative study will clarify diving adaptations in pelagic seals. The findings will have important implications for how seals partition oxygen stores during foraging, manage anaerobic metabolites, and cope with compression effects. The results of the study will have practical applications to fisheries biology and marine mammal management, and will have broad implications for foraging ecology, understanding the diving adaptations of aquatic vertebrates, and studying diving behavior and physiology.
