January 8, 2001 Publications Daniel Costa An article on New Zealand sea lions by professor of ecology and evolutionary biology Daniel Costa was featured on the cover of the December issue of the Journal of Experimental Biology. The New Zealand sea lion dives deeper and longer than any of the other eared seals (which include sea lions and fur seals). Costa and his coauthor, Nicholas Gales of the New Zealand Department of Conservation, investigated the New Zealand sea lion's diving behavior and foraging energetics. The researchers recorded dives as deep as 550 meters (1,800 feet) and as long as 11.5 minutes. Typical dives were around 4 minutes long and 123 meters (400 feet) deep. Costa was interested whether the New Zealand sea lion is physiologically adapted for prolonged diving, perhaps by lowering its metabolic rate during dives. The study, however, showed that its diving ability is not explained by a reduced metabolic rate. New Zealand sea lions use a "burst and glide" strategy to conserve energy during dives. They also have a large blood volume compared to related species, giving them increased oxygen-storage capacity, but Costa said the animals appear to be operating near their physiological limits during dives. In comparing New Zealand sea lions with Antarctic fur seals, which make shallow short dives, the researchers found that the two species had surprisingly similar rates of energy expenditure while at sea. How they budgeted their energy expenditures differed, however, reflecting differences in the distribution of their prey.