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This research examines the foraging energetics and diving behavior of the Australian sea lion, Neophoca cinerea. We examine whether the foraging ecology of the Australian sea lion is typical for an animal that has evolved to exploit benthic habitats. Such a strategy is in marked contrast to those utilized by some seabirds and other pinnipeds that feed in the midwater, where travel and search components of the time at sea become more important. Onshore and at-sea field metabolic rates (FMR) were measured using doubly labeled water in lactating sea lions at Kangaroo Island, South Australia, during the winter of 1988 (early lactation, breeding season 1) and the summer of 1990 (early lactation, breeding season 2). Dive behavior was also measured with dataloggers during these seasons, as well as in the summer of 1991 (late lactation, breeding season 2). The foraging behavior of Neophoca cinerea indicated that it works hard to exploit benthic habitats in the waters around its breeding site. Sea lions maximized time spent at or near the benthos, with 61% of each dive and 35% of their time at sea being spent at the deepest 20% of the dives. The dive pattern was characterized by almost continuous diving when at sea, with 57.9% of their time at sea spent at depths [greater than or equal to] 6 m, and dive rates of 10.7 dives/h. Mean surface intervals (1.0-1.9 min) accounted for only 42% of mean dive durations (2.2-4.1 min). Mean dive depths ranged from 41.5 m to 83.1 m, with maximum dives ranging from 60 m to 105 m. The energetic costs of this strategy are high when compared with those of other otariids: the mean at-sea FMR was 7.05 [+ or -] 0.99 W/kg. We report seasonal variability in foraging energetics and dive behavior that is likely to be sensitive to regional oceanography, the maintenance costs of female sea lions and their offspring, and the distribution and behavior of their prey. Further, we note that Australian sea lions are functionally adapted to benefit from benthic foraging strategies because their larger size and insulating blubber convey an advantage over the generally smaller sympatric fur seals that would have a decrease in air/ fur insulation with compression at deeper depths and would experience greater water infiltration of the fur with longer dives. Key words: aerobic dive limit; Australian sea lion; benthic foraging; diving behavior; doubly labeled water; foraging ecology; foraging energetics; fur seals; interannual variability; Neophoca cinerea; sea lions; seasonality.

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1523-1739.2006.00472.x Byline: RANDALL R. REEVES (*), NICHOLAS J. GALES ([dagger]) Author Affiliation: (*)Okapi Wildlife Associates, Hudson QC J0P 1H0, Canada, emailrrreeves@total.net ([dagger])Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia Article History: Paper submitted August 29, 2005; revised manuscript accepted February 16, 2006.

Author(s): Nicholas J. Gales [1]; Toshio Kasuya [2]; Phillip J. Clapham [3]; Robert L. Brownell, Jr [4] Eighteen years after initiating scientific whaling in Antarctic waters, Japan presented a new [...]