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We used electronic time depth recorders to examine diving patterns of Adelie Penguins (Pygosce/is ade/iae) breeding near Palmer Station, Antarctica. Most hunting dives consisted of a rapid descent to depth, a period of bottom time at near-constant depth, and a rapid ascent to the surface. Most hunting activity occurred in bouts of consecutive dives to similar depths. Adelies foraged at depths between 3 and 98 m, with a mean of 26 m. ~escent and ascent rates averaged 1.2 and 1.1 m/s, respectively. Foraging was primarily diUrnal, but there was relatively little circadian change in foraging depth. The birds' overall hunting effort (cumulative bottom time) was concentrated between 0500 and 2100 at depths between 10 and 40 m. Bottom time decreased slightly with increasing depth but the correlation was weak. Dive duration was positively correlated with dive depth. Maximum dive duration was 160 s; most hunting dives lasted 60-90 s with a mean of73 s. Post-dive surface intervals averaged <=:::50% of dive duration. Time use efficiency during dive bouts (bottom time/[dive duration + surface interval]) decreased with increasing dive depth.Estimates of oxygen stores and diving metabolic rates indicate that the aerobic dive limit of Adelies is 46-68 s and that most hunting dives require some anaerobic metabolism. Use of anaerobiosis engenders an energy penalty and probably affects both the behavior and energetics of foraging.

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