Seasonal change in the foraging ecology of emperor penguins on the Mawson Coast, Antarctica

• Published in: Marine Ecology Progress Series
• Main Authors: Kirkwood, Roger, Robertson, Graham
• Format: Article in Journal/Newspaper
• Language: English
• Published: Inter Research 1997
• Subjects: Antarctic; Auster; Mawson Coast; Taylor Glacier; Antarc*; Antarctic Krill; Antarctica; antarcticus; Aptenodytes forsteri; Emperor penguins; Euphausia superba
• Online Access: https://oceanrep.geomar.de/id/eprint/51874/; https://oceanrep.geomar.de/id/eprint/51874/2/m156p205.pdf; https://doi.org/10.3354/meps156205

We investigated the foraging location, diving behaviour, dietary composition, feeding rates and foraging trip durations of emperor penguins Aptenodytes forsteri raising chicks at the Auster and Taylor Glacier colonies on the Mawson Coast of Antarctica in the winter, spring and early summer of 1993, to examine seasonal changes in the penguins' foraging ecology. As day-length increased after winter, the penguins' daily swimming time increased from 7.83 ± 1.50 h in August to 12.23 ± 1.25 h in September and 12.95 ± 1.24 h in October. Accordingly, the penguins' dive rate increased from 92.7 ± 28.5 to 149.4 ± 23.4 and 161.6 ± 19.3 dives d-1 in the respective months. The birds targeted prey in the vicinity of the continental slope mainly at depths <100 m, although some individuals frequently hunted at depths >200 m, and the maximum depth achieved was 438 m. Antarctic krill Euphausia superba were the most common prey taken overall, 41% of the diet by mass, and dominated the diets between August and October. The contribution of Antarctic krill to the diet reduced over time from 68% in August to 1% in early December. In November, the glacier squid Psychroteuthis glacialis dominated the diet (47 to 63%), and in early December the diet comprised various species of fish, Trematomus species (27%), Pagothenia borchgrevinki (24%), and Pleuragramma antarcticum (8%), and squid, P. glacialis (13%) and Alluroteuthis antarcticus (9%). The birds' prey consumption rates more than doubled between late winter and early summer, from 4.0 ± 1.0 to 8.7 ± 1.7 kg d-1 spent foraging; these values are equivalent to metabolisable energy intakes of 628 ± 134 and 1422 ± 308 kJ kg-1 d-1, respectively. During brooding (late winter to early spring), females spent less time at sea than males (8.7 ± 2.7 vs 17.7 ± 3.8 d); thereafter trip durations of both sexes were similar and declined from 15-19 d in spring to <10 d in early summer. Between hatching and about 1 wk prior to fledging each parent fed its chick 7 or 8 times. To raise a chick, ...