Diving behaviour of Adélie penguins (Pygoscelis adeliae) at Dumont D'Urville, Antarctica: nocturnal patterns of diving and rapid adaptations to changes in sea-ice condition

The diving behaviour of Adélie penguins (Pygoscelis adeliae) was studied with time-depth recorders at Dumont D'Urville, Antarctica, during the breeding seasons in 1995/1996 and 1996/1997. We studied penguins foraging at all breeding stages, in various sea-ice conditions. For the first time in this species we observed nocturnal patterns of diving as the penguins dived more frequently and spent more time underwater around midnight than around noon. This behaviour may be related to the abundance of neritic krill, Euphausia crystallorophias, in the diet. Dive depth and duration varied extensively over the cycle, and appeared related to sea ice conditions rather than representative of the locality (22 m/78 s and 40 m/102 s with and without sea-ice, respectively). Comparisons with other studies showed that different diving behaviour previously observed in different localities can also occur at the same locality, and in some cases over a single foraging trip of a single penguin when short-term variation of external conditions occurred.