Summary
The diving behaviour of Adelie penguins Pygoscelis adeliae was studied with time-depth recorders at Dumont DUrville, 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 neretic 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 (22m/78s and 40m/102s with and without sea-ice, respectively). Comparisions 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.