Foraging habitat and food intake of satellite-tracked king penguins during the austral summer at Crozet Archipelago

The relationships between the foraging strategy of seabirds, hydrographic features and food availability are poorly understood. We investigated the movements at sea, time spent per oceanic sector, food intake, and diet of king penguins Aptenodytes patagonicus in the Crozet Islands (Southern Indian Ocean) during summer, as a function of the position of major frontal zones. Fifteen trips at sea were monitored using satellite transmitters over 3 austral summers (1992 to 1994). During each season, satellite transmitters were used in conjunction with stomach temperature recorders in order to investigate feeding activity. The at-sea distribution of king penguins was closely related to the localisation of major hydrographic frontal systems. Intense prospecting areas were observed mainly in zones corresponding to the northern Limit of the Polar Front (500 to 51 degrees S), southern limit of the Sub-Antarctic Front (44.50 degrees to 45 degrees S), and a zone between 47 degrees and 48 degrees S. During trips directed south, 2 distinct phases based on travelling speed were detected. The myctophids Electrona carlsbergi, Krefftichtys anderssoni and Protomyctophum tenisoni dominated the diet. The estimated average amount of food ingested per day at sea was 2.4 kg. Between 17 and 64 kg of food was captured during 7 to 25 d at sea. Approximately 80% of the food intake occurred during the first phase of the trip. Food intake was related to trip duration and relative amount of time spent in particular oceanic sectors. The sections 47 degrees to 48 degrees S and 48.5 degrees to 50.50 degrees S appeared particularly favorable for food intake, the latter coinciding with the northern Limit of the Polar Front, King penguins fed intensively on several distinct patches when traveling towards the Polar Front, The foraging range seems to be related to the foraging success during the first phase of the trip. The foraging strategy of king penguins during the summer favors displacements toward frontal zones where food availability is optimal.