The diet of the Antarctic fur seal Arctocephalus gazella at Harmony Point, South Shetland Islands: evidence of opportunistic foraging on penguins?

The diet of non-breeding male Antarctic fur seals Arctocephalus gazella was investigated at Harmony Point, Nelson Island, South Shetland Islands, by the analysis of 523 scats collected from January to March 2001 and 2002. The composition of the diet was diverse and both, pelagic and benthic-demersal preys were represented in the samples. Overall, the Antarctic Krill Euphausia superba and fish were the most frequent and numerous preys, followed by penguins (presumably Pygoscelis antarctica), cephalopods (mainly squids) and gastropods. Among fish, Myctophids represented 86.5% and 65.8% of the fish mass in both seasons, with Gymnoscopelus nicholsi being the main prey. Interestingly, penguins were represented in the 39.0% and 31.9% of the samples in 2001 and 2002 and, as reflected by the reconstructed diet, was the main prey by mass (74.0% and 76.1%). The occurrence of penguins in the diet of A. gazella at Harmony Point is discussed and analysed in relation to the foraging strategy used by seals and to the temporal prey availability.