Population status of southern elephant seals (Mirounga leonina) at Peninsula Potter breeding colony, Antarctica

Abstract

Southern elephant seals (Mirounga leonina) are apex predators that spend several months at sea feeding over vast areas. Their population trends are related to food availability during winter, which in turn is influenced by environmental conditions; thus, fluctuations in their populations reflect changes in the ecosystems. Although population trends for this species are available for large populations, there are still small colonies for which information is scarce, as is the case for the colony located at Peninsula Potter, South Shetland Islands. At this colony, field censuses of the number of breeding females conducted from 1995 to 2018 revealed an overall decline of 11.9% at an annual rate of 0.6%. However, contrasting trends before and after 2008 were observed. A decrease of 46.5% at an annual rate of 4.6% was registered before 2008, while for the subsequent period (2008–2018) the number of females increased by 64.5% at an annual rate of 5%. A positive association was observed between the extent of sea ice in winter foraging areas and population numbers between 1995 and 2008. The females of this colony feed on the edge of the sea ice, so in years of low sea ice extension the effort required to reach these areas is greater. This could lead individuals to choose to breed in areas closer to their feeding grounds in order to avoid the energetic expenditure of body reserves acquired during winter that would sustain the return trip to their natal colony.