Foraging habitats of southern elephant seals, Mirounga leonina, from the Northern Antarctic Península

MUELBERT M.; SANTINI M.F; WAINER I.E; SOUZA R.B; LEWIS, M; HINDELL M.

Hobart

Simposio; IV International Science Symposium on Biologging; 2011

CSIRO

Elephant Island (EI) is uniquely placed to provide southern elephant seals (SES) breeding there with potential access to foraging grounds in the Weddell Sea, the  frontal zones of the South Atlantic Ocean, the Patagonian shelf and the Western Antarctic Peninsula (WAP). Quantifying where seals from EI forage therefore provide insights into the types of important habitats available, and which are of particular importance   to elephant seals. Twenty nine SES (5 sub-adults males, SAM and 24 adults females, AF) where equipped with SMRU CTD-SLDRs during the post  breeding (PB 2008-2009) and post-moulting (PM 2007,2008, 2009, 2010) trips to sea. There were striking intra-annual and inter-sex differences in foraging areas emerged, with most of  the PB females remained within 150 km of EI, with one animal travelling down the WAP, while 16 out of the 20 PM females travelled down the WAP and foraged near the winter ice edge. Most PM males remained close to EI, in areas similar to those used by adults females several months earlier, although one male  spend the early part of the winter foraging on the Patagonian shelf. The waters of the Northern Antarctic Peninsula (NAP) contain abundant resources to support the  majority of the islands´ SES for the summer and the early winter, such that the animals  from this population have shorter migrations than those from most other populations. Sub-adults males are certainly taking advantage of these resources. However, females did not remain there over the winter months, instead they used the same waters at the ice-edge in the southern WAP that females from both King George Island  and South Georgia used. Female made more benthic dives than males again this contrasts with other sites where males do more benthic diving. Unlike most other populations studied to date, EI is a relatively southerly breeding colony located  on the Antarctic continental shelf. EI seals are using shelf habitats more than other SES populations but some individuals still employ open water foraging strategy. Sea- ice was also very influential for PB females SES with more foraging occurring in heavier pack ice where larger females used havier ice than smaller females. The study demonstrates the importance of shelf and slope habitat to elephant seals, but also highlighted the influence of sea-ice, fine scale bathymetry and local ocean  condition in determining foraging habitat.