Abstract:
Marine top-predators show fidelity to foraging areas with predictable high-quality food patches.
Areas of predictable prey yield are of conservation importance and telemetry data aid in
identifying such areas. This study examined colony specific and intra-individual foraging site
fidelity of lactating Subantarctic fur seals (Arctocephalus tropicalis) from Marion Island
(46°54‟S, 37°45‟E) during summer and winter, comparing commitment to foraging areas across
seasons. Thirty-one females were tracked in 2009-2013 resulting in 111 foraging trips for
analyses. Inter-annually, preferred foraging areas in summer were consistently ≈200 km due east
of Marion Island towards the Gallieni Rise. Summer individuals' core utilization areas
overlapped by an estimated 32.84% (CI: 24.53% - 41.94%). Seals responded to a decrease in
regional productivity in winter by foraging in more distant alternative areas. In winter,
individuals changed their travelling direction to north-east of Marion Island and foraged further
afield, around the Del Caño Rise and along the South-west Indian Ridge. Despite preferring
some foraging areas in winter, there was a low amount of overlap 6.03% (CI 4.02% - 9.16%) of
individual core utilization areas. The foraging grounds identified in this study have not been
included in prior conservation assessments and are important in conserving for this globally significant, and currently declining, population of Subantarctic fur seals and perhaps other toppredators
breeding at Marion Island as well. Differences between winter and summer preferred
foraging areas highlight the importance of sampling during different seasons when using
telemetry data for the identification of potential pelagic conservation areas.
