title: Bottom-up regulation of a pole-ward migratory predator population.
abstract: As the effects of regional climate change are most pronounced at polar latitudes, we might expect polar-ward migratory populations to respond as habitat suitability changes. The southern elephant seal (Mirounga leonina L.) is a pole-ward migratory species whose populations have mostly stabilized or increased in the past decade, the one exception being the Macquarie Island population which has decreased continuously over the past 50 years. To explore probable causes of this anomalous trend, we counted breeding female seals annually between 1988 and 2011 in order to relate annual rates of population change (r) to foraging habitat changes that have known connections with atmospheric variability. We found r (i) varied annually from -0.016 to 0.021 over the study period, (ii) was most effected by anomalous atmospheric variability after a 3 year time lag was introduced (R = 0.51) and (iii) was associated with sea-ice duration (SID) within the seals' foraging range at the same temporal lag. Negative r years may be extrapolated to explain, at least partially, the overall trend in seal abundance at Macquarie Island; specifically, increasing SID within the seals foraging range has a negative influence on their abundance at the island. Evidence is accruing that suggests southern elephant seal populations may respond positively to a reduced sea-ice field.
authors.affiliation: Australian Antarctic Division, , 203 Channel Highway, Kingston, Tasmania 7050, Australia, Institute for Marine and Antarctic Studies, University of Tasmania, , Hobart, Tasmania 7001, Australia, Climate Change Research Centre, University of New South Wales, , Sydney, New South Wales 2052, Australia, Department of Primary Industries, Parks, Water and Environment, , 134 Macquarie Street, Hobart, Tasmania 7000, Australia.
authors.forename: John
authors.initials: J
authors.lastname: van den Hoff
authors.forename: Clive R
authors.initials: CR
authors.lastname: McMahon
authors.forename: Graham R
authors.initials: GR
authors.lastname: Simpkins
authors.forename: Mark A
authors.initials: MA
authors.lastname: Hindell
authors.forename: Rachael
authors.initials: R
authors.lastname: Alderman
authors.forename: Harry R
authors.initials: HR
authors.lastname: Burton
mesh_terms: D000818:Animals; D000864:Antarctic Regions; D057231:Climate Change; D017753:Ecosystem; D005260:Female; D046448:Ice Cover; D011157:Population Dynamics; D012098:Reproduction; D046048:Seals, Earless / Q000502:physiology*; D013648:Tasmania
keywords: Mirounga leonina; climate change; rate of population change; sea-ice duration; southern annular mode; winners and losers