Bottom-up regulation of a pole-ward migratory predator population

• Published in: Proceedings of the Royal Society B: Biological Sciences
• Main Authors: van den Hoff, J, McMahon, CR, Simpkins, GR, Hindell, MA, Alderman, R, Burton, HA
• Format: Article in Journal/Newspaper
• Language: English
• Published: Royal Soc London 2014
• Subjects: Biological Sciences; Ecology; Marine and Estuarine Ecology (incl. Marine Ichthyology); Elephant Seal; Macquarie Island; Mirounga leonina; Sea ice; Southern Elephant Seal
• Online Access: https://doi.org/10.1098/rspb.2013.2842; http://www.ncbi.nlm.nih.gov/pubmed/24619437; http://ecite.utas.edu.au/92725

As the effects of regional climate change aremost pronounced at polar latitudes,we might expect polar-ward migratory populations to respond as habitat suitabilitychanges. The southern elephant seal ( Mirounga leonina L.) is a pole-wardmigratory species whose populations have mostly stabilized or increased inthe past decade, the one exception being the Macquarie Island populationwhich has decreased continuously over the past 50 years. To explore probablecauses of this anomalous trend, we counted breeding female seals annuallybetween 1988 and 2011 in order to relate annual rates of population change( r ) to foraging habitat changes that have known connections with atmosphericvariability.We found r (i) varied annually from 20.016 to 0.021 over the studyperiod, (ii) was most effected by anomalous atmospheric variability after a3 year time lag was introduced ( R = 0.51) and (iii) was associated withsea-ice duration (SID) within the seals foraging range at the same temporallag. Negative r years may be extrapolated to explain, at least partially, theoverall trend in seal abundance at Macquarie Island; specifically, increasingSID within the seals foraging range has a negative influence on their abundanceat the island. Evidence is accruing that suggests southern elephant sealpopulations may respond positively to a reduced sea-ice field.