Abstract
Southern elephant seals Mirounga leonina breed and moult on many subantarctic islands during the austral spring and summer. In the Kerguelen Province the subpopulations of M. leonina at Kerguelen (49°21′S, 70°12′E), Marion (46°54′S, 37°45′E) and Possession (46°25′S, 51°45′E) Islands have declined since 1970 and their present status at Heard Island (53°05′S, 73°30′E) is unknown. Population studies during their terrestrial phase have failed to explain the declines. Long distance movements of individuals between the subpopulations in question and also the Vestfold Hills, Antarctica (68°35′S, 77°58′E) have been recorded. The availability of food resources, competition with rapidly increasing fur seal populations and competition with fishing fleets have all been implicated in their decline. These explanations assume that communal feeding grounds are utilized. As they are predators entirely dependent on marine feeding, a study of their spatial and temporal distribution during their pelagic existence is of the utmost importance. Parameters describing growth, reproduction rates, population dynamics, and feeding ecology of the subpopulations in the Kerguelen Province may furthermore serve as indices of change within the marine ecosystem. The presence of a relatively large and predominantly male nonbreeding population of M. leonina at the Vestfold Hills in Antarctica which originates from the Kerguelen/Heard Island group, and which shows annual return, should be included in the marking and monitoring studies of the Kerguelen stock of southern elephant seals. Studies here, including an update of the size and social structure of the Heard island subpopulation, may elucidate the observed decline of, in particular, the adult bull component of the breeding stock.
Published Version
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