Population changes, movements of southern elephant seals on Crozet and Kerguelen Archipelagos in the last decades

Abstract

The elephant seal populations breeding on the Crozet and Kerguelen Archipelago were surveyed during the eighties. Elephant seals were observed moving between Kerguelen, Amsterdam, Heard Islands and Vestfold Hills and between Crozet and Prince-Edward Archipelagos. No exchanges were observed between Crozet and Kerguelen Archipelagos suggesting that the two populations are more isolated than previously stated. On the Crozet Archipelago, since 1966, the Possession Island population showed at 70% reduction in numbers of cows ashore and the population is still decreasing. On Kerguelen Island there has been a decline of 44% from 1956 to 1989 but the population appears to have stabilized since 1984. It is suggested that elephant seal populations in the Southern Indian Ocean may have been affected by a change at the trophic level over the last four decades. But the highest rate of decrease observed on the Crozet Archipelago and the fact that the population is still decreasing may be explained by additional factors, in particular by killer whale predation.