Leopard Seals, Hyrurga leptonyx (Pinnipedia), at Macquarie Island from 1949 to 1979

Abstract

The annual abundance of leopard seals recorded at Macquarie I. since 1949 has regularly oscillated between a few and 100-200 individuals every 4 or 5 years. Only non-breeding individuals occur, mainly 1-, 2- and 3-year-old seals that are sexually immature, with both sexes in approximately equal numbers. The seals are present between late June and early December with greatest numbers in early August. The results of the tagging of 278 leopard seals in 1976-78 show that most of the seals are highly mobile and leave the island 1 or 2 days after they first arrive, but some may remain for up to 104 days. Each year a few of the seals tagged in the preceding year have returned to the island. In 1977 tagged seals were resighted at Campbell I. and Bicheno, Tas., providing the first detailed information on the movements of individuals leopard seals over long distances. Periodic dispersal of large numbers of non-breeding leopard seals into subantarctic and temperate seas has produced the observed regular peaks in relative abundance. Possible causes of this dispersal are discussed.