Fur seals on Macquarie Island

Antarctic fur seal sleeping. AAD photo

Macquarie Island was discovered by sealers in July 1810. Harvesting commenced immediately and by about 1820, the sealer's had taken almost 200,000 skins and in the process had eliminated the entire population. The identity of the original species is unknown.

Fur seal were present in small numbers when the ANARE base on Macquarie Island was established in 1948, although none were breeding at that time. In 1954, 130 years after the cessation of sealing, the first fur seal pup was born. Annual pup production increased slowly up until the 1980s when the population began to increase exponentially.

Juvenile subantarctic fur seal. AAD photo

Macquarie Island is unique among fur seal populations in that it contains three species, Antarctic (Arctocephalus gazella), subantarctic (A. tropicalis) and New Zealand fur seals (A. forsteri). The breeding population consists mainly of Antarctic and subantarctic fur seals, although New Zealand fur seal males hold breeding territories and occasionally females breed also.

Male Antarctic fur seal. AAD photo

The recent rapid increase in pup production at Macquarie Island is driven primarily by the expanding Antarctic fur seal population (about 13% per year), which accounts for about 65% of the entire population. In recent seasons the subantarctic fur seal population has begun to show a significant annual increase also (9% per year) and accounts for about 20% of the entire fur seal population. Antarctic, subantarctic and New Zealand fur seals hybridise at Macquarie Island, with hybrids accounting for about 15% of the population.

Adult subantarctic fur seal. AAD photo

A long-term research program, based at the Sea Mammal Ecology Group, La Trobe University, has been established to monitor the recovery and biology of the fur seal population. The study commenced in 1986. Each summer, 2-3 researchers spend around five months on the island, assessing annual changes in pup production of each species, and the extent and trends in hybridization.

They also investigate changes in population demography (survival, recruitment and female reproductive success), and how changes in local oceanographic conditions (as determined from satellite derived data on sea surface temperature and primary production) affect the demographic performance of fur seals, both at annual and lifetime scales. This includes an assessment of how readily seals are able to find food resources around the island by collecting data on the provisioning rates of lactating females, and the growth rates of their pups. The research has an applied management and conservation focus, and is undertaken with a strong animal welfare and minimal impact ethic.

For further information, visit the Ecology Group's website at La Trobe university.