The Antarctic fur seal, Arctocephalus gazella, is a species of eared seal inhabiting the cold waters of the Southern Ocean. Like all fur seals, they are characterized by their dense fur, which historically made them a target for commercial sealing. This exploitation in the 18th and 19th centuries drove the species to the brink of extinction. However, with the cessation of widespread hunting and the implementation of protective measures, their populations have made a significant comeback.
Geographic Distribution
Antarctic fur seals have a circumpolar distribution in the subantarctic and Antarctic marine environments. Their habitat is largely defined by the Antarctic Convergence, a distinct oceanographic boundary where cold Antarctic waters meet warmer subantarctic waters. This zone is characterized by high marine productivity, which supports the seals’ dietary needs. While they are found on numerous islands, their population is overwhelmingly concentrated in one key area.
The island of South Georgia is the primary habitat for this species, hosting over 95% of the global population. This makes it the densest marine animal aggregation on the planet during the breeding season. Other smaller, but still notable, breeding colonies are established on islands such as the South Shetland, South Orkney, and South Sandwich Islands. Seals from the large South Georgia population have also been observed migrating to establish new colonies on other subantarctic islands.
Breeding and Rearing Grounds
For breeding and raising their young, Antarctic fur seals require specific terrestrial habitats known as rookeries. They select rocky or pebble-strewn beaches for these colonies, which can sometimes extend from the shoreline into adjacent areas of tussock grass. These locations provide the necessary space and terrain for the dense congregations that characterize their breeding season.
Beginning in mid-October, adult males arrive ashore to establish and fiercely defend territories before the females arrive. Successful males form harems, which can include up to 20 females, and they will remain on land without feeding for about a month to protect their group. Females arrive already pregnant from the previous season and give birth to a single pup shortly after coming ashore.
Pups are born with a black coat and are nursed by their mothers for approximately four months. During this period, the female alternates between nursing her pup for one to two days on land and undertaking foraging trips at sea to find food. This cycle of feeding and nursing continues until the pup is weaned.
Foraging Areas and Diet
The marine environment is where Antarctic fur seals spend much of their lives, hunting for sustenance. Their primary foraging grounds are the cold, nutrient-rich waters of the Southern Ocean, with the Scotia Sea being a particularly important area. These foraging trips can span considerable distances into the open ocean, as seals search for dense patches of their preferred prey.
Antarctic krill constitutes the vast majority of their food, making up about 95% of their diet in areas like South Georgia. A single seal can consume about a ton of krill annually. They supplement this with various species of fish and squid. Foraging patterns differ based on breeding status; nursing mothers tend to make shorter, more frequent trips to stay close to their pups, while males and non-breeding females may travel farther afield.
Threats to Their Environment
The habitat of the Antarctic fur seal faces significant environmental challenges, with climate change posing a substantial threat. The warming of the Southern Ocean directly impacts the availability of their primary food source, Antarctic krill. Krill populations are dependent on sea ice for part of their life cycle, and diminishing ice cover can lead to a reduction in their numbers. In years when krill are scarce, the effects are felt immediately within the seal colonies.
Another environmental pressure comes from marine debris. Entanglement in discarded fishing nets, plastic strapping, and other synthetic materials can cause injury and death to individual seals. Furthermore, the potential for increased human activity, including shipping and tourism in the Antarctic, raises concerns about disturbance to their breeding and hauling-out sites.