The Antarctic fur seal is a large, hardy, charismatic animal, well adapted to the severe climate in the Southern Ocean area and its surrounding sub-Antarctic islands. In this species the male and female are, amongst all mammals, the most different from each other. Males are much longer and weigh about five times more than females. They also have a different fur color, adult males being dark brown and females and juveniles gray with lighter undersides. Pups are black when born and molt to silver-gray coloring when they are 2 to 3 months old. About one in a thousand has an unusual blonde-fur variant.
Antarctic fur seals have a wide distribution near the Antarctic Convergence in the Southern Ocean. Most of them breed on South Georgia but they also breed on other sub-Antarctic islands. When at sea they disperse widely. These seals spend much time in the ocean, where they hunt for food. Between breeding, females are able to travel long distances in open seas for a long time. On land, they prefer rocky habitats but are sometimes found on beaches and in areas of vegetation.
The Antarctic fur seal is a solitary animal, except when breeding and molting. Along with the Leopard seal, they are one of the most terrestrial seals. They are faster than humans when travelling across slippery rocks and amongst dense grasses. Once the breeding season is finished and the pups are weaned, the population moves to sea for the winter months of May to November. Where they go is not known or whether it is a dispersal or a directional migration, and some of the adult males and juveniles stay ashore for the whole year. When foraging, the seals usually dive to about 30 m for about two minutes. This species uses vocalizations to communicate. Males have two main calls, one a threatening roar directed at other males in response to a predator or other specific threat, the other a "huff-chuff" sound when moving around the breeding territories and interacting with females, being a sign of status. A female is able to roar and "huff-chuff" as well but she mainly communicates with her pups, using a high-pitched call as well as smell to establish the bond.
Antarctic fur seals are carnivores (piscivores), they mainly eat fish, krill, crustaceans, and cephalopods like squid and octopodes. In the South Georgia Islands, the mackerel icefish is the main prey. They may also prey on some smaller penguins.
Antarctic fur seals breed in colonies and are polygynous. Adult males arrive about one month before the breeding females, and establish territories. The breeding season lasts from mid-October through December. Each territorial male has an association with 1 to 27 females, the average being 15 females. Females bear pups conceived during the previous season and mate again about six to seven days after giving birth. A single pup is born after a gestation of 11-12 months, with implantation possibly being delayed. Births are from October to early November. While their mothers are away, the pups roam about and will interact with each other. Some pups enter the water by early January but until March they cannot swim well. A female will use vocalizations to seek her pup once back on land, confirming this by scent. Weaning takes place at around 117 days and the young become reproductively mature when they are three to four years old.
Antarctic fur seals nearly became extinct during the time of the 18th and 19th centuries, being hunted for their fur. Today the main threat to these seals is entanglement in debris created by humans, such as polypropylene straps, fishing nets and nylon string, which cause death by starvation or drowning.
Antarctic fur seals are the most abundant species of Fur seal. According to the Wikipedia resource, the total population size of the Antarctic fur seal is suggested to be 2 to 4 million individuals breeding at South Georgia, and 15,000 individuals at Heard Island. According to the IUCN Red List, the total Antarctic fur seal population is 700,000-1,million mature individuals. Overall, currently Antarctic fur seals are classified as Least Concern (LC) on the IUCN Red List, but their numbers today are decreasing.
Antarctic fur seals are key predators of krill and various species of fish and squid.