South American fur seals are members of the family that sea lions belong to (Otariidae, meaning eared seals). On land they are more agile than the 'earless' seals, due to being able to move their back limbs forward under, their body raising it as they move. Males and females differ in appearance, as the male is much larger and heavier, having a mane of long hair over its thick neck and shoulders. Adults are blackish-gray, and sometimes have a slightly grizzled appearance. Females and sub-adult males are dark brown to grayish-black, and have paler underparts.
The South American fur seal, as its common name suggests, occurs along both the Pacific and Atlantic coasts of South America, and has a discontinuous distribution that runs from Peru to Chile, as well as from southern Brazil to Tierra del Fuego, and then around the Falkland Islands. Most of the seals are concentrated on Uruguay’s coast, and they are also sometimes reported outside of their normal range, off the coast of Chile in the Juan Fernández Islands, and in Colombia. These animals breed on land, and colonies are generally found in caves, on rocky coasts, on ledges above the shorelines, or in areas that are strewn with boulders. This species’ distribution at sea is little known, but they are thought to primarily occur in seas around the coast and above the continental shelf and slope, though they sometimes travel to over 600 km offshore.
South American fur seals are social animals and live alongside each other in rookeries that are along the shore. These seals often fish during the night in groups. Most of the time they spend in the water swimming, however, they live on land during the breeding season. Although seasonal movements of males and juvenile seals are not well understood, most females stay near the breeding grounds during the year. At sea, this species is often seen resting or travelling in groups, spending a lot of time grooming when at rest at the surface. These seals communicate vocally and through touch. When they communicate with each other over long distances they use vocalizations.
South American fur seals are carnivores (piscivores and molluscivores), they eat anchovies, shrimp, lobster, krill and squid, location having a role in the main dietary content. In Peru and Uruguay they eat anchovies. The ones closer to Brazil eat shrimp. In Chile they tend to eat krill, specifically lobster krill.
This species is polygynous, males mating during each breeding period with more than one female. Males compete for particular areas along the shoreline between October and December for the purpose of establishing a territory for them and the females they are mating with. The dominant males gain the largest territory and the most females. One pup is born per breeding season after a gestation of 8 to 12 months. Mothers usually wean their pups after 6 to 12 months, but sometimes not until 3 years, when the mother may be nursing two pups. The female mates with a male again within 7 to 10 days after the birth. Males reach maturity at about age of 7, but many do not mate until 8 years old. Females reach maturity at about the age of 3.
South American fur seals have for a long time been hunted for their fur, skin and oil. 1515 was when commercial hunting first began and it has continued in Uruguay until very recently. Some illegal poaching continues, particularly in Peru. Others threats include pollution, oil spills, entanglement accidentally in fishing gear, illegal hunting as bait for king crab fishing, and reduction in prey due to intensive commercial fishing. This species can also be heavily impacted by El Niño events, which affect ocean currents, decreasing the supply of food and causing many deaths of seals of all ages. This natural phenomenon, which causes the ocean surface water to heat up and lasts for a number of months, has the most serious impact on the seal populations in Peru. It takes place every 4 to 12 years.
According to the IUCN Red List, the total South American fur seal population size is about 238,000 individuals, including approximately 109,500 mature individuals. Currently this species is classified as Least Concern (LC) and its numbers today increasing.
South American fur seals may have influence on the fish, krill and squid population due to their diet. They are also important as prey for their natural predators (sharks, killer whales).