The South American fur seal breeds between mid-October and mid-January, although the exact timing of births varies between colonies (2) (3) (6) (7). Males are territorial, occupying breeding territories that average around 50 square metres, and driving away rival males with threatening calls and displays. Disputes can escalate into fights, sometimes resulting in serious wounds and scars (2) (3) (6). Successful males will mate with a number of females (6) (9), whereas non-territorial bachelor males will gather on separate beaches where no females are present (3) (9). The female South American fur seal gives birth to a single pup each year, and mates again just a week or so after giving birth. However, the new embryo does not begin development for another three to four months, giving a total gestation period of about a year (3) (4) (6) (7).
After giving birth and then mating again, the female South American fur seal begins to make foraging trips out to sea, alternating these with time spent ashore nursing the pup (8) (9), which is relocated using a combination of vocalisations and scent (3) (9). The pup, which measures around 60 to 65 centimetres at birth (2) (6) (8), is not weaned until around eight months old, although it may continue to suckle for up to two years (3) (6) (7), particularly if conditions have been poor (8). Females will often nurse a newborn at the same time as the previous year’s young (3). When food is scarce, the survival rate of pups may be quite low, and many are also swept away by storms or killed by adult male South American sea lions (Otaria flavescens), or by orcas (Orcinus orca) or sharks (4) (8). Young females usually give birth for the first time at four years old, while males do not mature until around seven years (1) (3) (4) (6), but are unlikely to hold a territory until at least eight years old (8). Female South American fur seals have been recorded living for nearly 30 years (3).
Although the seasonal movements of male and juvenile South American fur seals are not well known, most females remain near the breeding grounds throughout the year (2) (6) (8). The diet of this species includes a variety of fish, crustaceans, cephalopods (such as squid), gastropods and other marine invertebrates (2) (3) (4) (7) (8). Most hunting is done at night (3) (8), and individuals may dive to around 30 metres for up to 3 minutes, although dives to 170 metres for up to 7 minutes have also been recorded (1) (3) (8). At sea, the South American fur seal is often seen travelling or resting in groups, spending much time grooming when resting at the surface (1) (2).