The breeding season for both subspecies of A. pusillus begins in the middle of October. At this time males haul out on shore at the breeding grounds, or rookeries, to establish territories by displays, sparring, or actual battle. They do not eat again until they mate in November or December.
Females come ashore slightly later and also fight amongst each other for smaller territories in which to give birth. Female territories are always within male territories and females who are located on a certain male's territory become part of his harem. While harem sizes of both subspecies can reach as many as 50 females, or cows, the average size of the South African fur seal harem is 28 cows, the Australian fur seal harem averages 10 cows (Schliemann, 1990). Breeding occurs between the male and each of his harem members. While copulation occurs about 6 days after cows give birth to a single pup there is a delay in implantation of the blastocyst. In South African fur seals this delay is approximately 4 months while in Australian fur seals it is about 3 months (Riedman, 1990). Gestation in both subspecies averages 11.75 months (Riedman, 1990).
South African fur seal pups are anywhere from 4.5 to 7 kg and 60-70 cm at birth (King 1983), which occurs in late November or early December. The pups go through two different molts in their first year and a half. Their original coat is black and curly. This coat is replaced between 4 and 5 weeks with an olive-gray coat. The second molt takes place at about 13 months and replaces the olive-gray coat with a silver one which later fades in color (King 1983). Nursing in this subspecies begins immediately after birth and is continuous for the first six days. At this time the mother mates with her male harem leader and then begins going out to sea for food for a few days at a time. By the second month, however, she can be gone for up to two weeks before returning to feed the pup (King, 1983). At four to five months old pups begin supplementing their diet with crustaceans and fish. Lactation does continue, however, until the next pup is born. Pups begin swimming early and continually increase the amount of time that they can spend in the water. At seven months they can swim for two or three days at a time (King, 1983). Females become sexually mature at about 3 years and males may also follow this trend but are unable to establish territory at this time so do not usually mate until several years later (King, 1983).
Australian fur seal pups weigh 4.5 to 12.5 kg and measure 62-80 cm in length at birth. They are a silver-gray in color and their entire ventral side is yellow. Pups in this subspecies are usually born in early to middle December. As in South African fur seals, nursing begins right after birth and is continuous for the first week or so, until the mother mates again and goes out to sea for food. At this time, however, the Australian fur seal returns once every week to feed her pup (Riedman, 1990). By the eighth month of life Australian fur seals are eating some solid supplements although lactation continues until the next pup is born. The pups start swimming for prolonged periods also at the eighth month. Sexual maturity is widely varied within the subspecies. Females reach maturity any time between 3 and 6 years of age (King, 1983). Males probably reach maturity between four and five years of age but cannot hold a harem until they are closer to seven or eight years old (King, 1983).
Average birth mass: 6200 g.
Average gestation period: 368 days.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (male)
Sex: male: 1643 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 1276 days.