Steller's sea lions breed in massive, noisy rookeries common to most members of this family (4). The males arrive at the haul-out sites in spring and establish their territory on the limited space of the beach; they usually do not feed throughout the breeding season, as they cannot afford to relinquish their hard-won position (7) (8). Females arrive in mid-May to late June and give birth to a single pup; only four days later the female is ready to mate again and the most successful males will aggressively guard, and mate with, up to 30 females (9). Despite mating straight after giving birth, the fertilised egg will not be implanted into the female's uterus until October (3). Both males and females reach sexual maturity at around three to six years of age, but males are unlikely to breed successfully until their eighth to tenth year due to the fierce competition at rookeries (3). Around nine days after giving birth the female will resume foraging trips to the sea. Most pups are weaned when about one year old, but a mother may continue to suckle her young for up to two or three years (6). The breeding season draws to an end in early July but these sea lions maintain their social lifestyle, being commonly seen on shore throughout the year in groups of tens to hundreds of animals (4) (7). Steller's sea lions are opportunistic hunters, feeding on a wide range of fish and cephalopods such as squid (6). In Alaska some of the more important prey species are walleye pollock (Theragra chalcogramma), Atka mackerel (Pleurogrammus monopterygius) and Pacific herring (Clupea harengus) (6).