The Galapagos sea lion is essentially a coastal animal and is rarely found more than 16 kilometres out to sea (2). Individuals are active during the day and hunt in relatively shallow waters (up to about 200 metres deep) where they feed on fish, octopus, and crustaceans. Sea lions and seals are also capable of making extraordinarily deep dives of up to 200 metres for 20 minutes or more, then rapidly surfacing with no ill effects (5). When ashore, the Galapagos sea lions rest on sandy beaches and rocky areas in colonies of about 30 individuals (2). They are extremely gregarious and pack together on the shore even when space is available (2).
Each colony is dominated by one bull that aggressively defends his territory from invading bachelor males (5). This territorial activity occurs throughout the year and males hold their territories for only 27 days or so before being displaced by another male (2). Within this territory the bull has dominance over a group of between 5 and 25 cows. The breeding season is not dependant on migration patterns, as seen in other sea lion species, since the Galapagos sea lion remains around the Galapagos Archipelago all year round. In fact the breeding season is thought to vary from year to year in its onset and duration, though it usually lasts 16 to 40 weeks between June and December (2). Births therefore also take place throughout the year, with females coming ashore to give birth to a single pup. Within two to three weeks of giving birth females go into oestrous again and actively solicit a male (2). Gestation lasts around 11 months, though it probably includes a three month period in which implantation of the fertilised egg is delayed while the female nurses her young (2).
Like other sea lions this species relies on cooperation within the group. Often, a single adult female will watch over a group of young pups while other mothers are fishing. They are careful to keep the young pups out of deep water where they may be eaten by sharks (6). The bull will also watch out for his "family" by warning them of the presence of a nearby shark with barks, and even occasionally chasing away the intruder (7).