Steller Sea Lion Eumetopias jubatus

Steller Sea Lion Behaviour

Steller Sea Lion Breeding Behaviour

Steller sea lions historically bred on offshore islands from California to Russia. They no longer breed in California. Pups are born black or dark brown in colour which they carry for about four months when they molt into a lighter brown pelage. Gradually over three years, successive molts make them adult colored. Females provide milk to their pups which they locate by their calls and smells amidst the melee of a breeding rookery. Molting by the adults occurs in late summer and can last for several months. Females and males become sexually mature at about 3 to 8 years of age although males do not have the size and stamina to defend a territory until they are about 9 years old (Wilson and Ruff 1999). The wear and tear of defending a territory takes a toll – males seldom live beyond their teenage years. Males defend territories in May when receptive females arrive at breeding islands. Mating occurs mostly on land and birthing from the previous year’s matings occurs in late May through July. Single pups are the norm although twins rarely occur. Pups are nursed during the day and abandoned at night when mothers depart on foraging trips. Weaning occurs about a year later (Wilson and Ruff 1999).

 Steller Sea Lion Feeding Behaviour

Sea lions feed mostly at night and haul out on rocky reefs, points and logs booms during the day. The Steller sea lion is known to eat 50 species of fish and invertebrates including bottom fish and salmon (reviewed by COSEWIC 2005) and they are attracted to areas when eulachon and herring spawn (Womble et al. 2005) including the mouth of the Fraser River (Bigg 1985, Bigg et al. 1990). They catch and swallow fish during shallow dives of about 20 meters but sea lions can reach 200 meters depth (Reeves et al. 2002). Large fish requiring handling are sometimes brought to the surface where they are torn into pieces that can be swallowed. Diet studies are ongoing in Alaska to understand if the diet is affecting the species survival and reproduction. Walleye Pollock is often eaten in Alaska by sea lions whereas herring, rockfish, cod, octopus and squid are eaten in British Columbia.