Otariidae: Sea Lion Family
There are approximately 14 species of fur seal and sea lion. The main features that distinguish these animals from the seals, family Phocidae, are the presence of external ears and their ability to tuck the hind flippers forward to facilitate locomotion on land. Sea lions occur in the southern Atlantic and Indian oceans and in the North and South Pacific, and come to land, or haul out, on coasts and islands.
Generally gregarious, these animals haul out in large numbers at traditional breeding sites, called rookeries, where males compete for the best territories. Males are considerably larger than females, and have big, bulbous heads.
Females give birth to the young conceived the previous year and mate again some days later. Mating and giving birth are synchronized in this convenient manner as a result of the phenomenon of delayed implantation. The embryo lies dormant for a period before development starts, thus ensuring the correct timing of the birth without producing young of undue size.
Australian Sea Lion
Size: 2 - 2.5 m (6.5 - 8.25 ft).
Weight: Up to 300 kg (660 lb).
This species lives around the coast of southern Australia, from Shark Bay in Western Australia to the south-eastern edge of Australia. The Australian sea lion eats fish, squid and crustaceans.
It forms breeding colonies of around 100 individuals on small offshore islands, where dominant males defend small territories centred on females. As well as being strong swimmers, these sea lions are surprisingly adept on land, and can even climb steep cliffs.
South American Sea Lion
South American sea lions do not travel very far from their breeding sites during the non-breeding season, although they may spend long periods out at sea. These sea lions sometimes feed in groups, especially when they are hunting shoals of fish or squid.
Male South American sea lions have dark brown bodies with brown manes on their heads and necks. The females are less heavyset and have paler bodies and no manes.
The breeding season begins at the start of the southern summer. Adults arrive on beaches or flat areas of rock at the beginning of December. Males arrive a few weeks before the females, and defend small patches of the beach. The females give birth to the young they have been carrying since the previous year. After nursing their pups for a few weeks, the females become receptive to mating again. As the number of females increases, males stop controlling territories and begin to defend groups of females. Unsuccessful males without harems of their own gang together on the fringes of the beaches and charge through the females to mate with them.
Distribution: South Pacific and Atlantic waters off the South American coast from northern Peru to Brazil.
Habitat: Coastal waters and beaches.
Food: Fish, squid and crustaceans.
Size: 1.8 - 2.5 m (6 - 8.25 ft); 150 - 350 kg (330 - 770 lb).
Maturity: Females 4 years; males 6 years.
Breeding: Single pup born in January.
Life span: 20 years.
Steller's Sea Lion
Steller’s sea lions live at the coasts of the northern Pacific Ocean, from Japan to California. They prefer cold coastal water, where they feed on fish, squid and octopus. Between hunts, they rest on rocky shores. Adult males are about twice as large as females. Apart from their size, the main difference between the sexes is that males have huge necks, which are made even chunkier by their manes.
Sexually mature sea lions, including pregnant females, gather at breeding grounds in May. Each male defends an area of shore in the hope of encouraging females to give birth there.
Fights between males can be extremely fierce, with the sea lions battering their huge bodies against each other and biting their opponent. The strongest bull is the one with the largest harem of females.
Steller's sea lions are the largest sea lions. Adult males have a distinctive mane that makes them look larger and more impressive, and also provides protection from bites during fights over mates.
After the pups are born (the result of matings the previous year), he will mate with all the females in his territory. The male is not able to feed during the breeding season, because he is always guarding his harem. This fact, combined with the many injuries that males suffer during fights, means that males usually have considerably shorter lifespans than females.
Distribution: Northern Pacific coasts of Canada and the United States to San Miguel Island, California.
Habitat: Rocky shores.
Food: Fish, octopus, squid, bivalve molluscs and crustaceans, occasionally young fur seals, ringed seals and sea otters.
Size: 2.3 - 2.8 m (7.5 - 9.25); 263 - 1000 kg (580 - 2204 lb).
Maturity: 3 - 7 years.
Breeding: Single pup born in summer, usually between late May and early June.
Life span: 20 years.