Conservation Status– Least Concern
Male California sea lions are a chocolate brown in colour while females are a golden brown colour. After the moult females may appear to be a light grey or silver colour. Most sea lions appear dark brown or black when wet. The chest is lighter in colour.
They have external ear flaps which are quite small. Their front flippers are large allowing them to walk effectively on land. This flipper has bones inside that are same as those in a humans arm. The bones are shorter and the fingers are extended with cartilage. The back flippers are formed with 5 digits like the foot of a human. On the middle three toes are nails.
A small flattened tail sits between the two hind flippers. Male California sea lions have a raised portion of their forehead known as a sagittal crest. This can measure up to 4cm (1.5in) tall. Females have a smooth forehead.
Males are larger typically measuring 2.4m (7.9ft) long. They can weigh up to 350kg (770lb). Females typically reach 1.8 (5.9ft) and weighing up to 100kg (220lb).
The eldest recorded California sea lion in the wild was 17 while in captivity one lived to be 31 years old.
These sea lions are carnivores. They feed on fish, squid, octopus and the occasional clam.
They have a few interesting hunting techniques. One is to follow dolphins and catch some of the fish which they are chasing. Another is to co-operate with dolphins, porpoises and seabirds to hunt a large school of fish.
California sea lions live along the coast of the Americas from British Columbia to Mexico. This includes a number of offshore islands. A colony used to live on the coast of a few Japanese islands but it is now believed this is extinct. The sea lions on the Galapagos islands used to be thought of as a subspecies of California sea lions but are now seen as their own species.
Sandy beaches and rocky areas are the most common homes of California sea lions. Most of the time they are found in the waters of the Pacific Ocean. Increasingly they are making their way into freshwater rivers. They will rest on jetties, piers, buoys and oil platforms where available.
Between May and August the sea lions gather at a rookery where they will breed. Here males establish a territory which they defend for as long as possible. They do not eat during this period living off the blubber. A larger male will be more successful as he can store more blubber. It is very hot during the breeding season so part of the territory always has water for the male to sit in with some even being completely in the water.
Females form a group of 2-20 individuals and begin to move through the territories of the males. Males do not see to work too hard to keep females in their territory and females do not like males to be too energetic or aggressive.
There is a delay between mating and implantation of three months. Following this gestation takes 8 months. They give birth in June or July. A single pup is born at the end of this period. For the first week of their life the mother stays with the pup to nurse it. After this she heads out to sea for up to three days before returning to spend 2-3 days nursing the pup. While they are left on the shore pups form nurseries where they can socialise and play. The mother and pup can find each other on the beach due to their distinct calls.
Weaning age varies greatly in California sea lions. Some wean at 6 months while for others it takes a year. There is believed to be a number of reasons for this. These include food availability, mother’s age, the sex of the pup and if a new pup is born. Females spend more time with the mother before striking out on their own than males do.
Sexual maturity occurs between 4 and 5 years of age though most males cannot hold a territory until they are much older.
Some instances of pups being fostered by other sea lions after they were abandoned have recorded.
California sea lions are highly social. They gather in large groups to rest and will tolerate others lying on them or close to them. In the water they create a raft which a mass of sea lions close together. When it is time to go hunting they form small groups unless they are going after a large number of fish.
When diving they can reach depths of 274m (899ft) and swim at between 15 and 20 miles per hour (24-32 kilometres per hour).
Juvenile and non-breeding California sea lions have been seen engaging in play activities such as surfing, chasing each other, pushing and shoving each other off rocks and mock fights. On occasion adults are seen participating.
Predators of the California sea lion include orcas, great white sharks and bull sharks.
The California sea lion is one of the most vocal mammals. They make barks, growls and grunts.
California sea lions are the ones most commonly seen performing at zoos and aquariums. They are highly intelligent and have been taught to understand a simple version of sign language. Some are even used for military operations.
Top – “Lightmatter seal”. Licensed under CC BY 2.5 via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:Lightmatter_seal.jpg#mediaviewer/File:Lightmatter_seal.jpg
Bottom – By T.Voekler (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons