The California Sea Lion (Zalophus Californianus) has three subspecies, namely the California Sea Lion, the Galapagos Sea Lion and the Japanese Sea Lion (presumed extinct) They were hunted extensively for their fur, oil, meat and genitals during the 19th and 20th centuries. They are protected under the US Marine Mammals Protection Act of 1972 and killing of these animals is banned in both Mexico and Canada. Californian Sea Lions are regularly entangled in fishing nets and they continued to be illegally shot by fishermen. The el Nino has also had a devastating impact on the species as has marine pollution in the form of organochlorines such as DDT.
Mating usually takes place between May and July with large adult males arriving first to establish territories. As with other Sea Lions, they can be very aggressive towards each other, engaging in vocal and physical threat displays. Fights are not uncommon.
Females will give birth 4-5 days after coming on shore. Gestation period is around 11 months. Peak birthing tends to be from mid June to mid July. Pups are born measuring +/- 80-90 cm in length and weigh in at around 6-9 kg. Their initial dark brown or black coats are shed after their first month and again some six months later.
The mothers tend to stay with their young for the first week, before leaving to forage. Foraging trips last between 2-4 days, usually within 100 km of the rookery. They return to nurse the pups for 1-2 days before repeating the foraging cycle once more. The nursing period can last between 4-8 months though longer periods of up to a year have been observed.
Approximately one month after giving birth, the females will mate with older bulls. Females, which weigh roughly 85kg and measure 1.8m in length will reach sexual maturity at between 4 and 5 years of age. Males reach sexual maturity at the same age as females, but only get territorial status when they are considerably older, at between 8 and 9 years. Adult males are much larger and measure 2.4m in length and weigh on average 280kg. Their lifespan is around 25 years.
These animals are highly intelligent and have been trained, not only by the captive entertainment industry to perform silly tricks, but also by the US Navy Marine Mammal Program to perform tasks such as mine detection and equipment recovery.
The common “ball balancing” trick employs their whiskers (vibrissae) and not their noses.
Californian Sea Lions are one of the fastest among the pinnipeds, capable of bursts of speed in excess of 40 km/h.
Unlike the other sea lions, this species does not sport the typical mane, though males do have a prominent ‘crest’ on their heads, making them easy to differentiate from females.
When at sea, they may gather together in small groups to float along the surface to rest. They are then referred to as a “raft.”
The deepest dive recorded was over 530m.
U.S. Gillnet fisheries for Halibut and Angel Shark are responsible for the deaths of over 1 000 California Sea Lions each year.
In 1998, several decapitated California Sea Lions, riddled with gunshot wounds, washed up on the beaches near San Francisco.
A number of animals have died due to becoming trapped in the water intake pipes of power plants and accidents with boats are also commonplace.