Californian Sea Lion

Californian sea lion (Zalophus californianus) has a pronounced sexual dimorphism that allows easy identification of individuals: from the sub-adult stage, the male is darker and develops a crest on the skull, which serves as an attraction in the search for a mate, and can weigh up to four times more than the female. Like other subspecies, it emits a loud bark, similar to a lion's roar, both to attract suitors and to keep competitors away.

The Californian sea lion is a social species that lives in large colonies on cliffs, beaches or even man-made piers. The male is very territorial, aggressively defending his harems of up to 20 to 30 females both on land and in underwater areas that he sonorously marks. While the males spend most of their time in the water, the females and juveniles spend most of the year on land, where they give birth to a single calf that they care for between six and twelve months, nursing it with a high-fat milk with hardly any lactose.

Adapted to life in the sea, the Californian sea lion is able to see almost as well in the water as out of it, with vision in the blue and green range of color and a lucid, feline-like mat that reflects light passing through its retina to enhance its vision in low light. It swims at a speed of around 10 km/h and dives for up to three minutes between 20 and 50 meters, although it can dive for up to ten minutes at a depth of 275 meters. Its good eyesight is complemented by a good sense of hearing, superior to that of humans, and it has 38 vibrissae or whiskers on each side of its face with nerves that detect vibrations and provide it with sensory information about its environment.

Studies have found that the Californian sea lion has increased its average body size despite population growth, unlike other subspecies.In the case of females, this is related to a greater variability in the prey on which they feed, while in males, the role of skull size and the strength of neck and jaw muscles in sexual selection has been reinforced in order to compete in courtship for females.

Despite having been important for the subsistence of the indigenous peoples on the coast of California and the islands of the Northern Archipelago, the greatest impact on the species occurred during the 19th and early 20th centuries when it was hunted intensively for its exploitation and even to reduce its impact on fishing. Towards the middle of the last century, the first legislative measures began to be taken in the United States and Mexico for their protection, in addition to the current control of island tourism and the monitoring of the evolution of the populations.

For the Californian sea lion, the only natural predators are killer whales and sharks, as well as coyotes that can attack newborn pups on land. Currently, although the recovery of the species is a fact, its greatest threat is the lack of availability of prey due to hunting or fishing and the pollution of the ecosystems they inhabit, where they are highly exposed to chemicals or heavy metals that easily accumulate in the sea lion's liver and fat.

Both the sea lion and the seal are pinniped species, that is, carnivorous mammals adapted to marine life, characterized by a fish-like body; wide, fin-shaped hind legs and front legs with interdigital membranes, suitable for swimming and diving at high speed; and skin covered with dense fur and abundant fatty tissue underneath to protect their bodies from the cold, store energy and help them float in the sea.

Although sea lions bear a strong physical resemblance to seals, among the characteristics that differentiate them are the following:

• Sea lions have small, somewhat pointed ears, while seals lack an external ear and only two holes are visible on either side of the head.
• Sea lions move on land using their four flippers and can even run, while seals drag their bodies and propel themselves only with their hind legs.
• Sea lions have nails on their hind flippers, which, although they have no function, are maintained from their ancestors more adapted to life on land.