California Sea Lion

Common Name: California Sea Lion

Class: Mammalia

Order: Pinnipedia

Family: Otariidae

Genus: Zalophus

Species: Zalophus californianus

 

Taxonomy/Description

California Sea Lions belong to the Mammalian Order Pinnipedia, in the family Otariidae.  Other members of Otariidae include all species of fur seals and sea lions.  Otariids are easily distinguishable from other pinnipeds by their external ear flaps.  The California Sea Lion's scientific name is Zalophus californianus, which means "large crest belonging to California".  "Large crest" refers to the very prominent sagittal crest present on male sea lions.

When sea lions are born they are almost black in color.  But adults can be almost any shade of brown ranging all the way to a very light tan.  Sea lions, like other eared seals, are very sexually dimorphic.  This means that it is very easy to distinguish adult males from females.  For one thing, males tend to be much larger in overall size than females.  Males may weigh as much as 1000lbs, with females can reaching 300lbs.  Adult males are distinguished by the pronounced sagittal crest on their skulls.  This gives the appearance of a "bump" on the top of their head.  Females also tend to be lighter in color.  California sea lions live to about 25 years of age.

Habitat/Diet

Their range spans the Pacific coast, from British Columbia to northern Mexico.  Subspecies inhabit the Galapagos Islands and coastal Japan.  The diet of sea lions is quite varied.  They are opportunistic feeders that will mainly eat fish.  Other small marine creatures like lobster , squid, octopi, crabs, clams, crustaceans, and mollusks are eaten when available.  California sea lions are capable of reaching speeds of 15 to 20 miles per hour, dive up to 450ft, and stay submerged 20 minutes to hunt for prey.  Their whiskers, called vibrissae, detect vibrations in the water from prey species. 

Behavior/Reproduction

Sea lions, like other pinnipeds, have an amazing feature that helps them to thermoregulate.  They have have special shunts within their bodies called AVA's (arterio-venal anastomosis) which assists them in regulating their body temperatures.  Depending on their surroundings and on whether they feel too cold or too warm, they can alternatively reduce their blood flow to their skin or increase it significantly.  For example, on a deep dive into cold water a sea lion will conserve its heat by closing down the blood vessels leading to its flippers so that most of its blood is kept under the blubber of its main body.  Alternatively, on a warm day, a sea lion may greatly dilate those same blood vessels and float along with its flippers in the air as its skin soaks up the heat from the sun's rays.  They bask in the sun during the day and feed at night.

Colonies may reach numbers of 1,000 or more individuals.  At breeding season, males will come ashore to the beaches first and battle with each other for territories.  When the females come ashore later, they favor the males that have obtained the best territories and in this way harems develop with about sixteen females for every territorial male.  Ritualized fighting and large size is the key to reproductive success among male sea lions and this is undoubtedly what has led to the extreme sexual dimorphism in this species.

Most pups are born in June or July and nurse for at least six months or more.  A mother will give birth to only one pup.  Mother and pups recognize each other by vocalizations, sight, and smell.  They are hunted by killer whales, sharks and humans.

Sea lions are very beautiful, intelligent and playful.  In the wild, we saw them deliberately allowing themselves to get knocked around in the waves and playing "king of the mountain" on cliffs.  Because of their adaptive natures and their playfulness, they are often included in zoos and aquariums around the world where they are trained to perform various behaviors in shows and demonstrations. 

 

Conservation

Their population is growing and is now at approximately 200,000, but even though they are protected by law, they are still threatened by over fishing, fishing nets, and water pollution.  One example of sea lions and humans living side by side takes place in San Francisco, California.  A colony of California sea lions lives on Pier 39, a dock right next to San Francisco's boardwalk!  Here tourists and conservationists can view these amazing creatures in a place chosen by the sea lions

 

Content provided by Canisius College students under the direction of Michael Noonan, PhD.