California Sea Lion (Zalophus californianus): Facts and Habitat

What does a California sea lion look like?

California sea lions belong to the eared seals (family Otariidae), the group that also includes the fur seals. Unlike true seals, they have small external ear flaps, long, strong front flippers that they use like wings to “fly” through the water, and hind flippers that can rotate forward under the body. That lets them walk, run and even climb on land on all four flippers, while a true seal such as the harbor seal has to wriggle on its belly. The differences are set out in seal vs sea lion.

Females and young sea lions are slender and golden brown to tan, looking darker when wet. Adult males are much bulkier, with a thick neck and chest and a dark brown to almost black coat. From about 4–5 years of age, males develop a raised bony crest on the top of the head, giving them a high, domed forehead that is often topped with paler, tan or blond fur. Pups are born with a dark brown to black coat that they molt at about 4–5 months old. All have a long, narrow snout, large dark eyes and long, sensitive whiskers.

How big is a California sea lion?

The California sea lion shows strong sexual dimorphism, meaning males and females differ greatly in size.

Males can weigh three or four times as much as females. Their extra size helps them win and hold breeding territories, and their blubber lets them fast for weeks while they guard those territories.

Where do California sea lions live?

California sea lions live along the Pacific coast of North America, from southeast Alaska and British Columbia south to central Mexico, including the Gulf of California. Most breeding takes place on islands: in the United States mainly on California’s Channel Islands, such as San Miguel and San Nicolas, and in Mexico on islands off Baja California and in the Gulf of California.

After the breeding season, many adult and young males migrate north to feed off central and northern California, Oregon, Washington, British Columbia and southeast Alaska. Females and pups mostly stay closer to the breeding colonies. Sea lions in the Gulf of California do not migrate.

They haul out, or come ashore to rest, on sandy beaches, rocky shores and islands, and readily use human structures such as jetties, marina docks and navigation buoys. They sometimes travel up rivers too, for example about 235 km (146 mi) up the Columbia River to Bonneville Dam.

What do California sea lions eat?

California sea lions are carnivores that eat a wide variety of fish and cephalopods, mainly what is plentiful nearby. Common prey includes market squid, octopus, northern anchovy, Pacific sardine, mackerel, rockfish, Pacific hake (whiting), herring and salmon. They usually hunt in coastal waters over the continental shelf, sometimes near the seafloor.

They can feed alone or in groups, and big schools of fish may draw hundreds of sea lions together, often alongside dolphins, porpoises and seabirds. Most dives last less than 3 minutes and go no deeper than about 80 m (260 ft), but sea lions have been recorded diving to about 274 m (900 ft) and staying down for about 10 minutes. They cruise at about 11 km/h (7 mph), with faster bursts when chasing prey, and often leap clear of the water, a behavior called porpoising, when traveling quickly.

Their adaptable diet sometimes brings them into conflict with people. Some learn to take fish from fishing lines and nets, and some gather below dams and fish ladders, where salmon and steelhead crowd together.

Behavior and communication

California sea lions are very social. On land they often pile together in tight groups, and at sea they may rest in rafts. A common sight is a sea lion floating with one or more flippers held up out of the water. This “rafting” helps them control body temperature, warming or cooling the flippers in the air, and is not a sign of trouble.

They are among the noisiest marine mammals. Territorial males bark almost constantly during the breeding season, and mothers and pups recognize each other by their calls. The reasons behind all that noise are explained in Why do sea lions bark?

Young sea lions are famously playful. They chase each other, toss objects such as kelp, ride waves and play-fight, behavior that helps them practice skills they will need as adults.

Breeding and pups

The breeding season runs from about May to August. Large males set up territories on the beach or in the shallows and defend them with barking, head-shaking, staring and lunging displays, and sometimes real fights. A male may hold a territory that includes up to about 14 females for a few weeks, fasting the whole time. Males can breed at about 4–5 years old but usually cannot hold a territory until about 9–12 years.

Most pups are born in June. Females mate again about 3–4 weeks after giving birth, but the embryo does not implant in the womb for about three months, a process called delayed implantation, so the next pup arrives about a year later.

For about the first week to 10 days, the mother stays with her newborn. After that she alternates trips to sea of about 2–5 days with 1–2 days ashore nursing. Pups left behind gather in groups to rest and play. When she returns, the mother calls, the pup answers, and she confirms its identity by smell. Pups usually nurse for most of their first year, and some keep suckling into a second year.

How smart are California sea lions?

California sea lions are among the most studied marine mammals for learning and memory. Researchers led by Ronald Schusterman in California taught sea lions to follow simple gesture-based “sentences” and to group symbols into categories. One sea lion, named Rio, still remembered a learned matching rule about 10 years after her last practice. In a study published in 2013, another sea lion, Ronan, learned to bob her head in time to music, something once thought possible only for animals that can imitate sounds, such as humans and parrots. See how they compare with other species in our list of the smartest animals.

Their intelligence and trainability explain why they are familiar in zoos and aquariums. The US Navy Marine Mammal Program has also trained California sea lions to find and mark objects on the seafloor and to detect swimmers near ships and harbors.

Predators and threats

The main natural predators of California sea lions are orcas and great white sharks. Sharks usually ambush sea lions resting at the surface, and many survivors carry scars on their hindquarters.

Today’s biggest threats come from people and a changing ocean:

• Toxic algae. Blooms of the diatom Pseudo-nitzschia produce domoic acid, a toxin that builds up in anchovies and sardines. Poisoned sea lions can suffer seizures, disorientation and brain damage, and many die. The toxin was first identified as a cause of mass sea lion deaths in central California in 1998, and severe outbreaks have followed since, including a major event off Southern California in 2023.
• Warm-water years. During marine heatwaves and El Niño events, prey moves away from the breeding islands. Between 2013 and 2016, thousands of starving pups stranded on California beaches.
• Entanglement. Sea lions get caught in fishing nets, lines, packing bands and other debris, which can cut into their necks.
• Conflict. Some are shot illegally by people angry about lost fish, and individual sea lions that eat endangered salmon at Columbia River dams have been removed under federal permits since 2008.

Conservation status

The IUCN Red List lists the California sea lion as Least Concern, with an increasing population. Hunting for hides, oil and animal food once reduced its numbers, but since the US Marine Mammal Protection Act of 1972 made it illegal to hunt, kill, capture or harass marine mammals, the US population has grown strongly, at up to about 7% a year between 1975 and 2014. NOAA estimates the US stock at roughly a quarter of a million animals, close to what the coast can support. Populations in Mexico are smaller, and the Gulf of California population has declined.

Two close relatives were once treated as subspecies. The Galápagos sea lion is now considered a separate species, and the Japanese sea lion, the third member of the genus Zalophus, became extinct in the 20th century.

Sea lions and people

Because they are common, bold and easy to watch, California sea lions are one of the best-known marine mammals in North America. The colony on the floating docks at San Francisco’s Pier 39 attracts huge crowds, and its story is told in Why are there sea lions at Pier 39?

Sea lions are usually not aggressive, but large males can bite, especially when people get too close or feed them. NOAA asks people to stay at least 50 yards (46 m) away, and feeding wild sea lions is illegal in the United States. A pup alone on a beach is usually waiting for its mother, so it should be left alone and reported to a local marine mammal stranding network if it looks sick or injured. The risks are explained in Are sea lions dangerous?