Zalophus californianus

California sea lions are the best-known eared seals. All seals can hear, but earless seals (in the family Phocidae) have internal ears. The eared seals (sea lions and fur seals, in the family Otariidae) have small external ears. They also can pull their rear flippers up under their bodies and use to them move around on land, which phocids cannot do. California sea lions spend most of their time in coastal waters, and eat fish. Adult males migrate northward for the winter and return to island beaches off the California and Mexican coastlines for the May—July breeding season. They loudly defend patches of territory, on land or in the shallows, fasting for 4—6 weeks while they are on patrol. About a month after pupping (giving birth), females are ready to mate with the males who have been waiting impatiently. Ninety percent of the young are born in June. They are born on land and nurse for a year or more.

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Mammal Species of the World

The California sea lion is a highly gregarious species, hauling out in large groups, although tending to feed individually or in small groups, unless large quantities of food are present. They feed on a large number of different fish species (including some commercial species), such as northern anchovies, pacific whiting, mackerel and are known to also take some cephalopod species. Dives usually last about two minutes, but can last up to ten minutes, and average depths of 26 to 98 metres, although California sea lions have been known to dive to well below 200 metres (2). The breeding season starts in May, at which time adult males begin to fight for a territory. Most males are unsuccessful and retreat to the sea, or to bachelor beaches nearby. Successful males guard their territory and maintain boundaries with routine displays and frequent barking. A male may maintain his territory for up to 45 days depending on other competitive males and on fat reserves. Females give birth to a single pup throughout May and June and are ready to mate again about 28 days after giving birth, although this interval is more variable among the population in Mexico. The mothers spend the first week after birth with their pup and then begin alternating feeding trips at sea (two to three days) with suckling bouts on land (one to two days), until the pup is weaned, at about ten to twelve months. The mothers and pups recognise each other after separation by sound and smell (2). The breeding season ends in August after which time most males migrate north and the females and juveniles disperse, but stay close to the breeding islands. Average lifespan is 15 to 24 years with the young reaching sexual maturity at about four to five years. However, males will generally fail to hold a territory until they are older (2).

This highly social and intelligent species is well adapted to a semi-aquatic life-style. California sea lions swim using their fore-flippers and are particularly agile on land as they are able to control their hind flippers independently (3). Male and female California sea lions differ significantly in appearance. Males are substantially bigger than females and have an enlarged sagittal crest, which is usually topped with white fur. The adult males are generally dark brown with a lighter belly and side colouring, whereas the females can appear more tan coloured. The pups are born with a blackish-brown coat which moults after a month and is replaced with a light brown coat. This coat is shed after four or five months and replaced with the adult coat. The California sea lions found in Mexico appear smaller than those found in California (2).

The California Sea Lion occurs in the eastern North Pacific from Islas Tres Marias north of Puerto Vallarta, north throughout the Gulf of California and around the end of the Baja California Peninsula north to the Gulf of Alaska. Sightings of vagrants have been reported from the southern Bering Sea in the north (Maniscalco et al., 2004) to Chiapas Mexico in the south. Females, which were only very rarely found north of Point Conception in the early 1980s, are now routinely found in northern California, where former breeding sites have been reoccupied.

Large numbers of adult and subadult males and juveniles undertake a post-breeding season migration north from the major rookeries in southern California and Baja California and winter from central California to Washington State. Smaller numbers of animals migrate to British Columbia and southeast Alaska, making it to the northern Gulf of Alaska, Alaska Peninsula, and eastern Aleutian Islands. Other animals appear to remain in the Gulf of California year round and do not undertake long migrations.

Zalophus californianus are found along the shore from California to Mexico including Baja and Tres Marias Islands, in the Galapagos Islands and in the southern Sea of Japan (Scheffer, 1958). The populations in each area do not interact with other populations (Scheffer, 1958) and therefore are considered subspecies. California sea lions tend to seasonally migrate long distances (Riedman, 1990). Males usually migrate north to British Columbia after the breeding season (Mate, 1978).

Biogeographic Regions: nearctic (Native ); pacific ocean (Native )

East North Pacific, Gulf of Mexico

occurs (regularly, as a native taxon) in multiple nations

Global Range: Coastal North Pacific, Mazatlan and Baja California to Vancouver Island (males in fall and winter); breeds on San Miguel, San Nicolas, Santa Barbara, and San Clemente islands in southern California; largest breeding colony is on San Miguel Island; a few pups are born occasionally at South Farallon and Ano Nuevo islands off central California; in Mexico, breeds on the Coronados, Guadalupe, San Martin, Cedros, and San Benito islands off the Pacific coast of Baja California, and there are many smaller colonies on islands in the Gulf of California (Keith et al. 1984, Reeves et al. 1992). Galapagos and eastern Asian populations, sometimes included in this species, are now regarded as distinct species.

Found from British Columbia in Canada south to Baja in Mexico, including the Gulf of California. California sea lions breed mainly on offshore islands from southern California's Channel Islands south to Mexico (4).

Newborn pups average 75 cm in length and weigh between 5 to 6 kg. Adult males average 2.2 meters in length and 275 kg in weight but can reach length of 2.4 meters and weights of 390kg. Females are smaller, averaging 1.8 meters in length and 91 kg in weight but can reach lengths of 2 meters and weights of 110kg . Pups have a blackish brown coat, which is molted by the first month and replaced with a light brown coat. The light brown coat is shed after 4 or 5 months and replaced with the adult pelage. Adult males are mostly dark brown with lighter belly and side coloring. Adult females are dark brown but can also appear tan. Zalophus californianus exhibit pronounced sexual dimorphism . Adult males have an enlarged saggital crest and a lighter pelage. In addition to the head features males are more robust and larger than females. All California sea lions have black flippers which are coated with short black stubble. The typical dental formula is 3/2, 1/1, and 5/5.

(Mate, 1979,)(Jefferson et al., 1993), and (Riedman, 1990)

Range mass: 390 (high) kg.

Range length: 2.4 (high) m.

Other Physical Features: endothermic ; bilateral symmetry

Length: 250 cm

Weight: 300000 grams

Sexual Dimorphism: Males are about four times larger than females.

Length:
Average: 2.1 m males; 1.6 m females
Range: 2-2.5 m males; 1.6-1.8 m females

Weight:
Average: 375 kg males; 94 kg females
Range: 350-400 kg males; 90-120 kg females

Habitat and Ecology

Systems

• Terrestrial
• Marine

Zalophus californianus generally live along coastlines but have been found in rivers in along the northern Pacific coast. California sea lions often congregate on man-made structures such as jetties, piers, offshore buoys and oil platforms. Zalophus californianus tend to inhabit places which have undergone human intervention (Riedman, 1990).

Habitat Regions: temperate ; saltwater or marine

Aquatic Biomes: rivers and streams; coastal

Depth range based on 6192 specimens in 1 taxon.
Water temperature and chemistry ranges based on 2769 samples.

Environmental ranges
  Depth range (m): 0 - 139.2
  Temperature range (°C): 8.622 - 26.131
  Nitrate (umol/L): 0.038 - 26.169
  Salinity (PPS): 30.381 - 35.304
  Oxygen (ml/l): 2.414 - 6.583
  Phosphate (umol/l): 0.330 - 2.161
  Silicate (umol/l): 1.436 - 34.422

Graphical representation

Depth range (m): 0 - 139.2

Temperature range (°C): 8.622 - 26.131

Nitrate (umol/L): 0.038 - 26.169

Salinity (PPS): 30.381 - 35.304

Oxygen (ml/l): 2.414 - 6.583

Phosphate (umol/l): 0.330 - 2.161

Silicate (umol/l): 1.436 - 34.422
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Habitat Type: Marine

Comments: Coastal waters. Hauls out on rocky and sandy beaches, primarily on islands. Young are born in rookeries on rocky and sandy beaches, primarily on islands.

Breeding occurs on sandy beaches and rocky areas of remote islands where there is easy access to shade, water for cooling down and plenty of food (2). California sea lions generally fish in open waters along the Pacific coast, but are increasingly being found up rivers and often congregate on man-made structures such as jetties and piers (5).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

After the breeding season (August-September) some adult and subadult males move northward and overwinter as far north as British Columbia; return south March-May. Males from Baja California rookeries arrive in southern California in December-January (Reeves et al. 1992). Migratory status of females and young unclear.

Male California sea lions have been known to assemble at the mouths of fresh water rivers where there is a steady supply of fish. California sea lions tend to feed alone or in small groups unless there is an large quantity of food. Under conditions of increased food supply, Z. californianus hunt in larger groups. Zalophus californianus have been known to feed cooperatively with cetaceans, seabirds and harbor porpoises. Often one species locates a school of fish and signals the presence of food to the other species. While rare, it has been recorded that California sea lions drink seawater while not breeding (Riedman, 1990).

Foods eaten include: cephalopods, anchovies, herring, Pacific whiting, rockfish, hake, salmon, squid and octopuses (Riedman, 1990).

Animal Foods: fish; mollusks

Primary Diet: carnivore (Piscivore , Molluscivore )

Comments: Opportunistic feeder. Feeds on squid, octopus, and a various fishes, including herring, anchovy, whiting, mackerel, sardines, hake, rock-fish, etc. Males do not feed during breeding season. Lactating females at San Miguel Island forage with 100 km of rookery, in highly productive upwelling areas; most feeding dives are relatively shallow (26-74 m) (Reeves et al. 1992).

See Riedman, 1990.

Known Predators:

• great white sharks (Carcharodon carcharias)
• bull sharks (Carcharhinus leucas)
• killer whales (Orcinus orca)

Zalophus californianus is prey of:
Carcharodon carcharias
Carcharhinus leucas
Orcinus orca

This list may not be complete but is based on published studies.

Zalophus californianus preys on:
Cephalopoda
Genyonemus lineatus
Trachurus symmetricus
Engraulis mordax
Actinopterygii
Mollusca
Enhydra lutris

Based on studies in:
USA: California, Southern California (Marine, Sublittoral)

This list may not be complete but is based on published studies.

10,000 to >1,000,000 individuals

Comments: U.S. population was estimated at more than 160,000 in the mid-1990s (NMFS, Federal Register, 15 March 1996).

Gregarious at all seasons. Predators include killer whales and sharks, though these have little impact on populations.

Comments: Feeds mostly at night, spends the morning and mid-day sleeping on beaches.

The oldest recorded wild Z. californianus lived 17 years (Mate, 1979).

In captivity, the oldest recorded Z. californianus lived to be 31 years old. The age of Z. californianus can be determined by counting the number of rings on cross sections of its teeth (Mate, 1978).

Range lifespan
Status: wild: 17 (high) years.

Range lifespan
Status: captivity: 31 (high) years.

Average lifespan
Status: wild: 17.0 years.

Average lifespan
Status: captivity: 30.0 years.

Maximum longevity: 35.7 years (captivity) Observations: The total gestation time, of approximately 11.5 months, probably includes a 3 month period of delayed implantation (Ronald Nowak 2003). In the wild, these animals appear to live up to 17 years (Bernhard Grzimek 1990). One wild born male was still alive in captivity at about 35.7 years of age (Richard Weigl 2005).

During breeding season males claim territories. A male consistently occupies a territory until factors change and cause him to be displaced. Typical occupation time is approximately two weeks; few Z. californianus males remain at their site for longer. While guarding their territory, males remain present and do not leave even in pursuit of food. As external factors change, males replace other males on the territory. Replacement occurs throughout the entire breeding season. Males are known to attack if others invade their territory. California sea lions tend to breed on islands or remote beaches. Zalophus californianus exhibit moderate to extreme polygyny and tend to live in colonies of a few males and many females. Female Z. californianus exhibit mate choice, by "respond[ing] differently to the attempts of various males"(Riedman, 1990).

Mating System: polygynous

The peak breeding season occurs in early July. The total gestation period is about 11 months (Riedman, 1990). Most births occur from mid-May to mid-June (Scheffer, 1958) with the majority of pups born in mid-June. The time between birth and estrus is about 28 days. California sea lions reach sexual maturity between four and five years (Riedman, 1990).

Breeding season: mating in July, births in mid-May to mid-June

Average number of offspring: 1.

Average gestation period: 11 months.

Range weaning age: 6 to 12 months.

Average age at sexual or reproductive maturity (female): 4-5 years.

Average age at sexual or reproductive maturity (male): 4-5 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal )

Average birth mass: 7000 g.

Average gestation period: 259 days.

Average number of offspring: 1.2.

Average age at sexual or reproductive maturity (male)
Sex: male: 1826 days.

Average age at sexual or reproductive maturity (female)
Sex: female: 1095 days.

The lactation period in Z. californianus ranges from six months to a year. There are many possible reasons for the variation in lactation periods including availability of food resources, the mother's age and health, the sex of the pup and the birth of a new pup. Zalophus californianus provide more lengthy maternal care for female offspring then for male offspring, yet during lactation both males and females have equal access and receive equal resources.

Parental Investment: female parental care

Males establish breeding territories after arrival of females. Single pups are born mainly in late June in California, late May-January in Galapagos. Females mate 3-4 weeks after giving birth, then make periodic trips to sea to feed. Young are weaned generally in 4-8 months in California but frequently after more than a year and sometimes three years in the Galapagos. Females sexually mature at about 4 years, may live up to 25 years; most adult females breed annually. Males first breed probably at 9-10 years.

The following is a representative barcode sequence, the centroid of all available sequences for this species.

There are 2 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 2
Specimens with Barcodes: 5
Species With Barcodes: 1

Canada

Rounded National Status Rank: N5N - Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

Year Assessed

Assessor/s

Reviewer/s

Justification

History

• 1996
  Lower Risk/least concern

Zalophus californianus are well protected in most areas. Occasionally, they are trapped with a permit for display in zoos, aquariums, and circuses (Mate, 1979). In Mexico, a few California sea lions are trapped each year, while in the United States they are fully protected under the Marine Mammal Protection Act.

Occasionally California sea lions pose a problem for fishermen by stealing fish from commercial fishermen netting. A significant number of California sea lions have been killed as a result of getting tangled in discarded fishing gear. (Riedman, 1990). From 1983 to 1984, Z. californianus experienced a decline of 60 percent in pup production from previous years. Also during this time food resources declined, which led to inhibited growth and increased mortality. During this time mothers left their pups earlier in search of food, which truncated the lactation period, thus reducing the amount of nutrients a pup received and making it more susceptible to death.

According to IUCN, the following subspecies are recognized:

Zalophus californianus ssp. japonicus (extinct)

Zalophus californianus ssp. wollebaeki (vulnerable)

Zalophus californianus ssp. californianus (no special status).

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Rounded Global Status Rank: G5 - Secure

Classified as Least Concern (LC) on the IUCN Red List (1).

Population

Population Trend

Global Short Term Trend: Increase of 10 to >25%

Comments: Numbers have increased in southwestern Canada since the early 1970s (Bigg 1988). Total U.S. population increased steadily over the past two decades (NMFS, Federal Register, 15 March 1996). The number of pups born in the Channel Islands increased from about 19,000 in 1989 to 25,000 in 1990 and 31,000 in 1991 (Reeves et al. 1992).

Major Threats

Comments: In the early 1980s, as many as 1500/year may have died as a result of entanglement in gill nets or from being shot by commercial fishermen; such mortality continues at an unknown rate. In the late 1960s and early 1970s, premature births were observed in California, evidently the result of DDT and PCB contamination and viral and bacterial infections (Reeves et al. 1992).

The California sea lion faces a number of threats, most notably through human-animal conflict and climate change. In the 19th and early 20th centuries California sea lions were extensively killed for commercial purposes, and although later afforded some protection, were still killed in large numbers until hunting was banned between 1969 and 1972. Population numbers have now recovered, but growing numbers are being killed in fishing nets. California sea lions are also increasingly thought to be damaging commercial fish stocks and in 1999 the federal National Marine Fisheries Service released a report recommending that Congress allow wildlife managers to kill California sea lions that are preying on endangered fish species (6). California sea lions are also negatively affected byEl Niño, which causes a shortage in food supply and increased mortality (2). Other causes of mortality include infection, disease, poisoning, pollution and toxic phytoplankton blooms (2) (6).

Conservation Actions

The California sea lion is currently classified as Lower Risk / Least Concern on the IUCN Red List and at present the population is quite capable of recovering from limited conflict with humans and the occasional El Niño event. As long as there is enough food, and some level of protection remains, it is thought that there is no immediate threat to the survival of the California sea lion. The extinction of the Japanese sea lion, however, reminds us that there can be limits to the recovery of populations from high mortality, especially for the smaller population in Mexico, where human interaction combined with natural stress may make recovery more difficult (2).

California sea lions are thought by some to seriously reduce stocks of commercially-valuable fish such as salmon. They also may interfere with nets used by fishermen.

Negative Impacts: crop pest

Zalophus californianus used to be hunted for their hides and for animal food. California sea lions are also used by the U.S. Navy for retrieval programs, including search and rescue and retrieval of military hardware. They are also used to patrol areas in search of threats. California sea lions are widely used in educational programs throughout the world because of their agility and trainability. They are charming ambassadors for their sea lion cousins.

Positive Impacts: ecotourism ; research and education

Comments: Widely displayed in zoos, aquaria, and circuses.

With increasing populations in southwestern Canada, there have been increased complaints from fisherman about interference with fishing operations and damage to gear and stocks of herring, squid, and cod (Bigg 1988). At Chittendon Locks near Seattle, Washington, since the 1980s, adult males have been a problem by preying on already depleted steelhead populations. Success of translocations of "problem" sea lions preying on steelhead near Seattle, Washington, has been limited by the return of some of the translocated individuals, from release points as far as southern California (Reeves et al. 1992).

See Reeves et al. (1992) for history of exploitation.