|Scientific Name:||Zalophus californianus (Lesson, 1828)|
Zalophus californianus ssp. californianus (Lesson, 1828)
|Taxonomic Notes:||California Sea Lions were once considered a subspecies of Zalophus californianus (Z. c. californianus) by many authors, but Rice (1998) argued that Z. californianus, Z. japonicus, and Z. wollebaeki are distinct species. Other studies have confirmed the separate species status of Z. japonicus and Z. californianus (Brunner 2004, Sakahira and Niimi 2007) and the separation of Z. californianus and Z. wollebaeki (Wolf et al. 2007).|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Aurioles-Gamboa, D. & Hernández-Camacho, J.|
|Facilitator/Compiler(s):||Lowry, L., Ahonen, H., Pollock, C.M., Chiozza, F. & Battistoni, A.|
California Sea Lions have recovered from historical exploitation and their population is now large and still expanding slowly. Beyond the temporal effects of El Niño events, no other major threats are apparent. They should be listed by IUCN as of Least Concern.
|Previously published Red List assessments:|
|Range Description:||California Sea Lion rookeries are found on islands from Los Islotes in Baja California Sur to the Channel Islands in southern California. Some pups have been reported from Año Nuevo Island and the Farallon Islands in central California (Keith et al. 1984). In addition to rookeries, this species also occupies haul-out sites, mainly during the fall and winter when predominately adult and sub-adult males move north to Oregon (USA) and British Columbia (Canada; Fry 1939, Mate 1975, Odell 1975). In the southern part of their range, haul-out areas are known to occur on islets off the coast of Mazatlán and the Islas Tres Marias north of Puerto Vallarta; however, this area has not been surveyed for decades. This species’ overall range extends north through the Gulf of Alaska as far as the Aleutian Islands (Maniscalco et al. 2004), and south around the end of the Baja California Peninsula to the Gulf of California. Between 2005 and 2013, several California Sea Lion sightings were reported as far south as Punta San Pedrillo, Costa Rica (Lenin Oviedo pers. comm.). A California Sea Lion male was sighted off the coast of the Yamsky Islands in the Shelikova Bay in the Sea of Okhotsk in 2007, 2008 and 2011. On each occasion, the animal was seen with a group of Steller Sea Lions. It was not observed during 2013 and 2014 (Vladimir Burkanov pers. comm.). Females, which were only very rarely found north of Point Conception, California in the early 1980s, are now routinely found in northern California, where former breeding sites have been reoccupied. However, adult female California Sea Lions tend to reside at their rookeries (Hernández-Camacho et al. 2008a). Based on estimates of sex biases in gene flow, females disperse on average 6.75 times less frequently than their male counterparts (González-Suarez et al. 2009).|
Native:Canada; Mexico; United States
Vagrant:Costa Rica; El Salvador; Guatemala; Honduras
|FAO Marine Fishing Areas:|
Pacific – eastern central; Pacific – northeast
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Exploitation during the 19th and 20th centuries reduced the California Sea Lion population, but not as much as some other pinniped species (Gerber and Hilborn 2001). Odell (1971) estimated the size of the breeding population on the California Channel Islands to be approximately 35,000 in 1964. Since then the population size has increased considerably.|
Five geographic populations have been identified based on mitochondrial DNA: 1) Pacific temperate, from California to northern Baja California; 2) Pacific subtropical, along the west coast of Baja California; 3) southern Gulf of California; 4) central Gulf of California; and 5) northern Gulf of California (Schramm et al. 2009). Using both nuclear and mitochondrial DNA, the population structure in Mexico suggests a pattern of isolation by distance resulting in at least three management units: the Pacific coast of Baja California, the southern Gulf of California, and the north-central Gulf of California (González-Suárez et al. 2009). The species does not show signs of a reduction in genetic variability (González-Suarez et al. 2009, Schramm et al. 2009, González-Suarez et al. 2010).
It is not possible to directly count individuals in order to obtain the total population size because not all age- and sex-classes are on shore at the same time. Therefore, the size of the population is estimated based on the number of births and the proportion of pups in the population following the methods developed by Boveng (1998) and Lowry et al. (1992). Pups are the only age class constantly on land during the reproductive season, and thus they are used as a reference point in estimating the other age classes. The 2007 minimum population on the Channel Islands and at haul-out sites located between Point Conception and Point Reyes was 153,337. For the same year, the estimated total population in the USA was estimated at 296,750 (Carretta et al. 2014). In Mexico, the species occupies both sides of the Baja California Peninsula. In 2010, the total population size on the Pacific coast was 58,859 individuals (Milanés-Salinas 2012) while the population in the Gulf of California consisted of 32,037 individuals (Aurioles-Gamboa, unpublished data). Thus, the total population of California Sea Lions is approximately 387,646.
The California Sea Lion population is thought to be reaching carrying capacity in the USA (Carretta et al. 2007), however recent censuses suggest the population is still increasing (Carretta et al. 2014). The Gulf of California does not show a similarly marked fluctuation (Szteren et al. 2006, Ward et al. 2010), and animals in the Gulf are genetically isolated from individuals inhabiting the rest of the species’ geographic distribution (Maldonado et al. 1995, Bowen et al. 2005, Schramm et al. 2009).
|Current Population Trend:||Increasing|
|Habitat and Ecology:||The California Sea Lion is a sexually dimorphic species; adult males weigh three to four times more and are up to 1.2 times longer than their female counterparts (King 1964). By two weeks of age, male pups are larger and heavier (75.7 cm, 9.01 kg) than their female counterparts (72.3 cm, 7.6 kg; Le Boeuf et al. 1983). Pups are born with a thick brownish-black lanugo that is generally moulted between the first and second month and is replaced by a darker coat. Nursing may last from one to two years (Newsome et al. 2006). Male California Sea Lions measure up to 255 cm in length and can weigh up to 523 kg (Wright et al. 2010). Females measure up to 200 cm and weigh an average of 110 kg (Peterson and Bartholomew 1967).|
Both sexes usually reach maturity by four to five years of age. Females produce one pup each year, with a gestation period of approximately 11 months. A long-term mark-resighting study (1980-2006) recorded a maximum observed lifespan of 19 years for males and 25 years for females (Hernandez-Camacho et al. 2008a). Mean age-specific birth rates for females vary among age classes: for five-year-olds the rate is 0.59, for six- to 10-year-olds it is 0.79 (Melin 2002, Hernandez-Camacho et al. 2008b), 10- to 12-year-olds exhibit the highest rate (0.80), but the rate gradually decreases for individuals >13 years old to 0.06 in 22 to 25 years olds (Hernandez-Camacho et al. 2008b).
Pupping and breeding take place from May through July. Pupping starts earlier in the Gulf of California (May 8) than off the coast of California (May 20); the duration of the breeding season is also longer in the Gulf (13 weeks) than off the coast of California (9.5 weeks; Garcia-Aguilar and Aurioles-Gamboa 2003a). Males are highly polygynous and defend their territories both on land and in shallow waters near the shore for periods of up to 45 days. A study on the plasticity of male territorial behaviour in response to varying environmental conditions showed that males inhabiting high-temperature environments (air temperatures >30°C, e.g., the Gulf of California) defend territories adjacent to the coast while immersed in the water (Bohorquez-Herrera et al. 2014). Females remain on shore with their newborn pups for approximately seven days before they depart for the first of many foraging trips that usually last two to three days, followed by another one to two days of caring for their pups at the rookery (Melin et al. 2000, García-Aguilar and Aurioles-Gamboa 2003b).
Following the breeding season, large numbers of adult and subadult males and juveniles migrate north from the major rookeries in southern California and Baja California and winter from central California to Washington (Fry 1939, Odell 1975, Mate 1975). Smaller numbers of animals migrate to British Columbia (Wright et al. 2010) and southeast Alaska, reaching the northern Gulf of Alaska, the Alaska Peninsula, and the eastern Aleutian Islands (Maniscalco et al. 2004). Other animals remain in the Gulf of California year round and do not undertake long migrations; however, the arrival of numerous adult and subadult males is observed every year at several rookeries and haul-out areas around the southern tip of the Baja California Peninsula (Aurioles-Gamboa et al. 1983).
During the breeding (warm) season, 96% of the dives by lactating adult females from San Miguel Island, California were to depths of eight to 75 m with 92% of dives lasting less than four minutes. During the non-breeding (cold) season, 77% of the dives were between eight and 75 m and 81% lasted four minutes or less. Most dives during both the breeding (84.5%) and non-breeding (81.2%) seasons occurred less than 150 km from San Miguel Island (Melin and DeLong 2000).
During the breeding season, the average dive depth for lactating adult females in the Gulf of California is 81.7±32 m with average dive duration of 3.5±0.9 min. During the cold season, dive depth and duration average 48.9±18.5 m and 1.7±0.6 min, respectively. The distance travelled during the breeding and cold season varies from 72.7±21.8 km to 101.2±18.5 km, respectively (Villegas-Amtmann et al. 2011). Adult females and males exhibit three distinct foraging behaviors to exploit the benthic, epi-pelagic and meso-pelagic environments (Weise et al. 2010, Villegas-Amtmann et al. 2011).
California Sea Lions are generally found in waters over the continental shelf and slope zones; they also frequent coastal areas, including bays, harbours and river mouths. Their feeding habits are influenced by coastal ecosystems and they consume a wide variety of prey. However, they usually prefer four to five species at each site, often consuming what is abundant locally or seasonally in the areas they occupy (Lowry et al. 1990, Garcia-Rodriguez and Aurioles-Gamboa 2004). Their main prey in California are Pacific Sardines (Sardinops sagax), Northern Anchovies (Engraulis mordax), Pacific Hake (Merlucius productus), Jack Mackerel (Trachurus symmetricus), Pacific Mackerel (Scomber japonicus), various species of the genus Sebastes, Red Octopus (Octopus rubescens) and Market Squid (Loligo opalescens; Antonelis et al. 1984, Lowry et al. 1990, Lowry 1991, Lowry and Carretta 1999). On the Pacific coast of Baja California, Sea Lions consume many of the same prey species as well as north Pacific Argentine (Argentina sialis) and Jumbo Squid (Dosidicus gigas; Aurioles-Gamboa and Camacho-Rios 2007). In the Gulf of California, the main prey species include those listed above and many other fish and squid species, including Pacific Cutlassfish (Trichiurus lepturus), Plainfin Midshipman (Porichthys notatus), Anchoveta (Cetengraulis mysticetus), Eastern Pacific Flagfin (Aulopus bajacali), Bigeye Bass (Pronotogrammus eos) and Deepwater Serrano (Serranus aequidens; Aurioles-Gamboa et al. 1984, Garcia-Rodriguez and Aurioles-Gamboa 2004).
Ontogenetic differences in diving capacities and feeding habits have been documented for California Sea Lions (Weise and Costa 2007, Orr et al. 2011), which can be affected by El Niño and La Niña events (Lowry and Carretta 1999, Weise and Harvey 2008). During the 1993 El Niño, adult females travelled farther from the colony, spent more time travelling, made deeper and longer dives, and terminated lactation earlier compared to 1996. Their mean dive depths varied from 19.5 to 279.3 m, but most females made some dives deeper than 400 m (Melin et al. 2008). During one unusually warm year, adult males that forage almost exclusively over the continental shelf altered their foraging effort by spending more time at sea and venturing up to 450 km offshore (Weise et al. 2006).
Due to their coastal distribution, abundance and feeding habits, California Sea Lions interact with several fisheries, including those for Pacific Salmon (DeMaster et al. 1982, DeMaster et al. 1985, Aurioles-Gamboa et al. 2003, Weise and Harvey 2005, Weise and Harvey 2008), causing economic losses for sport and commercial fishermen and a high incidence of Sea Lion entanglement (Stewart and Yochem 1987, Harcourt et al. 1994, Zavala and Mellink 1996, Aurioles-Gamboa et al. 2003).
Predators of California Sea Lions include Killer Whales, Sharks, Coyotes and feral Dogs. Before their recent eradication from California’s Channel Islands, Bald Eagles were known to take young pups.
|Continuing decline in area, extent and/or quality of habitat:||No|
|Generation Length (years):||14.5|
|Movement patterns:||Not a Migrant|
|Congregatory:||Congregatory (and dispersive)|
|Use and Trade:||
California Sea Lions were historically important to indigenous people living in coastal areas and on islands used by Sea Lions for rookeries (Arellano-Peralta and Medrano-Gonzalez 2015). Huge middens in southern California and on the Channel Islands with large numbers of California Sea Lion and other pinniped bones attest to the past importance of marine mammals for subsistence prior to the changes that followed the arrival of Europeans on the west coast of North America (Porcasi et al. 2000, Braje and DeLong 2009). In the 19th and early 20th centuries, California Sea Lions were harvested intensively for a variety of products and hunted for bounties to reduce their impact on fisheries (Cass 1985, Gerber and Hillborn 2001, Arellano-Peralta and Medrano-Gonzalez 2015).
Conflicts with fisheries, poaching and entanglement in marine debris contribute to California Sea Lion mortality (Stewart and Yochem 1987, Howorth 1994, Harcourt et al. 1994, Zavala and Mellink 1996, Aurioles-Gamboa et al. 2003). Prey availability is greatly reduced during El Niño events and large numbers of pups born during these periods die of starvation, as do weaker animals of all age classes (Francis and Heath 1991, Shirasago-German et al. 2015). Sea lion rookeries in the Gulf of California do not appear to be greatly influenced by El Niño events (Aurioles and Le Boeuf 1991, Szteren et al. 2006).
California Sea Lions accumulate pollutants through the food chain, and large amounts of DDT and PCBs discharged in the past continue to accumulate in coastal marine food chains that include this species (DeLong et al. 1973, Le Boeuf et al. 2002). California Sea Lions occasionally die of paralytic shellfish poisoning caused by domoic acid, a biotoxin produced by diatom blooms that enters the food web through planktivorous fish, such as Herring and Sardines (Scholin et al. 2000, Silvagni et al. 2005). Diseases also contribute to California Sea Lion mortality, including some contracted from terrestrial animals, like leptospirosis (Vedros et al. 1971), an endemic disease with periodic epidemics of acute disease (Lloyd-Smith et al. 2007). Contact with feral and domestic dogs and other terrestrial animals may expose the species to additional diseases like brucellosis, which may cause miscarriages (Goldstein et al. 2009, Avalos-Tellez et al. 2014).
Protection, which began in the mid-20th century in the United States, was solidified with the passage of the U.S. Marine Mammal Protection Act of 1972 and similar laws in Mexico. These protective measures provided the impetus for recovery of the population. At coastal sites and on most offshore islands, tourism is highly regulated and controlled. The National Marine Fisheries Service regularly monitors the California Sea Lion population in US waters. The Mexican federal government’s Comisión Nacional de Areas Naturales Protegidas (National Commission of Natural Protected Areas) has conducted annual censuses and monitored the health of the California Sea Lion populations in the Gulf of California since 2011.
|Citation:||Aurioles-Gamboa, D. & Hernández-Camacho, J. 2015. Zalophus californianus. The IUCN Red List of Threatened Species 2015: e.T41666A45230310.Downloaded on 22 October 2017.|
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