Zalophus californianus (Lesson, 1828)
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publication ID |
https://doi.org/ 10.5281/zenodo.6604474 |
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DOI |
https://doi.org/10.5281/zenodo.6604533 |
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persistent identifier |
https://treatment.plazi.org/id/965C87FE-1E51-5641-9CBC-9B348AF4F93C |
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treatment provided by |
Diego |
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scientific name |
Zalophus californianus |
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California Sea Lion
Zalophus californianus View in CoL
French: Otarie de Californie / German: Kalifornischer Seelowe / Spanish: Le 6n marino de California
Other common names: California Sealion, Californian Sea Lion
Taxonomy. Otaria californiana Lesson, 1828 View in CoL ,
“les rochers dans le voisinage de la baie San-Francisco” (= San Francisco Bay), California, United States .
Formerly referred to as Z. c. californianus , one of three subspecies of Z. californianus .
Three closely related taxa, Z. californianus , Z. wollebaeki , and the extinct Z. japonicus are now full species. Monotypic.
Distribution. E North Pacific Ocean from SC Alaska to Islas Marias off Nayarit, Mexico, including the Gulf of California. View Figure
Descriptive notes. Total length 240 cm (males) and 200 cm (females); weight 390 kg or more (males) and 110 kg (females). Newborns are 80 cm and 6-9 kg. Dental formula varies, 79% =13/2,C1/1,PC5/85 (x2) =534,21%=15%/2,C 1/1, PC 6/5 (x 2) = 36. The California Sea Lion is arguably the most familiar of pinnipeds, being the “circus seal” trained to perform at marine aquaria and zoos. It is sexual dimorphic, with adult males 3—4 times heavier and 1-2 times longer than females. Males have enlarged neck, chest, and shoulders, and they develop sagittal crest on skull that creates very pronounced forehead. Because females and juveniles lack sagittal crests, they have flatter heads. Adult females also have more gracile necks. Muzzles of both sexes are long, tapering to blunt rhinaria (nose) that make profiles reminiscent of a dog, particularly in younger individuals. Foreflippers have some hair on dorsal surfaces, but the hair does not extend to rounded tips. Otherwise, flippers, including undersides, are covered with dark leathery skin. First digit is the longest and curves back. Cartilaginous rods in hindflippers lengthen toes, and first and fifth digits are longer than three middle digits. Similar to foreflippers, hindflippers have hair on upper parts closest to body but otherwise are covered in dark leathery skin. Coat color of males begins to darken as they reach sub-adulthood, ultimately turning dark brown in most animals, but wet individuals look black. Some male California Sea Lions are pale-brown. Adult females and juveniles are a warm buff color above, with darker browns on bellies and nearflippers. Face of adult males can have pale areas on muzzle and ear pinnae and around eyes. Prominent sagittal crest in males is accentuated by paler hair on steep forehead. Newborns have blackish-brown natal coat that is soon shed for a pale-brown coat that is molted at 5-6 months of age. As they approach their annual molt, coloration of California Sea Lions, at any age, can look dull and grayish.
Habitat. Over continental shelf and slope and cross deep pelagic waters to reach islands such as Alijos Rocks and Guadalupe Island, west of Baja California. California Sea Lions are commonly seen in bays, harbors, estuaries, and, to a lesser extent, rivers. Rookeries and haul-outs are typically located on rocks or sandy or rocky beaches. Favored haul-outsites are coastal headlands and cliffs that prevent terrestrial predators from approaching. They will also haul out on manmade structures such as jetties, buoys, docks, and boats at anchor. Marine predators include Killer Whales (Orcinus orca) and sharks, and terrestrial predators include Coyotes ( Canis latrans) and feral dogs. Bald eagles (Haliaetus leucocephalus) were once known to prey on neonates on the Channel Islands of California.
Food and Feeding. The diet of the California Sea Lion is extremely varied. On the outer Pacific coast prey includes whiting, jack, mackerel, blacksmith (Chromis punctipinnis), rockfish ( Sebastidae ), herring, northern anchovy ( Engraulidae ), salmon ( Salmonidae ), squid, and octopus. In the Gulf of California, in addition to northern anchovy, whiting, and rockfish, they eat midshipman fish (Porichthys spp.), lanternfish ( Myctophidae ), bass, sardines ( Clupeidae ), cutlassfish and hairtails ( Trichiuridae ), aulopus ( Aulopidae ), and cusk-eels ( Ophidiidae ). California Sea Lions will travel far upriver in pursuit of food and are notorious for aggregating at the base of the Bonneville Dam on the Columbia River between Washington and Oregon, USA—some 233 km inland—to prey on runs of migrating salmon.
Breeding. The California Sea Lion has the same general polygynous breeding system as described for the New Zealand Sea Lion ( Phocarctos hookeri ). For the California Sea Lion, breeding season is in May—July and lasts 3-5 weeks longer in the Gulf of California than along the southern California coast. Births in May occur c.12 days earlier in the Gulf of California than on the west coast of California. Males maintain territories on beaches and in nearshore water for up to 45 days. Females give birth to a single neonate after an 11month gestation and then remain with the neonate for c.7 days before leaving to feed at sea for 2-3 days. They return for nursing bouts that last 1-2 days. Weaning takes place when young are a year old, but prior to weaning, they accompany their mothers on trips to sea. Females may extend care for a year, or even as much as 2-3 years. Females enter estrus c.27 days after giving birth. An unusual otariid breeding behavior occurs in California Sea Lions, where females form “milling groups” on the beach. They roll in the splash zone and on the sand, mounting each other and even nearby males in an apparent bid for male attention. The milling group breaks up after a male copulates with one of the females. Males and females attain sexual maturity at 4-5 years of age. The California Sea Lion has been known to hybridize with Northern Fur Seals ( Callorhinus ursinus ) and Guadalupe Fur Seals ( Arctocephalus townsend). Life span of the California Sea Lion is c.15-24 years.
Activity patterns. At sea, California Sea Lions are frequently observed rafting at the water’s surface, singly or in groups. They often maintain a resting pose by holding a flipper high out of the water. They will also doze offshore, sometimes in the fronds of kelp. They may associate with cetaceans (e.g. following ocean dolphins), possibly as a means of locating suitable prey. They are known to travel alongside large baleen whales, including Humpback Whales (Megaptera novaeangliae) and Blue Whales (Balaenoptera musculus), and even ride whales’ bow waves. California Sea Lions are acrobatic and can be seen making high jumps, surfing waves near the beach, and riding stern wakes of ships. They “porpoise,” or leap from the water, when swimming at high speed. From a distance, groups of porpoising sea lions can appear to be a group of ocean dolphins. Generally, California Sea Lions are not deep divers. Average foraging dive of lactating females is less than 80 m and lasts less than three minutes. Maximum depth of a dive in one study was 274 m, with the longest duration of almost ten minutes. Lactating females are active nearly the entire time they spend at sea, foraging day and night, with an increase in diving during twilight hours. Ashore, adult males are among the most vocal pinniped. Territorial males can bark incessantly. Their bark is loud and monotonous, often made with a side-to-side wave of the head. Females and young individuals do not repetitively bark. California Sea Lions are tolerant of other species of pinnipeds and are known to haul out with Steller Sea Lions ( Eumetopias jubatus), Guadalupe Fur Seals, Northern Fur Seals, Northern Elephant Seals (Mirounga angustirostris), and occasionally Harbor Seals (Phoca vitulina).
Movements, Home range and Social organization. Male California Sea Lions tend to be migratory, traveling north from major rookeries after the breeding season. Large numbers of them will travel up the coast from 13 major colonies in Baja California and southern California, with some making it to British Columbia, south-eastern Alaska, and as far as the Gulf of Alaska. Most rookeries are south of Point Conception, California. The California Sea Lion is spreading north, and females are now regularly seen in northern California where historic breeding locations have been reoccupied. It is resident in the Gulf of California throughout the year, and that population is apparently more sedentary, refraining from long distance travel away from the 13 rookeries located there. Vagrant California Sea Lions have reached the Bering Sea in the north and the Mexican state of Chiapas in the south.
Status and Conservation. Classified as Least Concern on The IUCN Red List. The population of California Sea Lions is thriving and numbers ¢.355,000 individuals. Numbers are increasing in California, where the population is ¢.238,000 individuals, perhaps approaching maximum carrying capacity. In Mexico, the west coast of the Baja California Peninsula has a population of ¢.75,000-87,000 individuals. The Gulf of California population is ¢.30,000 individuals, a decrease of ¢.20% in the last 15 years, and some rookeries have experienced reductions of 35% in this same time period. California Sea Lions were hunted by indigenous peoples, as evidenced by their skeletal material in middens (collections of domestic waste) in southern California. They were harvested commercially in the 19" and 20" centuries, and because they were viewed as pests, government bounties led to dramatic population reductions. Hunting bans in the mid-20" century culminated with the US Marine Mammal Protection Act. This and similar legal action in Mexico have allowed populations to recover. Mortality persists due to fisheries conflicts and entanglement in marine debris. California Sea Lions are bold predators, willing to steal salmon and rockfish off fishing hooks, making them a nuisance to commercial fisheries. They are also at risk from pollutants in the food chain, especially persistent organochlorines (e.g. DDT and PCBs) and pesticides from urban discharges and agricultural runoff into coastal waters. California Sea Lions are susceptible to lethal poisoning caused by domoic acid, a biotoxin produced by marine diatom blooms. They can also contract diseases from terrestrial animals, including leptospirosis. Natural cycles in the marine environment can have a major impact on the California/Baja California population. During EI Nino events, food resources are scarce and young and weaker individuals often starve to death. It may take 4-5 years before a population recovers after a severe El Nino event. The Gulf of California population is not subject to such extreme fluctuations, although it has been in a moderate decline.
Bibliography. Antonelis, Fiscus & Delong (1984), Antonelis, Stewart & Perryman (1990), Aurioles-Gamboa & Zavala-Gonzalez (1994), Aurioles-Gamboa, Fox et al. (1984), Aurioles-Gamboa, Garcia-Rodriguez et al. (2003), Aurioles & Trillmich (2008e), Bearzi (2006), Feldkamp et al. (1989), Francis & Heath (1991), Garcia-Aguilar & Aurioles-Gamboa (2003), Gerber et al. (2010), Heath & Perrin (2009), Hernandez-Camacho et al. (2008), Jefferson et al. (2008), Lowry & Maravilla-Chavez (2005), Lowry et al. (1991), Maldonado et al. (1995), Maniscalco et al. (2004), Odell (1981), Peterson & Bartholomew (1967), Porras-Peters et al. (2008), Reijnders et al. (1993), Rice (1998), Robertson et al. (2008), Schramm et al. (2009), Stewart & Yochem (1987), Szteren et al. (2006), Wielgus et al. (2008), Wright et al. (2010), Young & Gerber (2008), Zavala-Gonzalez & Mellink (1997).
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