California Sea Lions
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The California sea lion (''Zalophus californianus'') is a coastal
eared seal An eared seal or otariid or otary is any member of the marine mammal family Otariidae, one of three groupings of pinnipeds. They comprise 15 extant species in seven genera (another species became extinct in the 1950s) and are commonly known eith ...
native to western
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. It is one of six species of
sea lions Sea lions are pinnipeds characterized by external ear flaps, long foreflippers, the ability to walk on all fours, short and thick hair, and a big chest and belly. Together with the fur seals, they make up the family Otariidae, eared seals. ...
. Its natural habitat ranges from
southeast Alaska Southeast Alaska, colloquially referred to as the Alaska(n) Panhandle, is the southeastern portion of the U.S. state of Alaska, bordered to the east and north by the northern half of the Canadian province of British Columbia (and a small part ...
to central
Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
, including the
Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...
. California sea lions are
sexually dimorphic Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
; males are larger than females, and have a thicker neck, and a protruding
sagittal crest A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are exceptiona ...
. They mainly haul-out on sandy or rocky beaches, but they also frequent manmade environments such as
marina A marina (from Spanish , Portuguese and Italian : ''marina'', "coast" or "shore") is a dock or basin with moorings and supplies for yachts and small boats. A marina differs from a port in that a marina does not handle large passenger ships o ...
s and
wharves A wharf, quay (, also ), staith, or staithe is a structure on the shore of a harbour or on the bank of a river or canal where ships may dock to load and unload cargo or passengers. Such a structure includes one or more berths (mooring location ...
. California sea lions feed on a number of species of fish and squid, and are preyed on by
orca The orca or killer whale (''Orcinus orca'') is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. It is the only Extant taxon, extant species in the genus ''Orcinus'' and is recognizable by its black ...
s and
great white shark The great white shark (''Carcharodon carcharias''), also known as the white shark, white pointer, or simply great white, is a species of large mackerel shark which can be found in the coastal surface waters of all the major oceans. It is nota ...
s. California sea lions have a
polygynous Polygyny (; from Neoclassical Greek πολυγυνία (); ) is the most common and accepted form of polygamy around the world, entailing the marriage of a man with several women. Incidence Polygyny is more widespread in Africa than in any ...
breeding pattern. From May to August, males establish
territories A territory is an area of land, sea, or space, particularly belonging or connected to a country, person, or animal. In international politics, a territory is usually either the total area from which a state may extract power resources or a ...
and try to attract females with which to mate. Females are free to move in between territories, and are not coerced by males. Mothers nurse their pups in between foraging trips. California sea lions communicate with numerous vocalizations, notably with barks and mother-pup
contact call Contact calls are seemingly haphazard sounds made by many social animals (such as a chicken's cluck). Contact calls are unlike other calls (such as alarm calls) in that they are not usually widely used, conspicuous calls, but rather short exclamatio ...
s. Outside their breeding season, California sea lions spend much of their time at sea, but they come to shore to
molt In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
. California sea lions are particularly intelligent, can be trained to perform various tasks and display limited fear of humans if accustomed to them. Because of this, California sea lions are a popular choice for public display in
zoo A zoo (short for zoological garden; also called an animal park or menagerie) is a facility in which animals are kept within enclosures for public exhibition and often bred for conservation purposes. The term ''zoological garden'' refers to zoo ...
s,
circus A circus is a company of performers who put on diverse entertainment shows that may include clowns, acrobats, trained animals, trapeze acts, musicians, dancers, hoopers, tightrope walkers, jugglers, magicians, ventriloquists, and unicyclist ...
es and
oceanarium An oceanarium can be either a marine mammal park, such as Marineland of Canada, or a large-scale aquarium, such as the Lisbon Oceanarium, presenting an ocean habitat with marine animals, especially large ocean dwellers such as sharks. First ma ...
s, and are trained by the United States Navy for certain military operations. The
International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
(IUCN) lists the species as
Least Concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...
due to its abundance. To protect fish, the US states of
Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...
and
Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...
engage in annual kill quotas of California sea lions.


Taxonomy

The California sea lion was described by
René Primevère Lesson René (''born again'' or ''reborn'' in French) is a common first name in French-speaking, Spanish-speaking, and German-speaking countries. It derives from the Latin name Renatus. René is the masculine form of the name (Renée being the feminine ...
, a French naturalist, in 1828. It is grouped with other sea lions and
fur seal Fur seals are any of nine species of pinnipeds belonging to the subfamily Arctocephalinae in the family '' Otariidae''. They are much more closely related to sea lions than true seals, and share with them external ears (pinnae), relatively lon ...
s in the family Otariidae. Otariids, also known as eared seals, differ from
true seals The earless seals, phocids or true seals are one of the three main groups of mammals within the seal lineage, Pinnipedia. All true seals are members of the family Phocidae (). They are sometimes called crawling seals to distinguish them from th ...
in having external ear flaps, and proportionately larger foreflippers and pectoral muscles. Along with the Galapagos sea lion and the extinct
Japanese sea lion The Japanese sea lion (''Zalophus japonicus'') ( ja, ニホンアシカ, translit=Nihon ashika, Korean:강치, 바다사자) was an aquatic mammal that became extinct in the 1970s. It was considered to be a subspecies of the related California se ...
, the California sea lion belongs to the genus '' Zalophus'', which derives from the Greek words ''za'', meaning "intensive," and ''lophus,'' meaning "crest." This refers to the protruding
sagittal crest A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are exceptiona ...
of the males, which distinguishes members of the genus. Traditionally, the Galapagos sea lion and Japanese sea lion were classified as
subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
of the California sea lion. However, a genetic study in 2007 found that all three are in fact separate species. The lineages of the California and Japanese sea lion appear to have split off 2.2 million years ago during the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
. The
Steller sea lion The Steller sea lion (''Eumetopias jubatus''), also known as the Steller's sea lion and northern sea lion, is a near-threatened species of sea lion in the northern Pacific. It is the sole member of the genus ''Eumetopias'' and the largest of t ...
is the closest extant relative of the ''Zalophus'' sea lions, being a
sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...
.


Appearance, physiology, and movement

Being sexually dimorphic, California sea lions differ in size, shape, and coloration between the sexes. Males can grow up to long and weigh up to , while females are typically around and weigh up to . Females and juveniles have a tawny brown
pelage Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily #Guard hair, guard hair on top and thick #Down hair, underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as ...
, although they may be temporarily light gray or silver after
molting In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
. The pelage of adult males can be anywhere from light brown to black, but is typically dark brown. The face of adult males may also be light tan in some areas. Pups have a black or dark brown pelage at birth. Although the species has a slender build, adult males have robust necks, chests, and shoulders. Adult males also have a protruding crest which gives them a "high, domed forehead"; it is tufted with white hairs. They also have manes, which are less developed than those of adult male
South American South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
and Steller sea lions. Both sexes have long, narrow muzzles. As an otariid, the California sea lion relies on its foreflippers to propel itself when swimming. This form of
aquatic locomotion Aquatic locomotion or swimming is biologically propelled motion through a liquid medium. The simplest propulsive systems are composed of cilia and flagella. Swimming has evolved a number of times in a range of organisms including arthropods, fi ...
, along with its streamlined body, effectively reduces drag underwater. Its foreflipper movement is not continuous; the animal glides in between each stroke. The flexibility of its spine allows the California sea lion to bend its neck backwards far enough to reach its hindflippers. This allows the animal to make dorsal turns and maintain a streamlined posture. When moving on land, the California sea lion is able to turn its hindflippers forward and walk on all fours. It moves the foreflippers in a
transverse Transverse may refer to: *Transverse engine, an engine in which the crankshaft is oriented side-to-side relative to the wheels of the vehicle *Transverse flute, a flute that is held horizontally * Transverse force (or ''Euler force''), the tangen ...
, rather than a
sagittal The sagittal plane (; also known as the longitudinal plane) is an anatomical plane that divides the body into right and left sections. It is perpendicular to the transverse and coronal planes. The plane may be in the center of the body and divi ...
, fashion. In addition, it relies on movements of its head and neck more than its hindflippers for terrestrial locomotion. California sea lions may travel at speeds of around , and can dive at depths of and for up to 9.9 minutes, though most dives are typically and last less than 3 minutes. California sea lions have
color vision Color vision, a feature of visual perception, is an ability to perceive differences between light composed of different wavelengths (i.e., different spectral power distributions) independently of light intensity. Color perception is a part of ...
, though it is limited to the blue-green area of the
color spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' or simply light. A typical human eye wil ...
. This is likely an adaptation for living in marine coastal habitats. Sea lions have fairly acute underwater hearing, with a hearing range of 0.4–32
kHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
. California sea lions rely on their
whiskers Vibrissae (; singular: vibrissa; ), more generally called Whiskers, are a type of stiff, functional hair used by mammals to touch, sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are c ...
or vibrissae for touch and detection of vibrations underwater. Compared to the
harbor seal The harbor (or harbour) seal (''Phoca vitulina''), also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere. The most widely distributed species of pinniped (walruses, eared sea ...
, the California sea lion's vibrissae are smoother and less specialized and thus perform less when following hydrodynamic trails, although they still perform well.


Ecology


Range and habitat

The California sea lion ranges along the western coast and islands of
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
, from
southeast Alaska Southeast Alaska, colloquially referred to as the Alaska(n) Panhandle, is the southeastern portion of the U.S. state of Alaska, bordered to the east and north by the northern half of the Canadian province of British Columbia (and a small part ...
to central
Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
.
Mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...
sequences in 2009 have identified five distinct California sea lion populations: the U.S. or Pacific Temperate stock, the Western
Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
or Pacific Tropical stock, and the Southern, Central, and Northern
Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...
stocks. The U.S. stock breeds mainly in the
Channel Islands The Channel Islands ( nrf, Îles d'la Manche; french: îles Anglo-Normandes or ''îles de la Manche'') are an archipelago in the English Channel, off the French coast of Normandy. They include two Crown Dependencies: the Bailiwick of Jersey, ...
, although some breeding sites may be established in
northern California Northern California (colloquially known as NorCal) is a geographic and cultural region that generally comprises the northern portion of the U.S. state of California. Spanning the state's northernmost 48 counties, its main population centers incl ...
, and females are now commonly found there. The Western Baja California stock mainly breeds near
Punta Eugenia Punta Eugenia is a headland in the Mulegé Municipality. It marks the Western tip of the Vizcaíno Peninsula, thus being the westernmost point on the mainland of the state of Baja California Sur. It belongs to the larger area of El Vizcaíno Bio ...
and at
Isla Santa Margarita Isla or ISLA may refer to: Organizations * International Securities Lending Association, a trade association * International School of Los Angeles * International Bilingual School, later named International School of Los Angeles People * Isla (g ...
. The above-mentioned stocks are separated by the Ensenada Front. The stocks of the Gulf of California live in the shallow waters of the north (Northern stock), the
tidal island A tidal island is a piece of land that is connected to the mainland by a natural or man-made causeway that is exposed at low tide and submerged at high tide. Because of the mystique surrounding tidal islands, many of them have been sites of ...
s near the center (Central stock), and the mouth of the bay (Southern stock). The stock status of the California sea lions at the deep waters of the central bay has not been analyzed. Vagrants can reach western north pacific such as on
Commander Islands The Commander Islands, Komandorski Islands, or Komandorskie Islands (russian: Командо́рские острова́, ''Komandorskiye ostrova'') are a series of treeless, sparsely populated Russian islands in the Bering Sea located about ea ...
. Although several otariinae have been recorded around the Japanese archipelago in recent years, their exact origins are unclear. During the breeding season, California sea lions gather on both sandy and rocky shores. On warm days, they lie closer to the water. At night or in cool weather, they travel farther inland or to higher elevations. Non-breeding individuals may gather at
marina A marina (from Spanish , Portuguese and Italian : ''marina'', "coast" or "shore") is a dock or basin with moorings and supplies for yachts and small boats. A marina differs from a port in that a marina does not handle large passenger ships o ...
s,
wharves A wharf, quay (, also ), staith, or staithe is a structure on the shore of a harbour or on the bank of a river or canal where ships may dock to load and unload cargo or passengers. Such a structure includes one or more berths (mooring location ...
, or even navigational
buoy A buoy () is a floating device that can have many purposes. It can be anchored (stationary) or allowed to drift with ocean currents. Types Navigational buoys * Race course marker buoys are used for buoy racing, the most prevalent form of yac ...
s. California sea lions can also live in
fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
for periods of time, such as near
Bonneville Dam Bonneville Lock and Dam consists of several run-of-the-river dam structures that together complete a span of the Columbia River between the U.S. states of Oregon and Washington at River Mile 146.1. The dam is located east of Portland, Oregon, ...
, nearly up the
Columbia River The Columbia River (Upper Chinook: ' or '; Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, C ...
. In 2004, a healthy California sea lion was found sitting on a road in
Merced County Merced County ( ), is a county located in the northern San Joaquin Valley section of the Central Valley, in the U.S. state of California. As of the 2020 census, the population was 281,202. The county seat is Merced. The county is named after ...
, California, almost a hundred miles upstream from the
San Francisco Bay San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, and Oakland. San Francisco Bay drains water from a ...
and half a mile from the
San Joaquin River The San Joaquin River (; es, Río San Joaquín) is the longest river of Central California. The long river starts in the high Sierra Nevada, and flows through the rich agricultural region of the northern San Joaquin Valley before reaching Suis ...
.


Diet and predation

California sea lions feed on a wide variety of
seafood Seafood is any form of sea life regarded as food by humans, prominently including fish and shellfish. Shellfish include various species of molluscs (e.g. bivalve molluscs such as clams, oysters and mussels, and cephalopods such as octopus an ...
, mainly
squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...
and
fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
, and sometimes
clam Clam is a common name for several kinds of bivalve molluscs. The word is often applied only to those that are edible and live as infauna, spending most of their lives halfway buried in the sand of the seafloor or riverbeds. Clams have two she ...
s. Commonly eaten fish and squid species include
salmon Salmon () is the common name for several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the family (biology), family Salmonidae, which are native to tributary, tributaries of the ...
,
hake The term hake refers to fish in the: * Family Merlucciidae of northern and southern oceans * Family Phycidae (sometimes considered the subfamily Phycinae in the family Gadidae) of the northern oceans Hake Hake is in the same taxonomic order (Gad ...
,
Pacific whiting The North Pacific hake, Pacific hake, Pacific whiting, or jack salmon (''Merluccius productus'') is a ray-finned fish in the genus '' Merluccius'', found in the northeast Pacific Ocean from northern Vancouver Island to the northern part of the Gu ...
,
anchovy An anchovy is a small, common forage fish of the family Engraulidae. Most species are found in marine waters, but several will enter brackish water, and some in South America are restricted to fresh water. More than 140 species are placed in 1 ...
,
herring Herring are forage fish, mostly belonging to the family of Clupeidae. Herring often move in large schools around fishing banks and near the coast, found particularly in shallow, temperate waters of the North Pacific and North Atlantic Oceans, i ...
,
rockfish Rockfish is a common term for several species of fish, referring to their tendency to hide among rocks. The name rockfish is used for many kinds of fish used for food. This common name belongs to several groups that are not closely related, and ca ...
,
lamprey Lampreys (sometimes inaccurately called lamprey eels) are an ancient extant lineage of jawless fish of the order Petromyzontiformes , placed in the superclass Cyclostomata. The adult lamprey may be characterized by a toothed, funnel-like s ...
, dogfish, and market squid. They mostly forage near mainland coastlines, the
continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...
, and
seamount A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abru ...
s. They may also search along the ocean bottom. California sea lions may eat alone or in small to large groups, depending on the amount of food available. They sometimes cooperate with other predators, such as
dolphin A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the ...
s,
porpoise Porpoises are a group of fully aquatic marine mammals, all of which are classified under the family Phocoenidae, parvorder Odontoceti (toothed whales). Although similar in appearance to dolphins, they are more closely related to narwhals an ...
s, and
seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same enviro ...
s, when hunting large schools of fish. California sea lions sometimes follow dolphins and exploit their hunting efforts. Adult females feed between from shore. Adult males may forage as far as from shore when water temperatures rise. They also have learned to feed on
steelhead Steelhead, or occasionally steelhead trout, is the common name of the anadromous form of the coastal rainbow trout or redband trout (O. m. gairdneri). Steelhead are native to cold-water tributaries of the Pacific basin in Northeast Asia and N ...
and salmon below
fish ladder A fish ladder, also known as a fishway, fish pass, fish steps, or fish cannon is a structure on or around artificial and natural barriers (such as dams, locks and waterfalls) to facilitate diadromous fishes' natural migration as well as movemen ...
s at Bonneville Dam and at other locations where fish must queue in order to pass through dams and locks that block their passage. California sea lions are preyed on by
orca The orca or killer whale (''Orcinus orca'') is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. It is the only Extant taxon, extant species in the genus ''Orcinus'' and is recognizable by its black ...
s and large
shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...
s. At
Monterey Bay Monterey Bay is a bay of the Pacific Ocean located on the coast of the U.S. state of California, south of the San Francisco Bay Area and its major city at the south of the bay, San Jose. San Francisco itself is further north along the coast, by a ...
, California sea lions appear to be the more common food items for transient mammal-eating orcas pods. The California sea lions may respond to the dorsal fin of a killer whale and remain vigilant, even when encountering resident fish-eating pods. California sea lions are also common prey for
great white shark The great white shark (''Carcharodon carcharias''), also known as the white shark, white pointer, or simply great white, is a species of large mackerel shark which can be found in the coastal surface waters of all the major oceans. It is nota ...
s. They have been found with scars made by attacks from both great white sharks and
shortfin mako shark The shortfin mako shark (; ; ''Isurus oxyrinchus''), also known as the blue pointer or bonito shark, is a large mackerel shark. It is commonly referred to as the mako shark, as is the longfin mako shark (''Isurus paucus''). The shortfin mako can ...
s. Sharks attack California sea lions by ambushing them while they are resting at the surface. California sea lions that are attacked in the hindquarters are more likely to survive and make it to the shore.


Life history


Reproductive behavior and parenting

California sea lions breed gregariously between May and August, when they arrive at their breeding
rookeries A rookery is a colony of breeding animals, generally gregarious birds. Coming from the nesting habits of rooks, the term is used for corvids and the breeding grounds of colony-forming seabirds, marine mammals ( true seals and sea lions), and ...
. When establishing a
territory A territory is an area of land, sea, or space, particularly belonging or connected to a country, person, or animal. In international politics, a territory is usually either the total area from which a state may extract power resources or a ...
, the males will try to increase their chances of reproducing by staying on the rookery for as long as possible. During this time, they will fast, relying on a thick layer of fat called
blubber Blubber is a thick layer of vascularized adipose tissue under the skin of all cetaceans, pinnipeds, penguins, and sirenians. Description Lipid-rich, collagen fiber-laced blubber comprises the hypodermis and covers the whole body, except for pa ...
for energy. Size and patience allow a male to defend his territory more effectively; the bigger the male, the more blubber he can store and the longer he can wait. A male California sea lion usually keeps his territory for around 27 days. Females have long
parturition Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the f ...
intervals, and thus the males do not establish their territories until after the females give birth. Most fights occur during this time. After this, the males rely on ritualized displays (vocalizations, head-shaking, stares, bluff lunges, and so on) to maintain their territorial boundaries. Since temperatures can reach over during this time, males must include water within their territories. Some territories are underwater, particularly those near steep cliffs. California sea lions that fail to establish a territory are driven out to sea or gather at a nearby beach. Before mating begins, females gather into "milling" groups of 2–20 individuals. The females in these groups will mount each other as well as the males. These groups begin to disintegrate as the females begin to mate. The territorial and mating system of the California sea lion has been described as similar to a
lek Lek or LEK may refer to: * Lek mating, mating in a lek, a type of animal territory in which males of a species gather * Albanian lek, the currency of Albania * Lek (magazine), a Norwegian softcore pornographic magazine * Lek (pharmaceutical comp ...
system, as females appear to choose their mates while moving through different territories. They avoid males that are too aggressive or energetic. Males are usually unable to prevent females from leaving their territories, particularly in water. Mating may occur outside the rookeries, between non-territorial males and females, as the latter move to and from the mating site. In some rookeries, copulation may be monopolized by a few males, while at others, a single male may sire no more than four pups. Female California sea lions have a 12-month reproductive cycle, consisting of a 9-month actual
gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...
and a 3-month delayed implantation of the fertilized egg before giving birth in June or July. Interbirth intervals are particularly long for this species, being 21 days for sea lions off California and more than 30 days for sea lions in the Gulf of California. Females remain with their pups onshore for 10 days and nurse them. After this, females will go on foraging trips lasting as long as three days, returning to nurse their pups for up to a day. Pups left onshore tend to gather in nurseries to socialize and play. When returning from a trip, females call their pups with distinctive calls to which the pups will reply in kind. A mother and pup can distinguish each other's calls from those of other mothers and pups. At first, reunions largely depend on the efforts of the mothers. However, as pups get older, they get more involved in reunions. Older pups may sometimes join their mothers during their foraging trips. Adult male California sea lions play no role in raising pups, but they do take more interest in them than adult males of other otariid species; they have even been observed to help shield swimming pups from predators. Pups are weaned by a year but can continue to suckle for another year.


Communication

California sea lions communicate with a range of vocalizations. The most commonly used one is their characteristic bark. Territorial males are the loudest and most continuous callers, and barks are produced constantly during the peak of the breeding season. California sea lions bark especially rapidly when excited. The barks of territorial and non-territorial males sound similar, although those of the former are deeper. Males may bark when threatening other males or during courtship. The only other vocalization made by territorial males is a "prolonged hoarse grunt sound" made when an individual is startled by a human. This vocalization is also made by groups of non-reproductive males. Female California sea lions are less vocal. Their barks, high-pitched and shorter than those made by males, are used in aggressive situations. Other aggressive vocalizations given by females include the "squeal", the "belch", and the "growl". The sound a female California sea lion gives when calling her pups is called a "pup-attraction call", described as "loud" and "brawling". Pups respond with a "mother-response call", which is similar in structure. Pups will also bleat or bark when playing or in distress. California sea lions can produce vocalizations underwater. These include "whinny" sounds, barks, buzzings, and clicks.


Nonbreeding activities

Outside the breeding season, males migrate to the northern ends of the species range to feed, while females forage near the breeding rookeries. California sea lions can stay at sea for as long as two weeks at a time. They make continuous dives, returning to the surface to rest. California sea lions may travel alone or in groups while at sea and haul-out between each sea trip. Adult females and juveniles molt in autumn and winter; adult males molt in January and February. California sea lions in the Gulf of California do not migrate; they stay in the Gulf of California year-round.


Intelligence and trainability

Marine biologist Ronald J. Schusterman and his research associates have studied the California sea lions' cognitive ability. They have discovered that California sea lions are able to recognize relationships between
stimuli A stimulus is something that causes a physiological response. It may refer to: * Stimulation ** Stimulus (physiology), something external that influences an activity ** Stimulus (psychology), a concept in behaviorism and perception * Stimulus (eco ...
based on similar functions or connections made with their peers, rather than only the stimuli's common features. California sea lions have demonstrated the ability to understand simple syntax and commands when taught an artificial
sign language Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning, instead of spoken words. Sign languages are expressed through manual articulation in combination with non-manual markers. Sign l ...
. However, California sea lions rarely used the signs semantically or logically. In 2011, a California sea lion named Ronan was recorded bobbing her head in synchronization to musical rhythms. This "rhythmic entrainment" was previously seen only in humans, parrots and other birds possessing vocal mimicry. Because of their intelligence and trainability, California sea lions have been used by
circus A circus is a company of performers who put on diverse entertainment shows that may include clowns, acrobats, trained animals, trapeze acts, musicians, dancers, hoopers, tightrope walkers, jugglers, magicians, ventriloquists, and unicyclist ...
es and
marine mammal park A marine mammal park (also known as marine animal park and sometimes oceanarium) is a commercial theme park or aquarium where marine mammals such as dolphins, beluga whales and sea lions are kept within water tanks and displayed to the public in ...
s to perform various tricks such as throwing and catching balls on their noses, running up ladders, or honking horns in a musical fashion. Trainers reward their animals with fish, which motivates them to perform. For ball balancing, trainers toss a ball at a California sea lion so it may accidentally balance it or hold the ball on its nose, thereby gaining an understanding of what to do. A California sea lion may go through a year of training before performing a behavior for the public. However, its memory allows it to perform a behavior even after three months of resting. Some organizations, such as the
Humane Society of the United States The Humane Society of the United States (HSUS) is an American nonprofit organization that focuses on animal welfare and opposes animal-related cruelties of national scope. It uses strategies that are beyond the abilities of local organizations. ...
and
World Animal Protection World Animal Protection, formerly The World Society for the Protection of Animals (WSPA) is an international non-profit animal rights organization that has been in operation since 1981. The charity describes its vision as: A world where animal ...
, object to using California sea lions and other marine mammals for entertainment, claiming the tricks are "exaggerated variations of their natural behaviors" and distract the audience from the animal's unnatural environment. The California sea lion is used in
military applications Military science is the study of military processes, institutions, and behavior, along with the study of warfare, and the theory and application of organized coercive force. It is mainly focused on theory, method, and practice of producing mil ...
by the
U.S. Navy Marine Mammal Program The U.S. Navy Marine Mammal Program (NMMP) is a program administered by the U.S. Navy which studies the military use of marine mammals - principally bottlenose dolphins and California sea lions - and trains animals to perform tasks such as ship an ...
, including detecting
naval mine A naval mine is a self-contained explosive device placed in water to damage or destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, any ...
s and enemy divers. In the
Persian Gulf The Persian Gulf ( fa, خلیج فارس, translit=xalij-e fârs, lit=Gulf of Persis, Fars, ), sometimes called the ( ar, اَلْخَلِيْجُ ٱلْعَرَبِيُّ, Al-Khalīj al-ˁArabī), is a Mediterranean sea (oceanography), me ...
, the animals can swim behind divers approaching a US naval ship and attach a clamp with a rope to the diver's leg. Navy officials say California sea lions can do this in seconds, before the enemy realizes what happened. Organizations like
PETA Peta or PETA may refer to: Acronym * Pembela Tanah Air, a militia established by the occupying Japanese in Indonesia in 1943 * People for the Ethical Treatment of Animals, an American animal rights organization * People Eating Tasty Animals, an ...
believe that such operations put the animals in danger. However, the Navy insists that California sea lions are removed once their mission is complete.


Status

The
IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
lists the California sea lion as Least Concern due to "its large and increasing population size." The estimated population is 238,000–241,000 for the U.S. or Pacific Temperate stock, 75,000–85,000 for the Western Baja California or Pacific Tropical stock, and 31,393 for the population in the Gulf of California. Off the
Pacific coast of the United States The West Coast of the United States, also known as the Pacific Coast, Pacific states, and the western seaboard, is the coastline along which the Western United States meets the North Pacific Ocean. The term typically refers to the Contiguous Unit ...
, California sea lions are so numerous that they are close to
carrying capacity The carrying capacity of an environment is the maximum population size of a biological species that can be sustained by that specific environment, given the food, habitat, water, and other resources available. The carrying capacity is defined as t ...
, while the Gulf of California population declined by 20% by 2008. California sea lions may be killed when in conflict with
fishermen A fisher or fisherman is someone who captures fish and other animals from a body of water, or gathers shellfish. Worldwide, there are about 38 million commercial and subsistence fishers and fish farmers. Fishers may be professional or recreat ...
, by
poaching Poaching has been defined as the illegal hunting or capturing of wild animals, usually associated with land use rights. Poaching was once performed by impoverished peasants for subsistence purposes and to supplement meager diets. It was set a ...
, and by entanglements in man-made garbage. They are also threatened by pollutants like
DDT Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. ...
and
PCB PCB may refer to: Science and technology * Polychlorinated biphenyl, an organic chlorine compound, now recognized as an environmental toxin and classified as a persistent organic pollutant * Printed circuit board, a board used in electronics * ...
which accumulate in the marine food chain. In the United States, the California sea lion is protected on the federal
Marine Mammal Protection Act The Marine Mammal Protection Act (MMPA) was the first act of the United States Congress to call specifically for an ecosystem approach to wildlife management. Authority MMPA was signed into law on October 21, 1972, by President Richard Nixon ...
(MMPA), passed in 1972, which outlaws hunting, killing, capture, and harassment of the animal. In 1994 an amendment to the Act allowed for the possibility of limited lethal removal of pinnipeds preying on endangered salmonids should the level of predation be documented to have a significant adverse impact on the decline or recovery of ESA-listed salmonids. Applications have been granted for removal of several individual California sea lions at Ballard Locks and at the Bonneville Dam, where up to 92 California sea lions can be killed each year for a 5-year period. Wildlife officials have unsuccessfully attempted to ward off the sea lions using
bomb A bomb is an explosive weapon that uses the Exothermic process, exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-t ...
s,
rubber bullet Rubber bullets (also called rubber baton rounds) are a type of baton round. Despite the name, rubber bullets typically have either a metal core with a rubber coating, or are a homogeneous admixture with rubber being a minority component. Altho ...
s and
bean bags A bean bag (also beanbag) is a sealed bag containing dried beans, Polyvinyl chloride, PVC pellets, expanded polystyrene, or expanded polypropylene. The bags are commonly used for throwing games, but they have various other applications. Furniture ...
. Efforts to chase sea lions away from the area have also proven ineffective. Critics have objected to the killing of the California sea lions, pointing out that the level of mortality permitted as a result of recreational and commercial fisheries in the river and as part of the operation of
hydroelectric dams Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined an ...
pose a greater threat to the salmon. These animals exploit more man-made environments like docks for haul-out sites. Many docks are not designed to withstand the weight of several resting California sea lions which cause major tilting and other problems. Wildlife managers have used various methods to control the animals and some city officials have redesigned docks so they can better withstand them.


2015 Californian shore sea lions pups crisis

In January and February 2015, 1450 malnourished or sick California sea lion pups were found along stretches of the California coast, and estimations give a higher number of dead pups. The
National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...
has pointed to unprecedentedly warm Pacific coastal waters, related to
Pacific decadal oscillation The Pacific decadal oscillation (PDO) is a robust, recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N. O ...
and
El Niño El Niño (; ; ) is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (approximately between the International Date L ...
, as the likely cause. Elevated water temperatures reduced the abundance of anchovies, sardines and mackerel, principal components of the California sea lion pup diet during nursery season. This caused many California sea lion pups to starve, while others died when they took to open waters in search of food at too early an age. Several months earlier, in the summer of 2014, a large number of Cassin's auklet chicks died during the fledging period due to similar circumstances brought about by elevated water temperatures.


Oregon and Washington state governments annual killings

In November 2018, the State of Oregon obtained a permit to kill 93 California sea lions per year below Willamette Falls. Under a similar program, Oregon and Washington had killed over 150 California sea lions on the Columbia River by January 2019.


References


External links

*
WDFW Fact Sheet on sea lionsUSACE information on sea lion deterrentsSmithsonian Institution – North American Mammals: Zalophus californianus
* {{Taxonbar, from=Q379732 Zalophus Pinnipeds of North America Western North American coastal fauna Mammals of Canada Mammals of Mexico Mammals of the United States Fauna of the Western United States Fauna of Gulf of California islands Fauna of California Fauna of the San Francisco Bay Area Mammals described in 1828 Taxa named by René Lesson Articles containing video clips Least concern biota of the United States Least concern biota of North America