Steller's Sea Lion - AbsoluteAstronomy.com

The Steller sea lion also known as the northern sea lion, is a threatened species of sea lion

Sea Lion

Sea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...

in the northern Pacific. It is the sole member of the genus Eumetopias and the largest of the eared seal

Eared Seal

The eared seals or otariids are marine mammals in the family Otariidae, one of three groupings of Pinnipeds. They comprise 16 species in seven genera commonly known either as sea lions or fur seals, distinct from true seals and the Walrus...

s (Otariidae). Among pinnipeds, it is inferior in size only to the walrus

Walrus

The walrus is a large flippered marine mammal with a discontinuous circumpolar distribution in the Arctic Ocean and sub-Arctic seas of the Northern Hemisphere. The walrus is the only living species in the Odobenidae family and Odobenus genus. It is subdivided into three subspecies: the Atlantic...

and the two elephant seal

Elephant seal

Elephant seals are large, oceangoing seals in the genus Mirounga. There are two species: the northern elephant seal and the southern elephant seal . Both were hunted to the brink of extinction by the end of the 19th century, but numbers have since recovered...

s. The species is named for the naturalist Georg Wilhelm Steller

Georg Wilhelm Steller

Georg Wilhelm Steller was a German botanist, zoologist, physician and explorer, who worked in Russia and is considered the discoverer of Alaska and a pioneer of Alaskan natural history.-Biography:...

who first described them in 1741. The Steller sea lion has attracted considerable attention in recent decades due to significant, unexplained declines in their numbers over a large portion of their range in Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

Physical description

Adult animals are lighter in color than most sea lions, ranging from pale yellow to tawny and occasionally reddish. Steller sea lion pups are born almost black, weighing around 23 kg (50 lbs), and remain dark for several months. Females and males both grow rapidly until the fifth year, after which female growth slows down considerably, attaining on average 2.5 m (8 feet) in length and 300 kg (660 lbs). Males continue to grow until their secondary sexual traits

Secondary sex characteristic

Secondary sex characteristics are features that distinguish the two sexes of a species, but that are not directly part of the reproductive system. They are believed to be the product of sexual selection for traits which give an individual an advantage over its rivals in courtship and aggressive...

appear in their fifth to eighth year. Males are slightly longer than the females; they grow to about 2.82–3.25 m (9.2–10.7 feet) long and have much wider chests, necks and general forebody structure and weigh 544–1100 kg (1200–2500 lbs). Males are further distinguished by broader, higher foreheads, flatter snouts, and darker, slightly tuftier hair around their large necks, giving them a maned appearance. Indeed, their Latin name translates roughly as: "maned one with the broad forehead".

Ecology

The range

Range (biology)

In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...

of the Steller sea lion extends from the Kuril Islands

Kuril Islands

The Kuril Islands , in Russia's Sakhalin Oblast region, form a volcanic archipelago that stretches approximately northeast from Hokkaidō, Japan, to Kamchatka, Russia, separating the Sea of Okhotsk from the North Pacific Ocean. There are 56 islands and many more minor rocks. It consists of Greater...

and the Sea of Okhotsk

Sea of Okhotsk

The Sea of Okhotsk is a marginal sea of the western Pacific Ocean, lying between the Kamchatka Peninsula on the east, the Kuril Islands on the southeast, the island of Hokkaidō to the far south, the island of Sakhalin along the west, and a long stretch of eastern Siberian coast along the west and...

in Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

to the Gulf of Alaska

Gulf of Alaska

The Gulf of Alaska is an arm of the Pacific Ocean defined by the curve of the southern coast of Alaska, stretching from the Alaska Peninsula and Kodiak Island in the west to the Alexander Archipelago in the east, where Glacier Bay and the Inside Passage are found.The entire shoreline of the Gulf is...

in the north, and down to Año Nuevo Island

Año Nuevo Island

Año Nuevo Island is a small island off Año Nuevo Point on the coast of Northern California, between San Francisco and Santa Cruz. It is an important breeding site for Northern Elephant Seals and the endangered Steller's Sea Lion, as well as several species of seabirds, including Rhinoceros...

off central California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

. They formerly bred as far south as the Channel Islands

Channel Islands of California

The Channel Islands of California are a chain of eight islands located in the Pacific Ocean off the coast of Southern California along the Santa Barbara Channel in the United States of America...

but have not been observed there since the 1980s. Based on genetic anаlyses and local migration patterns, the global Steller sea lion population has traditionally been divided into an Eastern and Western stock at 144° W longitude, roughly through the middle of the Gulf of Alaska. Recent evidence suggests that the sea lions in Russia in the Sea of Okhotsk

Sea of Okhotsk

and the Kuril islands

Kuril Islands

comprise a third Asian stock, while the sea lions on the eastern seaboard of Kamchatka and the Commander Islands belong to the Western stock

In the summer period, Steller sea lions tend to shift their range somewhat southward. Thus, though there are no reproductive rookeries in Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, there are several consistent haulouts

Hauling-out

Hauling-out is the behaviour associated with pinnipeds , of temporarily leaving the water between periods of foraging activity for sites on land or ice...

around Hokkaidō

Hokkaido

, formerly known as Ezo, Yezo, Yeso, or Yesso, is Japan's second largest island; it is also the largest and northernmost of Japan's 47 prefectural-level subdivisions. The Tsugaru Strait separates Hokkaido from Honshu, although the two islands are connected by the underwater railway Seikan Tunnel...

in the winter and spring.

Steller sea lions are skilled and opportunistic marine predators feeding on a wide range of fish and cephalopod

Cephalopod

A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

species. Important diet components include walleye pollock

Pollock

Pollock is the common name used for either of the two species of marine fish in the Pollachius genus. Both P. pollachius and P. virens are commonly referred to as pollock. Other names for P...

, Atka mackerel

Mackerel

Mackerel is a common name applied to a number of different species of fish, mostly, but not exclusively, from the family Scombridae. They may be found in all tropical and temperate seas. Most live offshore in the oceanic environment but a few, like the Spanish mackerel , enter bays and can be...

, halibut

Halibut

Halibut is a flatfish, genus Hippoglossus, from the family of the right-eye flounders . Other flatfish are also called halibut. The name is derived from haly and butt , for its popularity on Catholic holy days...

, herring

Herring

Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...

, capelin

Capelin

The capelin or caplin, Mallotus villosus, is a small forage fish of the smelt family found in the Atlantic and Arctic oceans. In summer, it grazes on dense swarms of plankton at the edge of the ice shelf. Larger capelin also eat a great deal of krill and other crustaceans...

, flatfish

Flatfish

The flatfish are an order of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating through and around the head during development...

Pacific cod

Pacific Cod

The Pacific cod, Gadus macrocephalus, is an important commercial food species. It is also known as gray cod, gray goo, gray wolf, grayest or grayfish. It has three separate dorsal fins, and the catfish-like whiskers on its lower jaw. In appearance, it is similar to the Atlantic Cod...

, rockfish

Sebastes

Sebastes is a genus of fish in the family Sebastidae , most of which have the common name of rockfish. Most of the world's almost 110 Sebastes species live in the north Pacific, although two live in the south Pacific/Atlantic and four Sebastes is a genus of fish in the family Sebastidae (though...

, sculpins, and cephalopods. They seem to prefer schooling fish and remain primarily in between inter-tidal zones and continental shelves

Continental shelf

The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...

. They are also known to enter estuarine environments and feed on some semi-freshwater fish like sturgeon

Sturgeon

Sturgeon is the common name used for some 26 species of fish in the family Acipenseridae, including the genera Acipenser, Huso, Scaphirhynchus and Pseudoscaphirhynchus. The term includes over 20 species commonly referred to as sturgeon and several closely related species that have distinct common...

. Very occasionally, they have been known to predate on Northern fur seal

Northern Fur Seal

The Northern fur seal is an eared seal found along the north Pacific Ocean, the Bering Sea and the Sea of Okhotsk. It is the largest member of the fur seal subfamily and the only species in the genus Callorhinus.-Physical description:Northern fur seals have extreme sexual dimorphism, with males...

, harbor seal

Harbor Seal

The harbor seal , also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere...

and sea otter

Sea Otter

The sea otter is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Adult sea otters typically weigh between 14 and 45 kg , making them the heaviest members of the weasel family, but among the smallest marine mammals...

pups. They are near the top of the marine food chain

Food chain

A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

but are susceptible to predation by killer whales and white sharks.

Reproductive behavior and life history

Reproductively mature male sea lions aggregate in May on traditional, well-defined reproductive rookeries

Rookery

A rookery is a colony of breeding animals, generally birds. A rook is a Northern European and Central Asian member of the crow family, which nest in prominent colonies at the tops of trees. The term is applied to the nesting place of birds, such as crows and rooks, the source of the term...

, usually on beaches on isolated islands. The larger, older males establish and defend distinct territories on the rookery. A week or so later, adult females arrive, accompanied occasionally by sexually immature offspring, and form fluid aggregations throughout the rookery. Like all other otariids, Steller sea lions are polygynous. However, unlike some other species, they do not coerce individual females into harems but control spatial territories among which females freely move about. Steller sea lions have use three types of territories; aquatic, semi-aquatic and terrestrial. Males with semi-aquatic territories have the most success in defending them. The boundaries of territories are defined by natural features such as rocks, faults or ridges in rocks. Territories can remain stable for 60 days.

Pregnant females give birth soon after arriving on a rookery, and copulation generally occurs one to two weeks after giving birth, but the fertilized egg does not become implanted in the uterus until the fall. Twins are rare. After a week or so of nursing without leaving the rookery, females begin to take progressively longer and more frequent foraging trips leaving their pups behind, until at some point in late summer the mother and pup both leave the rookery. Reproductive males fast throughout the reproductive season, often without entering the water once from mid-May until August, at which point the structure of the reproductive rookeries begins to fall apart and most animals leave for the open seas and disperse throughout their range.

Age at weaning is highly variable, pups may remain with their mothers for as long as 4 years. Incidents of mothers feeding daughters who are simultaneously feeding their own newborn pups have been documented, an extremely rare occurrence among mammals.

Interactions with humans

Steller sea lion were hunted for meat and other commodities by prehistoric communities everywhere their range intersected with human communities. Aside from food and clothing, their skin was notably used to cover baidarka

Baidarka

Baidarka is the Russian name used for Aleutian style sea kayak. The ancient Unangan name is Iqyax. The word has its origins from early Russian settlers in Alaska. Iqya-x builders who kept the tradition of building skin-on-skeleton boats alive in the 20th century include Sergie Sovoroff.A prominent...

s and kayaks. A subsistence harvest on the order of 300 animals or less continues to this day in some native communities in Alaska.

Historically, the sea lion has had only very slight commercial value. For example, in the 19th century their whisker

Whisker

Whisker may refer to:* an element of box plots* cat's whisker diode, a thin wire used as a contact on a crystal radio receiver* facial hair, hair on the face of a human* vibrissa, a hair on the face of a mammal, used for sensing the surroundings...

s sold for a penny apiece for use as tobacco-pipe cleaner

Pipe cleaner

A pipe cleaner or chenille stem is a type of brush originally intended for cleaning dottle from smoking pipes. Besides cleaning pipes, they can be used for any application that calls for cleaning out small bores or tight places. Special pipe cleaners are manufactured specifically for cleaning out...

s. Their penises are considered to be aphrodisiacs in some forms of traditional Chinese medicine

Traditional Chinese medicine

Traditional Chinese Medicine refers to a broad range of medicine practices sharing common theoretical concepts which have been developed in China and are based on a tradition of more than 2,000 years, including various forms of herbal medicine, acupuncture, massage , exercise , and dietary therapy...

.

Steller sea lions are sometimes killed intentionally by fishermen as they are seen as competitors and a threat to fish stocks. Killing sea lions is strictly prohibited in the U.S, Canada and Russia, but in Japan, a fixed number are still removed annually ostensibly to protect their fisheries.

In recent years, Steller sea lions have been known to enter the Columbia River

Columbia River

The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...

estuary and feed on white sturgeon

White sturgeon

The white sturgeon , also known as the Pacific sturgeon, Oregon sturgeon, Columbia sturgeon, Sacramento sturgeon, and California white sturgeon, is a sturgeon which lives along the west coast of North America from the Aleutian Islands to Central...

, several salmon species and rainbow trout

Rainbow trout

The rainbow trout is a species of salmonid native to tributaries of the Pacific Ocean in Asia and North America. The steelhead is a sea run rainbow trout usually returning to freshwater to spawn after 2 to 3 years at sea. In other words, rainbow trout and steelhead trout are the same species....

, some of which are also listed under the U.S. Endangered Species Act

Endangered Species Act

The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...

. They enter the Columbia River primarily in the late winter and spring, occasionally going as far upstream as Bonneville Dam

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, in the Columbia River Gorge. The primary functions of...

. Though not as abundant as the California sea lion

California Sea Lion

The California sea lion is a coastal sea lion of western North America. Their numbers are abundant , and the population continues to expand about 5% annually. They are quite intelligent and can adapt to man-made environments...

, they are still a concern for those agencies charged with managing the fish populations. Since the Steller sea lions are themselves protected under the Marine Mammal Protection Act

Marine Mammal Protection Act

The Marine Mammal Protection Act of 1972 was the first article of legislation to call specifically for an ecosystem approach to natural resource management and conservation. MMPA prohibits the taking of marine mammals, and enacts a moratorium on the import, export, and sale of any marine mammal,...

, managers are compelled to use non-lethal deterrence methods such as rubber bullets and noisemakers. Deterrence by the public is strictly forbidden.

Recent decline

While the populations of the eastern and Asian stocks appear stable, the population in the western stock, particularly along the Aleutian Islands, was estimated to have fallen by 70–80% since the 1970s. As a consequence, in 1990 the western stock of Steller sea lions was listed as endangered and the eastern stock was listed as threatened under the Endangered Species Act

Endangered Species Act

. They have since been the object of intense study and the focus of much political and scientific debate in Alaska

Alaska

.

One suspected cause of their precipitous decline is overfishing of Alaska pollock

Alaska pollock

Alaska pollock or walleye pollock is a North Pacific species of the cod family Gadidae. While related to the common Atlantic pollock species of the same family, the Alaska pollock is not a member of the same Pollachius genus.The Norwegian pollock , a rare fish of Norwegian waters, may actually be...

, herring

Herring

, and other fish stocks in the Gulf of Alaska. Other hypotheses include increased predation by orca

Orca

The killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...

s, indirect effects of prey species composition shifts due to changes in climate, effects of disease or contaminants, shooting by fishermen, and others. The decline is certainly due to a complex of interrelated factors which have yet to be definitively teased apart by the research effort.

External links

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