Sea Otter
Encyclopedia
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
(30 to 100 lb
), making them the heaviest members of the weasel family
, but among the smallest marine mammals. Unlike most marine mammals, the sea otter's primary form of insulation is an exceptionally thick coat of fur
, the densest in the animal kingdom. Although it can walk on land, the sea otter lives mostly in the ocean.
The sea otter inhabits offshore environments where it dives to the sea floor to forage
. It preys mostly upon marine invertebrates such as sea urchin
s, various molluscs and crustacean
s, and some species of fish
. Its foraging and eating habits are noteworthy in several respects. First, its use of rocks to dislodge prey and to open shells makes it one of the few mammal species to use tools. In most of its range, it is a keystone species
, controlling sea urchin populations which would otherwise inflict extensive damage to kelp forest
ecosystem
s. Its diet includes prey species that are also valued by humans as food, leading to conflicts between sea otters and fisheries.
Sea otters, whose numbers were once estimated at 150,000–300,000, were hunted extensively for their fur between 1741 and 1911, and the world population fell to 1,000–2,000 individuals in a fraction of their historic range. A subsequent international ban on hunting, conservation efforts, and reintroduction programs into previously populated areas have contributed to numbers rebounding, and the species now occupies about two-thirds of its former range. The recovery of the sea otter is considered an important success in marine conservation
, although populations in the Aleutian Islands and California
have recently declined or have plateaued at depressed levels. For these reasons (as well as its particular vulnerability to oil spill
s) the sea otter remains classified as an endangered species
.
of 1758. Originally named Lutra marina, it underwent numerous name changes before being accepted as Enhydra lutris in 1922. The generic name Enhydra, derives from the Ancient Greek
en/εν "in" and hydra/ύδρα "water", meaning "in the water", and the Latin
word lutris, meaning "otter". It was formerly sometimes referred to as the "sea beaver", although it is only distantly related to beaver
s. It is not to be confused with the marine otter
, a rare otter species native to the southern west coast of South America. A number of other otter species, while predominantly living in fresh water, are commonly found in marine coastal habitats. The extinct sea mink
of northeast North America is another mustelid that adapted to a marine environment.
The sea otter is the heaviest member of the family Mustelidae
, a diverse group that includes the thirteen otter
species and terrestrial animals such as weasel
s, badger
s, and mink
s. It is unique among the mustelids in not making dens or burrow
s, in having no functional anal scent glands, and in being able to live its entire life without leaving the water. The only member of the genus Enhydra, the sea otter is so different from other mustelid species that as recently as 1982, some scientists believed it was more closely related to the earless seal
s. Genetic
analysis indicates that the sea otter and its closest extant relatives, which include the African speckle-throated otter
, Eurasian otter, African clawless otter
and oriental small-clawed otter
, shared an ancestor approximately 5 million years ago (mya).
Fossil evidence indicates that the Enhydra lineage became isolated in the North Pacific approximately 2 mya, giving rise to the now-extinct Enhydra macrodonta and the modern sea otter, Enhydra lutris. The sea otter evolved initially in northern Hokkaidō
and Russia, and then spread east to the Aleutian Islands, mainland Alaska
, and down the North American coast. In comparison to cetacea
ns, sirenians, and pinniped
s, which entered the water approximately 50 mya, 40 mya, and 20 mya, respectively, the sea otter is a relative newcomer to a marine existence. In some respects, however, the sea otter is more fully aquatically adapted than pinnipeds, which must haul out on land or ice to give birth.
The reintroduction effort off the Oregon coast was not successful. However, reintroductions in 1969 and 1970 off the Washington coast were very successful and sea otters have been expanding their range since. They have now entered the Strait of Juan de Fuca
and can be found almost as far east as Pillar Point. Individuals have even been seen in the San Juan Islands and northern Puget Sound.
The sea otter is one of the smallest marine mammal
species but is the heaviest mustelid. Male sea otters usually 22 to 45 kg (49 to 99 lb) and are 1.2 to 1.5 m
(4 to 5 ft) in length, though specimens to 54 kg (119 lb) have been recorded. Females are smaller, weighing 14 to 33 kg (30 to 73 lb) and measuring 1.0 to 1.4 m (3 ft 3 in to 4 ft 7 in) in length. Its baculum
is, for the male otter's size, very large, massive and bent upwards, measuring 150 mm (6 in) in length and 15 mm wide (0.6 in) at the base.
Unlike other marine mammals, the sea otter has no blubber
and relies on its exceptionally thick fur to keep warm. With up to 150,000 strands of hair per square centimeter (nearly one million per sq in), its fur
is the most dense of any animal. The fur consists of long waterproof guard hairs and short underfur; the guard hairs keep the dense underfur layer dry. Cold water is thus kept completely away from the skin and heat loss is limited. The fur is thick year-round, as it is shed and replaced gradually rather than in a distinct molting season. As the ability of the guard hairs to repel water depends on utmost cleanliness, the sea otter has the ability to reach and groom the fur on any part of its body, taking advantage of its loose skin and an unusually supple skeleton
. The coloration of the pelage is usually deep brown with silver-gray speckles, but it can range from yellowish or grayish brown to almost black. In adults, the head, throat, and chest are lighter in color than the rest of the body.
The sea otter displays numerous adaptations to its marine environment. The nostrils and small ears can close. The hind feet, which provide most of its propulsion in swimming, are long, broadly flattened, and fully webbed. The fifth digit on each hind foot is longest, facilitating swimming while on its back, but making walking difficult. The tail is fairly short, thick, slightly flattened, and muscular. The front paws are short with retractable claws, with tough pads on the palms that enable gripping slippery prey.
The sea otter propels itself underwater by moving the rear end of its body, including its tail and hind feet, up and down, and is capable of speeds of up to 9 km/h (5.6 mph). When underwater, its body is long and streamlined, with the short forelimbs pressed closely against the chest. When at the surface, it usually floats on its back and moves by sculling its feet and tail from side to side. At rest, all four limbs can be folded onto the torso to conserve heat, whereas on particularly hot days the hind feet may be held underwater for cooling. The sea otter's body is highly buoyant because of its large lung capacity – about 2.5 times greater than that of similar-sized land mammals – and the air trapped in its fur. The sea otter walks with a clumsy rolling gait on land, and can run in a bounding motion.
Long, highly sensitive whiskers and front paws help the sea otter find prey by touch when waters are dark or murky. Researchers have noted that when they approach in plain view, sea otters react more rapidly when the wind is blowing towards the animals, indicating that the sense of smell
is more important than sight
as a warning sense. Other observations indicate that the sea otter's sense of sight is useful above and below the water, although not as good as that of seals. Its hearing
is neither particularly acute nor poor.
An adult's 32 teeth, particularly the molars
, are flattened and rounded, designed to crush rather than cut food. Seals
and sea otters are the only carnivore
s with two pairs of lower incisor
teeth rather than three; the adult dental formula
is
The sea otter has a metabolic rate two or three times that of comparatively sized terrestrial
mammals. It must eat an estimated 25 to 38% of its own body weight in food each day in order to burn the calories necessary to counteract the loss of heat due to the cold water environment. Its digestive efficiency is estimated at 80 to 85%, and food is digested and passed in as little as three hours. Most of its need for water is met through food, although, in contrast to most other marine mammals, it also drinks seawater. Its relatively large kidney
s enable it to derive fresh water from sea water and excrete concentrated urine.
The sea otter is diurnal. It has a period of foraging and eating in the morning, starting about an hour before sunrise, then rests or sleeps in mid-day. Foraging resumes for a few hours in the afternoon and subsides before sunset, and there may be a third foraging period around midnight. Females with pups appear to be more inclined to feed at night. Observations of the amount of time a sea otter must spend each day foraging range from 24 to 60%, apparently depending on the availability of food in the area.
The sea otter spends much of its time grooming, which consists of cleaning the fur, untangling knots, removing loose fur, rubbing the fur to squeeze out water and introduce air, and blowing air into the fur. To an observer it appears as if the animal is scratching, however sea otters are not known to have lice or other parasites in the fur. When eating, the sea otter rolls in the water frequently, apparently to wash food scraps from its fur.
s and other organisms from kelp and dig deep into underwater mud for clam
s. It is the only marine mammal that catches fish
with its forepaws rather than with its teeth.
Under each foreleg, the sea otter has a loose pouch of skin that extends across the chest. In this pouch (preferentially the left one), the animal stores collected food to bring to the surface. In this pouch they also keep a rock unique to each otter that is used to break open shellfish and clams. There, the sea otter eats while floating on its back, using its forepaws to tear food apart and bring it to its mouth. It can chew and swallow small mussel
s with their shells, whereas large mussel shells may be twisted apart. It uses its lower incisor
teeth to access the meat in shellfish.
To eat large sea urchins, which are mostly covered with spines, the sea otter bites through the underside where the spines are shortest, and licks the soft contents out of the urchin's shell.
The sea otter's use of rocks when hunting and feeding makes it one of the few mammal
species to use tools. To open hard shells, it may pound its prey with both paws against a rock on its chest. To pry an abalone
off its rock, it hammers the abalone shell using a large stone, with observed rates of 45 blows in 15 seconds. Releasing an abalone, which can cling to rock with a force equal to 4,000 times its own body weight, requires multiple dives.
.
A male sea otter is most likely to mate if he maintains a breeding territory in an area that is also favored by females. As autumn is the peak breeding season in most areas, males typically defend their territory only from spring to autumn. During this time, males patrol the boundaries of their territories to exclude other males, although actual fighting is rare. Adult females move freely between male territories, where they outnumber adult males by an average of five to one. Males who do not have territories tend to congregate in large male-only groups, and swim through female areas when searching for a mate.
The species exhibits a variety of vocal behaviors. The cry of a pup is often compared to that of a seagull. Females coo when they are apparently content; males may grunt instead. Distressed or frightened adults may whistle, hiss, or in extreme circumstances, scream.
Although sea otters can be playful and sociable, they are not considered to be truly social animal
s. They spend much time alone, and each adult can meet its own needs in terms of hunting, grooming, and defense.
Sea otters are polygynous: males have multiple female partners. However, temporary pair-bonding occurs for a few days between a female in estrus and her mate. Mating takes place in the water and can be rough, the male biting the female on the muzzle – which often leaves scars on the nose – and sometimes holding her head under water.
Births occur year-round, with peaks between May and June in northern populations and between January and March in southern populations. Gestation
appears to vary from four to twelve months, as the species is capable of delayed implantation followed by four months of pregnancy. In California, sea otters usually breed every year, about twice as often as sea otters in Alaska.
Birth usually takes place in the water and typically produces a single pup weighing 1.4 to 2.3 kg (3 to 5 lb). Twins occur in 2% of births; however, usually only one pup survives. At birth, the eyes are open, ten teeth are visible, and the pup has a thick coat of baby fur. Mothers have been observed to lick and fluff a newborn for hours; after grooming, the pup's fur retains so much air that the pup floats like a cork and cannot dive. The fluffy baby fur is replaced by adult fur after about thirteen weeks.
Nursing
lasts six to eight months in Californian populations and four to twelve months in Alaska, with the mother beginning to offer bits of prey at one to two months. The milk from a sea otter's two abdominal nipple
s is rich in fat and more similar to the milk of other marine mammals than to that of other mustelids. A pup, with guidance from its mother, practices swimming and diving for several weeks before it is able to reach the sea floor. Initially the objects it retrieves are of little food value, such as brightly colored starfish and pebbles. Juveniles are typically independent at six to eight months, however a mother may be forced to abandon a pup if she cannot find enough food for it and at the other extreme, a pup may nurse until it is almost adult size. Pup mortality is high, particularly during an individual's first winter – by one estimate, only 25% of pups survive their first year. Pups born to experienced mothers have the highest survival rates.
Females perform all tasks of feeding and raising offspring, and have occasionally been observed caring for orphaned pups. Much has been written about the level of devotion of sea otter mothers for their pups – a mother gives her infant almost constant attention, cradling it on her chest away from the cold water and attentively grooming its fur. When foraging, she leaves her pup floating on the water, sometimes wrapped in kelp to keep it from floating away; if the pup is not sleeping, it cries loudly until she returns. Mothers have been known to carry their pup for days after the pup's death.
Females become sexually mature at around three or four years of age and males at around five; however, males often do not successfully breed until a few years later. A captive male sired offspring at age 19. In the wild, sea otters live to a maximum age of 23 years, with average lifespans of 10–15 years for males and 15–20 years for females. Several captive individuals have lived past 20 years, and a female at the Seattle Aquarium
died at the age of 28 years. Sea otters in the wild often develop worn teeth, which may account for their apparently shorter lifespans.
Sea otters live in coastal waters 15 to 23 meters (50 to 75 ft) deep, and usually stay within a kilometer (⅔ mi) of the shore. They are found most often in areas with protection from the most severe ocean winds, such as rocky coastlines, thick kelp forest
s, and barrier reefs. Although they are most strongly associated with rocky substrates
, sea otters can also live in areas where the sea floor consists primarily of mud, sand, or silt. Their northern range is limited by ice, as sea otters can survive amidst drift ice
but not land-fast ice. Individuals generally occupy a home range a few kilometers long, and remain there year-round.
The sea otter population is thought to have once been 150,000 to 300,000, stretching in an arc across the North Pacific from northern Japan to the central Baja California Peninsula
in Mexico. The fur trade that began in the 1740s reduced the sea otter's numbers to an estimated 1,000 to 2,000 members in thirteen colonies. In about two-thirds of its former range, the species is at varying levels of recovery, with high population densities in some areas and threatened
populations in others. Sea otters currently have stable populations in parts of the Russian east coast, Alaska, British Columbia, Washington, and California, and there have been reports of recolonizations in Mexico and Japan. Population estimates made between 2004 and 2007 give a worldwide total of approximately 107,000 sea otters.
. Before the 19th century there were around 20,000 to 25,000 sea otters in the Kuril Islands
, with more on Kamchatka and the Commander Islands. After the years of the Great Hunt, the population in these areas, currently part of Russia, was only 750. As of 2004, sea otters have repopulated all of their former habitat in these areas, with an estimated total population of about 27,000. Of these, about 19,000 are in the Kurils, 2000 to 3500 on Kamchatka and another 5000 to 5500 on the Commander Islands. Growth has slowed slightly, suggesting that the numbers are reaching carrying capacity
.
is the heartland of the sea otter's range. In 1973, the sea otter population in Alaska was estimated at between 100,000 and 125,000 animals. By 2006, however, the Alaska population had fallen to an estimated 73,000 animals. A massive decline in sea otter populations in the Aleutian Islands accounts for most of the change; the cause of this decline is not known, although orca
predation is suspected. The sea otter population in Prince William Sound
was also hit hard by the Exxon Valdez oil spill
, which killed thousands of sea otters in 1989.
in 1929. From 1969 to 1972, 89 sea otters were flown or shipped from Alaska to the west coast of Vancouver Island. This population expanded to over 3,000 as of 2004, and their range on the island's west coast expanded from Cape Scott
in the north to Barkley Sound
to the south. In 1989, a separate colony was discovered in the central British Columbia coast. It is not known if this colony, which had a size of about 300 animals in 2004, was founded by transplanted otters or by survivors of the fur trade.
In 1969 and 1970, 59 sea otters were translocated from Amchitka Island to Washington. Annual surveys between 2000 and 2004 have recorded between 504 and 743 individuals, and their range is in the Olympic Peninsula
from just south of Destruction Island to Pillar Point.
In British Columbia and Washington, sea otters are found almost exclusively on the outer coasts. They can swim as close as 6 feet off shore along the Olympic coast. Reported sightings of sea otters in the San Juan Islands
and Puget Sound
almost always turn out to be northern river otter
s which are commonly seen along the seashore. However, biologists have confirmed isolated sightings of sea otters in these areas since the mid-1990s.
in 1938; their principal range is now from just south of San Francisco to Santa Barbara County. In the late 1980s, the U.S. Fish and Wildlife Service relocated about 140 Californian sea otters to San Nicolas Island
in southern California, in the hope of establishing a reserve population should the mainland be struck by an oil spill. To the surprise of biologists, the San Nicholas population initially shrank as the animals migrated back to the mainland. As of 2005, only 30 sea otters remained at San Nicholas, thriving on the abundant prey around the island. The plan that authorized the translocation program had predicted that carrying capacity would be reached within 5 to 10 years.
When the Fish and Wildlife Service implemented the translocation program, it also attempted to implement "zonal management" of the Californian population. To manage the competition between sea otters and fisheries, it declared an "otter-free zone" stretching from Point Conception
to the Mexican border. In this zone, only San Nicolas Island was designated as sea otter habitat, and sea otters found elsewhere in the area were supposed to be captured and relocated. These plans were abandoned after it proved impractical to capture the hundreds of otters which ignored regulations and swam into the zone. However, after engaging in a period of public commentary in 2005, the Fish and Wildlife Service has yet to release a formal decision on the issue.
Sea otters were once numerous in San Francisco Bay
. Historical records reveal that the Russian-American Company
snuck Aleuts into San Francisco Bay multiple times, despite the Spanish capturing or shooting them while hunting sea otters in the estuaries of San Jose
, San Mateo
, San Bruno
and around Angel Island. The founder of Fort Ross, Ivan Kuskov
, finding otter scarce on his second voyage to Bodega Bay in 1812, sent a party of Aleuts to San Francisco Bay where they met another Russian party and an American party, and caught 1,160 sea otters in three months. By 1817 sea otters in the area were practically eliminated and the Russians sought permission from the Spanish and the Mexican governments to hunt further and further south of San Francisco. Remnant sea otter populations may have survived in the bay until 1840, when the Rancho Punta de Quentin
was granted to Captain John B. R. Cooper, a sea captain from Boston, by Mexican Governor Juan Bautista Alvarado
along with a license to hunt sea otters, reportedly then prevalent at the mouth of Corte Madera Creek
.
Although the southern sea otter's range has continuously expanded from Big Sur since protection in 1911, in the last two years the otter population and its range have contracted. As of spring 2010 the northern boundary has moved from about Tunitas Creek
to a point 2 km southeast of Pigeon Point, and the southern boundary has moved from approximately Coal Oil Point to Gaviota State Park
. Recently a toxin called microcystin
, produced by a type of cyanobacteria (Microcystis), seems to be concentrated in the shellfish that otters eat, poisoning them. Cyanobacteria are found in stagnant freshwater enriched with nitrogen and phosphorus from septic tank and agricultural fertilizer runoff, and may be flushed into the ocean when streamflows are high in the rainy season. A record number of sea otter carcasses were found on California's coastline in 2010, with increased shark attacks an increasing component of the mortality.
In 2004 a lone male sea otter took up residence at Simpson Reef off of Cape Arago for six months. This male is thought to have originated from a colony in Washington, but disappeared after a coastal storm.
The most recent sighting of a sea otter off the Oregon coast took place 18 February 2009, in Depoe Bay, Oregon. The lone male sea otter could have traveled from either California or Washington.
Sea otters consume over 100 different prey species. In most of its range, the sea otter's diet consists almost exclusively of marine invertebrates, including sea urchin
s, a variety of bivalves such as clam
s and mussel
s, abalone
, other mollusks, crustacean
s, and snail
s. Its prey ranges in size from tiny limpet
s and crab
s to giant octopus
es. Where prey such as sea urchins, clams, and abalone are present in a range of sizes, sea otters tend to select larger items over smaller ones of similar type. In California, it has been noted that sea otters ignore Pismo clam
s smaller than 3 inches (7 cm) across.
In a few northern areas, fish are also eaten. In studies performed at Amchitka Island in the 1960s, where the sea otter population was at carrying capacity
, 50% of food found in sea otter stomachs was fish. The fish species were usually bottom-dwelling and sedentary or sluggish forms, such as Hemilepidotus hemilepidotus and family Tetraodontidae. However, south of Alaska on the North American coast, fish are a negligible or extremely minor part of the sea otter's diet. Contrary to popular depictions, sea otters rarely eat starfish, and any kelp
that is consumed apparently passes through the sea otter's system undigested.
The individuals within a particular area often differ in their foraging methods and their prey types, and tend to follow the same patterns as their mothers. The diet of local populations also changes over time, as sea otters can significantly deplete populations of highly preferred prey such as large sea urchins, and prey availability is also affected by other factors such as fishing by humans. Sea otters can thoroughly remove abalone from an area except for specimens in deep rock crevices, however, they never completely wipe out a prey species from an area. A 2007 Californian study demonstrated that in areas where food was relatively scarce, a wider variety of prey was consumed. However, surprisingly, the diets of individuals were more specialized in these areas than in areas where food was plentiful.
; their presence affects the ecosystem more profoundly than their size and numbers would suggest. Sea otters keep the population of certain benthic (sea floor) herbivores, particularly sea urchin
s, in check. Sea urchins graze on the lower stems of kelp
, causing the kelp to drift away and die. Loss of the habitat and nutrients provided by kelp forest
s leads to profound cascade effects
on the marine ecosystem. North Pacific areas that do not have sea otters often turn into urchin barren
s, with abundant sea urchins and no kelp forest.
Reintroduction of sea otters to British Columbia has led to a dramatic improvement in the health of coastal ecosystems, and similar changes have been observed as sea otter populations recovered in the Aleutian and Commander Islands and the Big Sur
coast of California However, some kelp forest ecosystem
s in California have also thrived without sea otters, with sea urchin populations apparently controlled by other factors. The role of sea otters in maintaining kelp forests has been observed to be more important in areas of open coast than in more protected bays and estuaries.
In addition to promoting growth of kelp forests, sea otters can also have a profound effect in rocky areas that tend to be dominated by mussel
beds. They remove mussels from rocks, liberating space for competitive species and thereby increasing the diversity of species in the area.
s and sea lion
s; bald eagle
s also prey on pups by snatching them from the water surface.
On land, young sea otters may face attack from bear
s and coyote
s. In California, bites from shark
s, particularly great white shark
s, have been estimated to cause 10% of sea otter deaths and are one of the reasons the population has not expanded further north. It is believed that the great white shark
is their primary predator and dead sea otters have been found with injuries from shark bites, although there is no evidence that sharks actually eat them.
An exhibit at the San Diego Natural History Museum
states that cat feces from urban runoff carries parasites to the ocean and kills sea otters.
Sea otters have the thickest fur of any mammal. Their beautiful fur is a main target for many hunters.
Archaeological evidence indicates that for thousands of years, indigenous peoples
have hunted sea otters for food and fur. Large-scale hunting, part of the Maritime Fur Trade
, which would eventually kill approximately one million sea otters, began in the 18th century when hunters and traders began to arrive from all over the world to meet foreign demand for otter pelts, which were one of the world's most valuable types of fur.
In the early 18th century, Russians began to hunt sea otters in the Kuril Islands
and sold them to China
. Russia was also exploring the far northern Pacific at this time, and sent Vitus Bering
to map the Arctic coast and find routes from Siberia to North America. In 1741, on his second North Pacific voyage, Bering was shipwrecked off Bering Island
in the Commander Islands, where Bering and many of his crew died. The surviving crew members, which included naturalist Georg Steller, discovered sea otters on the beaches of the island and spent the winter hunting sea otters and gambling with otter pelts. They returned to Siberia having killed nearly 1000 sea otters, and were able to command high prices for the pelts. Thus began what is sometimes called the "Great Hunt", which would continue for another hundred years.
Russian fur-hunting expeditions soon depleted the sea otter populations in the Commander Islands, and by 1745 they began to move on to the Aleutian Islands. The Russians initially traded with the Aleuts inhabitants of these islands for otter pelts, but later enslaved the Aleuts, taking women and children hostage and torturing and killing Aleut men to force them to hunt. Many Aleuts were either murdered by the Russians or died from diseases that the hunters had introduced. The Aleut population was reduced, by the Russians' own estimate, from 20,000 to 2,000. By the 1760s, the Russians had reached Alaska
. In 1799, Emperor Paul I consolidated the rival fur hunting companies into the Russian-American Company
, granting it an Imperial charter and protection, and a monopoly over trade rights and territorial acquisition.
Under Aleksandr I the administration of the merchant-controlled Company was transferred to the Imperial Navy, largely due to the alarming reports by naval officers of native abuse, and in 1818 the indigenous peoples of Alaska were granted civil rights equivalent to a townsman status in the Russian Empire.
Other nations joined in the hunt in the south. Along the coasts of what is now Mexico
and California
, Spanish
explorers bought sea otter pelts from Native Americans
and sold them in Asia. In 1778, British explorer Captain James Cook reached Vancouver Island
and bought sea otter furs from the First Nations people. When Cook's ship later stopped at a Chinese
port, the pelts rapidly sold at high prices, and were soon known as "soft gold". As word spread, people from all over Europe and North America began to arrive in the Pacific Northwest
to trade for sea otter furs.
Russian hunting expanded to the south, initiated by American ship captains, who sub-contracted Russian supervisors and Aleut hunters in what is now Washington, Oregon, and California. Between 1803 and 1846, 72 American ships were involved in the otter hunt in California, harvesting an estimated 40,000 skins and tails, compared to only 13 ships of the Russian-American Company, which reported 5,696 otter skins taken between 1806-1846. In 1812 the Russians founded an agricultural settlement at what is now Fort Ross
in northern California as their southern headquarters.
Eventually, sea otter populations became so depleted that commercial hunting was no longer viable. In the Aleutian Islands, commercial hunting had stopped by 1808, as a conservation measure imposed by the Russian-American Company. Further restrictions were ordered by the Company in 1834. When Russia sold Alaska
to the United States in 1867, the Alaska population had recovered to over 100,000, but Americans resumed hunting and quickly extirpated the sea otter again. Prices rose as the species became rare: During the 1880s, a pelt brought $105 to $165 in the London market, however by 1903 a pelt could be worth as much as $1,125. In 1911, Russia, Japan, Great Britain (for Canada) and the United States signed the Treaty for the Preservation and Protection of Fur Seals
, imposing a moratorium on the harvesting of sea otters. So few remained, perhaps only 1,000–2,000 individuals in the wild, that many believed the species would become extinct
.
During the 20th century, sea otter numbers rebounded in about two-thirds of their historic range, a recovery that is considered one of the greatest successes in marine conservation. However, the IUCN still lists the sea otter as an endangered species
, and describes the significant threats to sea otters as oil pollution, predation by orca
s, poaching
, and conflicts with fisheries – sea otters can drown if entangled in fishing gear. The hunting of sea otters is no longer legal except for limited harvests by indigenous peoples
in the United States. Poaching was a serious concern in the Russian Far East immediately after the collapse of the Soviet Union in 1991, however it has declined significantly with stricter law enforcement and better economic conditions.
The most significant threat to sea otters is oil spill
s. Sea otters are particularly vulnerable, as they rely on their fur to keep warm. When their fur is soaked with oil, it loses its ability to retain air, and the animal quickly dies from hypothermia
. The liver
, kidney
s, and lung
s of sea otters also become damaged after they inhale oil or ingest it when grooming. The Exxon Valdez oil spill
of 24 March 1989 killed thousands of sea otters in Prince William Sound
, and as of 2006 the lingering oil in the area continues to affect the population. Describing the public sympathy for sea otters that developed from media coverage of the event, a U.S. Fish and Wildlife Service spokesperson wrote:
The small geographic ranges of the sea otter populations in California, Washington, and British Columbia mean that a single major spill could be catastrophic for that state or province. Prevention of oil spills and preparation for the rescue of otters in the event of one are major areas of focus for conservation efforts. Increasing the size and the range of sea otter populations would also reduce the risk of an oil spill wiping out a population. However, because of the species' reputation for depleting shellfish resources, advocates for commercial, recreational, and subsistence shellfish harvesting have often opposed allowing the sea otter's range to increase, and there have even been instances of fishermen and others illegally killing them.
In the Aleutian Islands, a massive and unexpected disappearance of sea otters has occurred in recent decades. In the 1980s, the area was home to an estimated 55,000 to 100,000 sea otters, but the population fell to around 6,000 animals by 2000. The most widely accepted, but still controversial, hypothesis is that orcas have been eating the otters. The pattern of sea otter disappearances is consistent with a rise in orca predation, however there has been no direct evidence that orcas prey on sea otters to any significant extent.
Another area of concern is California, where recovery began to fluctuate or decline in the late 1990s. Unusually high mortality rates amongst adult and sub-adult otters, particularly females, have been reported. Necropsies of dead sea otters indicate that diseases, particularly Toxoplasma gondii
infection and acanthocephala
n parasite infection, are a major cause of sea otter mortality in California. The Toxoplasma gondii parasite, which is often fatal to sea otters, is carried by wild and domestic cats and by opossums, and may be transmitted by domestic cat droppings flushed into the ocean via the sewage system. Although it is clear that disease has contributed to the deaths of many of California's sea otters, it is not known why the Californian population is apparently more affected by disease than populations in other areas.
Sea otter habitat is preserved through several protected areas
in the United States
, Russia
and Canada
. In marine protected areas, polluting activities such as dumping of waste and oil drilling are typically prohibited. There are estimated to be more than 1,200 sea otters within the Monterey Bay National Marine Sanctuary
, and more than 500 within the Olympic Coast National Marine Sanctuary
.
, clam
s, and crab
s, are also food sources for humans. In some areas, massive declines in shellfish
harvests have been blamed on the sea otter, and intense public debate has taken place over how to manage the competition between sea otters and humans for seafood.
The debate is complicated by the fact that sea otters have sometimes been held responsible for declines of shellfish stocks that were more likely caused by overfishing
by humans, disease, pollution, and seismic activity. Shellfish declines have also occurred in many parts of the North American Pacific coast that do not have sea otters, and conservationists sometimes note that the existence of large concentrations of shellfish on the coast is a recent development resulting from the fur trade's near-extirpation
of the sea otter. Although many factors affect shellfish stocks, sea otter predation can deplete a fishery to the point that it is no longer commercially viable. There is a consensus among scientists that sea otters and abalone fisheries cannot co-exist in the same area, and the same is likely true for certain other types of shellfish as well.
There are many facets to the interaction between sea otters and the human economy that are not as immediately felt. Sea otters have been credited with contributing to the kelp
harvesting industry via their well-known role in controlling sea urchin populations; kelp is used in the production of diverse food and pharmaceutical products. Although human divers harvest red sea urchin
s both for food and to protect the kelp, sea otters hunt more sea urchin species and are more consistently effective in controlling these populations. The health of the kelp forest ecosystem is significant in nurturing populations of fish, including commercially important fish species. In some areas, sea otters are a popular tourist
attraction, bringing visitors to local hotels, restaurants, and sea otter-watching expeditions.
>
Left: Aleut sea otter amulet
in the form of a mother with pup. Above: Aleut carving of a sea otter hunt on a whalebone spear. Both items are on display at the St. Petersburg Museum of Anthropology and Ethnography. Articles depicting sea otters were considered to have magical properties.
For many maritime indigenous cultures throughout the North Pacific, especially the Ainu
in the Kuril Islands, the Koryaks
and Itelmen of Kamchatka, the Aleut in the Aleutian Islands and a host of tribes on the Pacific coast of North America
, the sea otter has played an important role as a cultural as well as material resource. In these cultures, many of which have strongly animist traditions full of legends and stories in which many aspects of the natural world are associated with spirits, the sea otter was considered particularly kin to humans. The Nuu-chah-nulth, Haida, and other First Nations
of coastal British Columbia used the warm and luxurious pelts as chiefs' regalia. Sea otter pelts were given in potlatch
es to mark coming-of-age ceremonies, weddings, and funerals. The Aleuts carved sea otter bones for use as ornaments and in games, and used powdered sea otter baculum
as a medicine for fever.
Among the Ainu, the otter is portrayed as an occasional messenger between humans and the creator. The sea otter is a recurring figure in Ainu folklore. A major Ainu epic
, the Kutune Shirka
, tells the tale of wars and struggles over a golden sea otter. Versions of a widespread Aleut legend tell of lovers or despairing women who plunge into the sea and become otters. These links have been associated with the many human-like behavioral features of the sea otter, including apparent playfulness, strong mother-pup bonds and tool use, yielding to ready anthropomorphism
. The beginning of commercial exploitation had a great impact on the human as well as animal populations – the Ainu and Aleuts have been displaced or their numbers are dwindling, while the coastal tribes of North America, where the otter is in any case greatly depleted, no longer rely as intimately on sea mammals for survival.
Since the mid-1970s, the beauty and charisma of the species have gained wide appreciation, and the sea otter has become an icon of environmental conservation. The round, expressive face and soft furry body of the sea otter are depicted in a wide variety of souvenirs, postcards, clothing, and stuffed toys.
, and are featured in over 40 public aquarium
s and zoo
s. The Seattle Aquarium
became the first institution to raise sea otters from conception to adulthood with the birth of Tichuk in 1979, followed by three more pups in the early 1980s. In 2007, a YouTube
video of two sea otters holding paws drew 1.5 million viewers in two weeks, and currently has over 15 million views. Filmed five years previously at the Vancouver Aquarium
, it was YouTube's most popular animal video at the time, although it has since been surpassed. The lighter-colored otter in the video is Nyac, a survivor of the 1989 Exxon Valdez oil spill
. Nyac died in September 2008, at the age of 20.
Marine mammal
Marine mammals, which include seals, whales, dolphins, and walruses, form a diverse group of 128 species that rely on the ocean for their existence. They do not represent a distinct biological grouping, but rather are unified by their reliance on the marine environment for feeding. The level of...
native to the coasts of the northern and eastern North Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. Adult sea otters typically weigh between 14 and 45 kg
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...
(30 to 100 lb
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...
), making them the heaviest members of the weasel family
Mustelidae
Mustelidae , commonly referred to as the weasel family, are a family of carnivorous mammals. Mustelids are diverse and the largest family in the order Carnivora, at least partly because in the past it has been a catch-all category for many early or poorly differentiated taxa...
, but among the smallest marine mammals. Unlike most marine mammals, the sea otter's primary form of insulation is an exceptionally thick coat of fur
Fur
Fur is a synonym for hair, used more in reference to non-human animals, usually mammals; particularly those with extensives body hair coverage. The term is sometimes used to refer to the body hair of an animal as a complete coat, also known as the "pelage". Fur is also used to refer to animal...
, the densest in the animal kingdom. Although it can walk on land, the sea otter lives mostly in the ocean.
The sea otter inhabits offshore environments where it dives to the sea floor to forage
Forage
Forage is plant material eaten by grazing livestock.Historically the term forage has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used more loosely to include similar plants cut for fodder and carried to the animals, especially...
. It preys mostly upon marine invertebrates such as sea urchin
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...
s, various molluscs and crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, and some species of fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate 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...
. Its foraging and eating habits are noteworthy in several respects. First, its use of rocks to dislodge prey and to open shells makes it one of the few mammal species to use tools. In most of its range, it is a keystone species
Keystone species
A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. Such species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and...
, controlling sea urchin populations which would otherwise inflict extensive damage to kelp forest
Kelp forest
Kelp forests are underwater areas with a high density of kelp. They are recognized as one of the most productive and dynamic ecosystems on Earth. Smaller areas of anchored kelp are called kelp beds....
ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
s. Its diet includes prey species that are also valued by humans as food, leading to conflicts between sea otters and fisheries.
Sea otters, whose numbers were once estimated at 150,000–300,000, were hunted extensively for their fur between 1741 and 1911, and the world population fell to 1,000–2,000 individuals in a fraction of their historic range. A subsequent international ban on hunting, conservation efforts, and reintroduction programs into previously populated areas have contributed to numbers rebounding, and the species now occupies about two-thirds of its former range. The recovery of the sea otter is considered an important success in marine conservation
Marine conservation
Marine conservation, also known as marine resources conservation, is the protection and preservation of ecosystems in oceans and seas. Marine conservation focuses on limiting human-caused damage to marine ecosystems, and on restoring damaged marine ecosystems...
, although populations in the Aleutian Islands and 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...
have recently declined or have plateaued at depressed levels. For these reasons (as well as its particular vulnerability to oil spill
Oil spill
An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters...
s) the sea otter remains classified as an endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
.
Taxonomy
The first scientific description of the sea otter is contained in the field notes of Georg Steller from 1751, and the species was described by Linnaeus in his Systema NaturaeSystema Naturae
The book was one of the major works of the Swedish botanist, zoologist and physician Carolus Linnaeus. The first edition was published in 1735...
of 1758. Originally named Lutra marina, it underwent numerous name changes before being accepted as Enhydra lutris in 1922. The generic name Enhydra, derives from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
en/εν "in" and hydra/ύδρα "water", meaning "in the water", and the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
word lutris, meaning "otter". It was formerly sometimes referred to as the "sea beaver", although it is only distantly related to beaver
Beaver
The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...
s. It is not to be confused with the marine otter
Marine Otter
The marine otter, Lontra felina, is a rare and poorly-known South American mammal of the weasel family . The scientific name means "otter cat", and in Spanish the marine otter is also often referred to as : "marine cat"...
, a rare otter species native to the southern west coast of South America. A number of other otter species, while predominantly living in fresh water, are commonly found in marine coastal habitats. The extinct sea mink
Sea Mink
The Sea Mink, Neovison macrodon, is an extinct North American member of the family Mustelidae. It is the only mustelid, and one of only two terrestrial mammal species in the order Carnivora, to become extinct in historic times . The body of the sea mink was significantly longer than that of the...
of northeast North America is another mustelid that adapted to a marine environment.
Evolution
Mustelidae
Mustelidae , commonly referred to as the weasel family, are a family of carnivorous mammals. Mustelids are diverse and the largest family in the order Carnivora, at least partly because in the past it has been a catch-all category for many early or poorly differentiated taxa...
, a diverse group that includes the thirteen otter
Otter
The Otters are twelve species of semi-aquatic mammals which feed on fish and shellfish, and also other invertebrates, amphibians, birds and small mammals....
species and terrestrial animals such as weasel
Weasel
Weasels are mammals forming the genus Mustela of the Mustelidae family. They are small, active predators, long and slender with short legs....
s, badger
Badger
Badgers are short-legged omnivores in the weasel family, Mustelidae. There are nine species of badger, in three subfamilies : Melinae , Mellivorinae , and Taxideinae...
s, and mink
Mink
There are two living species referred to as "mink": the European Mink and the American Mink. The extinct Sea Mink is related to the American Mink, but was much larger. All three species are dark-colored, semi-aquatic, carnivorous mammals of the family Mustelidae, which also includes the weasels and...
s. It is unique among the mustelids in not making dens or burrow
Burrow
A burrow is a hole or tunnel dug into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion. Burrows provide a form of shelter against predation and exposure to the elements, so the burrowing way of life is quite popular among the...
s, in having no functional anal scent glands, and in being able to live its entire life without leaving the water. The only member of the genus Enhydra, the sea otter is so different from other mustelid species that as recently as 1982, some scientists believed it was more closely related to the earless seal
Earless seal
The true seals or earless seals are one of the three main groups of mammals within the seal superfamily, Pinnipedia. All true seals are members of the family Phocidae . They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae...
s. Genetic
Molecular phylogeny
Molecular phylogenetics is the analysis of hereditary molecular differences, mainly in DNA sequences, to gain information on an organism's evolutionary relationships. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree...
analysis indicates that the sea otter and its closest extant relatives, which include the African speckle-throated otter
Speckle-throated Otter
The spotted-necked otter , or speckle-throated otter, is an otter native to sub-Saharan Africa. It is a smallish otter 95-105 cm long, including the tail, and weighing 3 to 6.5 kg . Like other otters it is sleek and has webbed paws for swimming...
, Eurasian otter, African clawless otter
African Clawless Otter
The African clawless otter , also known as the cape clawless otter or groot otter, is the second largest freshwater species of otter. African clawless otters are found near permanent bodies of water in savannah and lowland forest areas...
and oriental small-clawed otter
Oriental Small-clawed Otter
The oriental small-clawed otter , also known as Asian small-clawed otter, is the smallest otter species in the world, weighing less than 5 kg. It lives in mangrove swamps and freshwater wetlands of Bangladesh, Burma, India, southern China, Taiwan, Laos, Malaysia, Indonesia, the Philippines,...
, shared an ancestor approximately 5 million years ago (mya).
Fossil evidence indicates that the Enhydra lineage became isolated in the North Pacific approximately 2 mya, giving rise to the now-extinct Enhydra macrodonta and the modern sea otter, Enhydra lutris. The sea otter evolved initially in northern 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...
and Russia, and then spread east to the Aleutian Islands, mainland 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...
, and down the North American coast. In comparison to cetacea
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...
ns, sirenians, and pinniped
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
s, which entered the water approximately 50 mya, 40 mya, and 20 mya, respectively, the sea otter is a relative newcomer to a marine existence. In some respects, however, the sea otter is more fully aquatically adapted than pinnipeds, which must haul out on land or ice to give birth.
Subspecies
There are three recognized subspecies, which vary in body size and in some skull and dental characteristics:| Subspecies | Trinomial authority | Common names | Description | Range | Synonyms |
|---|---|---|---|---|---|
| E. l. lutris (Nominate subspecies) |
Linnaeus, 1758 | Common sea otter Asian sea otter Commander sea otter Kuril sea otter |
The largest subspecies, with a wide skull and short nasal bones | 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... to the Commander Islands in the western Pacific Ocean |
gracilis (Bechstein, 1800) kamtschatica (Dybowski, 1922) marina (Erxleben, 1777) orientalis (Oken, 1816) stelleri (Lesson, 1827) |
| E. l. nereis |
Merriam, 1904 | Southern sea otter Californian sea otter |
Has a narrower skull with a long rostrum Rostrum (anatomy) The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes.... and small teeth |
Coast of 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... |
|
E. l. kenyoni |
Wilson, 1991 | Northern sea otter | Alaska and the Pacific west coast from the Aleutian islands to British Columbia, Washington, and northern Oregon. After being extirpated from southern British Columbia due to overhunting, it has since been re-introduced off Vancouver Island Vancouver Island Vancouver Island is a large island in British Columbia, Canada. It is one of several North American locations named after George Vancouver, the British Royal Navy officer who explored the Pacific Northwest coast of North America between 1791 and 1794... and the Olympic Peninsula Olympic Peninsula The Olympic Peninsula is the large arm of land in western Washington state of the USA, that lies across Puget Sound from Seattle. It is bounded on the west by the Pacific Ocean, the north by the Strait of Juan de Fuca, and the east by Puget Sound. Cape Alava, the westernmost point in the contiguous... |
||
The reintroduction effort off the Oregon coast was not successful. However, reintroductions in 1969 and 1970 off the Washington coast were very successful and sea otters have been expanding their range since. They have now entered the Strait of Juan de Fuca
Strait of Juan de Fuca
The Strait of Juan de Fuca is a large body of water about long that is the Salish Sea outlet to the Pacific Ocean...
and can be found almost as far east as Pillar Point. Individuals have even been seen in the San Juan Islands and northern Puget Sound.
Physical characteristics
Marine mammal
Marine mammals, which include seals, whales, dolphins, and walruses, form a diverse group of 128 species that rely on the ocean for their existence. They do not represent a distinct biological grouping, but rather are unified by their reliance on the marine environment for feeding. The level of...
species but is the heaviest mustelid. Male sea otters usually 22 to 45 kg (49 to 99 lb) and are 1.2 to 1.5 m
M
M is the thirteenth letter of the basic modern Latin alphabet.-History:The letter M is derived from the Phoenician Mem, via the Greek Mu . Semitic Mem probably originally pictured water...
(4 to 5 ft) in length, though specimens to 54 kg (119 lb) have been recorded. Females are smaller, weighing 14 to 33 kg (30 to 73 lb) and measuring 1.0 to 1.4 m (3 ft 3 in to 4 ft 7 in) in length. Its baculum
Baculum
The baculum is a bone found in the penis of most mammals. It is absent in humans, but present in other primates, such as the gorilla and chimpanzee.The bone aids in sexual intercourse.-Purpose:...
is, for the male otter's size, very large, massive and bent upwards, measuring 150 mm (6 in) in length and 15 mm wide (0.6 in) at the base.
Unlike other marine mammals, the sea otter has no blubber
Blubber
Blubber is a thick layer of vascularized adipose tissue found under the skin of all cetaceans, pinnipeds and sirenians.-Description:Lipid-rich, collagen fiber–laced blubber comprises the hypodermis and covers the whole body, except for parts of the appendages, strongly attached to the musculature...
and relies on its exceptionally thick fur to keep warm. With up to 150,000 strands of hair per square centimeter (nearly one million per sq in), its fur
Fur
Fur is a synonym for hair, used more in reference to non-human animals, usually mammals; particularly those with extensives body hair coverage. The term is sometimes used to refer to the body hair of an animal as a complete coat, also known as the "pelage". Fur is also used to refer to animal...
is the most dense of any animal. The fur consists of long waterproof guard hairs and short underfur; the guard hairs keep the dense underfur layer dry. Cold water is thus kept completely away from the skin and heat loss is limited. The fur is thick year-round, as it is shed and replaced gradually rather than in a distinct molting season. As the ability of the guard hairs to repel water depends on utmost cleanliness, the sea otter has the ability to reach and groom the fur on any part of its body, taking advantage of its loose skin and an unusually supple skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
. The coloration of the pelage is usually deep brown with silver-gray speckles, but it can range from yellowish or grayish brown to almost black. In adults, the head, throat, and chest are lighter in color than the rest of the body.
The sea otter displays numerous adaptations to its marine environment. The nostrils and small ears can close. The hind feet, which provide most of its propulsion in swimming, are long, broadly flattened, and fully webbed. The fifth digit on each hind foot is longest, facilitating swimming while on its back, but making walking difficult. The tail is fairly short, thick, slightly flattened, and muscular. The front paws are short with retractable claws, with tough pads on the palms that enable gripping slippery prey.
The sea otter propels itself underwater by moving the rear end of its body, including its tail and hind feet, up and down, and is capable of speeds of up to 9 km/h (5.6 mph). When underwater, its body is long and streamlined, with the short forelimbs pressed closely against the chest. When at the surface, it usually floats on its back and moves by sculling its feet and tail from side to side. At rest, all four limbs can be folded onto the torso to conserve heat, whereas on particularly hot days the hind feet may be held underwater for cooling. The sea otter's body is highly buoyant because of its large lung capacity – about 2.5 times greater than that of similar-sized land mammals – and the air trapped in its fur. The sea otter walks with a clumsy rolling gait on land, and can run in a bounding motion.
Long, highly sensitive whiskers and front paws help the sea otter find prey by touch when waters are dark or murky. Researchers have noted that when they approach in plain view, sea otters react more rapidly when the wind is blowing towards the animals, indicating that the sense of smell
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
is more important than sight
Visual perception
Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...
as a warning sense. Other observations indicate that the sea otter's sense of sight is useful above and below the water, although not as good as that of seals. Its hearing
Hearing (sense)
Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...
is neither particularly acute nor poor.
An adult's 32 teeth, particularly the molars
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
, are flattened and rounded, designed to crush rather than cut food. Seals
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
and sea otters are the only carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
s with two pairs of lower incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
teeth rather than three; the adult dental formula
Dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...
is
The sea otter has a metabolic rate two or three times that of comparatively sized terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
mammals. It must eat an estimated 25 to 38% of its own body weight in food each day in order to burn the calories necessary to counteract the loss of heat due to the cold water environment. Its digestive efficiency is estimated at 80 to 85%, and food is digested and passed in as little as three hours. Most of its need for water is met through food, although, in contrast to most other marine mammals, it also drinks seawater. Its relatively large kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
s enable it to derive fresh water from sea water and excrete concentrated urine.
Behavior
The sea otter spends much of its time grooming, which consists of cleaning the fur, untangling knots, removing loose fur, rubbing the fur to squeeze out water and introduce air, and blowing air into the fur. To an observer it appears as if the animal is scratching, however sea otters are not known to have lice or other parasites in the fur. When eating, the sea otter rolls in the water frequently, apparently to wash food scraps from its fur.
Foraging
The sea otter hunts in short dives, often to the sea floor. Although it can hold its breath for up to five minutes, its dives typically last about one minute and no more than four. It is the only marine animal capable of lifting and turning over boulders, which it often does with its front paws when searching for prey. The sea otter may also pluck snailSnail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s and other organisms from kelp and dig deep into underwater mud for clam
Clam
The word "clam" can be applied to freshwater mussels, and other freshwater bivalves, as well as marine bivalves.In the United States, "clam" can be used in several different ways: one, as a general term covering all bivalve molluscs...
s. It is the only marine mammal that catches fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate 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...
with its forepaws rather than with its teeth.
Under each foreleg, the sea otter has a loose pouch of skin that extends across the chest. In this pouch (preferentially the left one), the animal stores collected food to bring to the surface. In this pouch they also keep a rock unique to each otter that is used to break open shellfish and clams. There, the sea otter eats while floating on its back, using its forepaws to tear food apart and bring it to its mouth. It can chew and swallow small mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
s with their shells, whereas large mussel shells may be twisted apart. It uses its lower incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
teeth to access the meat in shellfish.
To eat large sea urchins, which are mostly covered with spines, the sea otter bites through the underside where the spines are shortest, and licks the soft contents out of the urchin's shell.
The sea otter's use of rocks when hunting and feeding makes it one of the few mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
species to use tools. To open hard shells, it may pound its prey with both paws against a rock on its chest. To pry an abalone
Abalone
Abalone , from aulón, are small to very large-sized edible sea snails, marine gastropod molluscs in the family Haliotidae and the genus Haliotis...
off its rock, it hammers the abalone shell using a large stone, with observed rates of 45 blows in 15 seconds. Releasing an abalone, which can cling to rock with a force equal to 4,000 times its own body weight, requires multiple dives.
Social structure
Although each adult and independent juvenile forages alone, sea otters tend to rest together in single-sex groups called rafts. A raft typically contains 10 to 100 animals, with male rafts being larger than female ones. The largest raft ever seen contained over 2000 sea otters. To keep from drifting out to sea when resting and eating, sea otters may wrap themselves in kelpKelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....
.
A male sea otter is most likely to mate if he maintains a breeding territory in an area that is also favored by females. As autumn is the peak breeding season in most areas, males typically defend their territory only from spring to autumn. During this time, males patrol the boundaries of their territories to exclude other males, although actual fighting is rare. Adult females move freely between male territories, where they outnumber adult males by an average of five to one. Males who do not have territories tend to congregate in large male-only groups, and swim through female areas when searching for a mate.
The species exhibits a variety of vocal behaviors. The cry of a pup is often compared to that of a seagull. Females coo when they are apparently content; males may grunt instead. Distressed or frightened adults may whistle, hiss, or in extreme circumstances, scream.
Although sea otters can be playful and sociable, they are not considered to be truly social animal
Social animal
A social animal is a loosely defined term for an organism that is highly interactive with other members of its species to the point of having a recognizable and distinct society.All mammals are social to the extent that mothers and offspring bond...
s. They spend much time alone, and each adult can meet its own needs in terms of hunting, grooming, and defense.
Reproduction and lifecycle
Births occur year-round, with peaks between May and June in northern populations and between January and March in southern populations. Gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
appears to vary from four to twelve months, as the species is capable of delayed implantation followed by four months of pregnancy. In California, sea otters usually breed every year, about twice as often as sea otters in Alaska.
Birth usually takes place in the water and typically produces a single pup weighing 1.4 to 2.3 kg (3 to 5 lb). Twins occur in 2% of births; however, usually only one pup survives. At birth, the eyes are open, ten teeth are visible, and the pup has a thick coat of baby fur. Mothers have been observed to lick and fluff a newborn for hours; after grooming, the pup's fur retains so much air that the pup floats like a cork and cannot dive. The fluffy baby fur is replaced by adult fur after about thirteen weeks.
Lactation
Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, however it predates mammals. In humans the process of feeding milk is called breastfeeding or nursing...
lasts six to eight months in Californian populations and four to twelve months in Alaska, with the mother beginning to offer bits of prey at one to two months. The milk from a sea otter's two abdominal nipple
Nipple
In its most general form, a nipple is a structure from which a fluid emanates. More specifically, it is the projection on the breasts or udder of a mammal by which breast milk is delivered to a mother's young. In this sense, it is often called a teat, especially when referring to non-humans, and...
s is rich in fat and more similar to the milk of other marine mammals than to that of other mustelids. A pup, with guidance from its mother, practices swimming and diving for several weeks before it is able to reach the sea floor. Initially the objects it retrieves are of little food value, such as brightly colored starfish and pebbles. Juveniles are typically independent at six to eight months, however a mother may be forced to abandon a pup if she cannot find enough food for it and at the other extreme, a pup may nurse until it is almost adult size. Pup mortality is high, particularly during an individual's first winter – by one estimate, only 25% of pups survive their first year. Pups born to experienced mothers have the highest survival rates.
Females perform all tasks of feeding and raising offspring, and have occasionally been observed caring for orphaned pups. Much has been written about the level of devotion of sea otter mothers for their pups – a mother gives her infant almost constant attention, cradling it on her chest away from the cold water and attentively grooming its fur. When foraging, she leaves her pup floating on the water, sometimes wrapped in kelp to keep it from floating away; if the pup is not sleeping, it cries loudly until she returns. Mothers have been known to carry their pup for days after the pup's death.
Females become sexually mature at around three or four years of age and males at around five; however, males often do not successfully breed until a few years later. A captive male sired offspring at age 19. In the wild, sea otters live to a maximum age of 23 years, with average lifespans of 10–15 years for males and 15–20 years for females. Several captive individuals have lived past 20 years, and a female at the Seattle Aquarium
Seattle Aquarium
The Seattle Aquarium is a public aquarium opened in 1977 and located on Pier 59 on the Elliott Bay waterfront in Seattle, Washington, USA. It is accredited by the Association of Zoos and Aquariums .-History:...
died at the age of 28 years. Sea otters in the wild often develop worn teeth, which may account for their apparently shorter lifespans.
Population and distribution
Kelp forest
Kelp forests are underwater areas with a high density of kelp. They are recognized as one of the most productive and dynamic ecosystems on Earth. Smaller areas of anchored kelp are called kelp beds....
s, and barrier reefs. Although they are most strongly associated with rocky substrates
Substrate (marine biology)
Stream substrate is the material that rests at the bottom of a stream. There are several classification guides. One is:*Mud – silt and clay.*Sand – Particles between 0.06 and 2 mm in diameter.*Granule – Between 2 and 4 mm in diameter....
, sea otters can also live in areas where the sea floor consists primarily of mud, sand, or silt. Their northern range is limited by ice, as sea otters can survive amidst drift ice
Drift ice
Drift ice is ice that floats on the surface of the water in cold regions, as opposed to fast ice, which is attached to a shore. Usually drift ice is carried along by winds and sea currents, hence its name, "drift ice"....
but not land-fast ice. Individuals generally occupy a home range a few kilometers long, and remain there year-round.
The sea otter population is thought to have once been 150,000 to 300,000, stretching in an arc across the North Pacific from northern Japan to the central Baja California Peninsula
Baja California Peninsula
The Baja California peninsula , is a peninsula in northwestern Mexico. Its land mass separates the Pacific Ocean from the Gulf of California. The Peninsula extends from Mexicali, Baja California in the north to Cabo San Lucas, Baja California Sur in the south.The total area of the Baja California...
in Mexico. The fur trade that began in the 1740s reduced the sea otter's numbers to an estimated 1,000 to 2,000 members in thirteen colonies. In about two-thirds of its former range, the species is at varying levels of recovery, with high population densities in some areas and threatened
Threatened species
Threatened species are any speciesg animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future.The World Conservation Union is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories,...
populations in others. Sea otters currently have stable populations in parts of the Russian east coast, Alaska, British Columbia, Washington, and California, and there have been reports of recolonizations in Mexico and Japan. Population estimates made between 2004 and 2007 give a worldwide total of approximately 107,000 sea otters.
Russia
Currently, the most stable and secure part of the sea otter's range is RussiaRussia
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...
. Before the 19th century there were around 20,000 to 25,000 sea otters in 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...
, with more on Kamchatka and the Commander Islands. After the years of the Great Hunt, the population in these areas, currently part of Russia, was only 750. As of 2004, sea otters have repopulated all of their former habitat in these areas, with an estimated total population of about 27,000. Of these, about 19,000 are in the Kurils, 2000 to 3500 on Kamchatka and another 5000 to 5500 on the Commander Islands. Growth has slowed slightly, suggesting that the numbers are reaching carrying capacity
Carrying capacity
The carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment...
.
Alaska
AlaskaAlaska
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...
is the heartland of the sea otter's range. In 1973, the sea otter population in Alaska was estimated at between 100,000 and 125,000 animals. By 2006, however, the Alaska population had fallen to an estimated 73,000 animals. A massive decline in sea otter populations in the Aleutian Islands accounts for most of the change; the cause of this decline is not known, although 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...
predation is suspected. The sea otter population in Prince William Sound
Prince William Sound
Prince William Sound is a sound off the Gulf of Alaska on the south coast of the U.S. state of Alaska. It is located on the east side of the Kenai Peninsula. Its largest port is Valdez, at the southern terminus of the Trans-Alaska Pipeline System...
was also hit hard by the Exxon Valdez oil spill
Exxon Valdez oil spill
The Exxon Valdez oil spill occurred in Prince William Sound, Alaska, on March 24, 1989, when the Exxon Valdez, an oil tanker bound for Long Beach, California, struck Prince William Sound's Bligh Reef and spilled of crude oil. It is considered to be one of the most devastating human-caused...
, which killed thousands of sea otters in 1989.
British Columbia and Washington
Along the North American coast south of Alaska, the sea otter's range is discontinuous. Although a remnant population of sea otter survived off Vancouver Island into the twentieth century, it died out despite the 1911 international protection treaty, with the last sea otter taken near KyuquotKyuquot, British Columbia
Kyuquot is an unincorporated settlement and First Nations Indian reserve community located on Kyuquot Sound on northwestern Vancouver Island, British Columbia, Canada. Meaning people of Kayukw in the Nuu-chah-nulth language, it is partly the community of the Kyuquot and Cheklesahht peoples, whose...
in 1929. From 1969 to 1972, 89 sea otters were flown or shipped from Alaska to the west coast of Vancouver Island. This population expanded to over 3,000 as of 2004, and their range on the island's west coast expanded from Cape Scott
Cape Scott Provincial Park
Cape Scott Provincial Park is a provincial park located at the cape of the same name, which is the northwestern tip of Vancouver Island, British Columbia, Canada. First established in 1973 with c. of area, later boundary revisions form an area of 22,290 ha...
in the north to Barkley Sound
Barkley Sound
Barkley Sound, also known historically as Barclay Sound, is south of Ucluelet and north of Bamfield on the west coast of Vancouver Island and forms the entrance to the Alberni Inlet...
to the south. In 1989, a separate colony was discovered in the central British Columbia coast. It is not known if this colony, which had a size of about 300 animals in 2004, was founded by transplanted otters or by survivors of the fur trade.
In 1969 and 1970, 59 sea otters were translocated from Amchitka Island to Washington. Annual surveys between 2000 and 2004 have recorded between 504 and 743 individuals, and their range is in the Olympic Peninsula
Olympic Peninsula
The Olympic Peninsula is the large arm of land in western Washington state of the USA, that lies across Puget Sound from Seattle. It is bounded on the west by the Pacific Ocean, the north by the Strait of Juan de Fuca, and the east by Puget Sound. Cape Alava, the westernmost point in the contiguous...
from just south of Destruction Island to Pillar Point.
San Juan Islands
The San Juan Islands are an archipelago in the northwest corner of the contiguous United States between the US mainland and Vancouver Island, British Columbia, Canada. The San Juan Islands are part of the U.S...
and Puget Sound
Puget Sound
Puget Sound is a sound in the U.S. state of Washington. It is a complex estuarine system of interconnected marine waterways and basins, with one major and one minor connection to the Strait of Juan de Fuca and the Pacific Ocean — Admiralty Inlet being the major connection and...
almost always turn out to be northern river otter
Northern River Otter
The North American river otter , also known as the northern river otter or the common otter, is a semiaquatic mammal endemic to the North American continent, found in and along its waterways and coasts. An adult river otter can weigh between 5 and 14 kg...
s which are commonly seen along the seashore. However, biologists have confirmed isolated sightings of sea otters in these areas since the mid-1990s.
California
The spring 2007 sea otter survey counted 3,026 sea otters in the central Californian coast, down from an estimated pre-fur trade population of 16,000. California's sea otters are the descendants of a single colony of about 50 southern sea otters discovered near Big SurBig Sur
Big Sur is a sparsely populated region of the Central Coast of California where the Santa Lucia Mountains rise abruptly from the Pacific Ocean. The name "Big Sur" is derived from the original Spanish-language "el sur grande", meaning "the big south", or from "el país grande del sur", "the big...
in 1938; their principal range is now from just south of San Francisco to Santa Barbara County. In the late 1980s, the U.S. Fish and Wildlife Service relocated about 140 Californian sea otters to San Nicolas Island
San Nicolas Island
San Nicolas Island is the most remote of California's Channel Islands. It is part of Ventura County. The 14,562 acre island is currently controlled by the United States Navy and is used as a weapons testing and training facility, served by Naval Outlying Field San Nicolas Island...
in southern California, in the hope of establishing a reserve population should the mainland be struck by an oil spill. To the surprise of biologists, the San Nicholas population initially shrank as the animals migrated back to the mainland. As of 2005, only 30 sea otters remained at San Nicholas, thriving on the abundant prey around the island. The plan that authorized the translocation program had predicted that carrying capacity would be reached within 5 to 10 years.
When the Fish and Wildlife Service implemented the translocation program, it also attempted to implement "zonal management" of the Californian population. To manage the competition between sea otters and fisheries, it declared an "otter-free zone" stretching from Point Conception
Point Conception
Point Conception is a headland along the Pacific coast of U.S. state of California, located in southwestern Santa Barbara County. It is the point where the Santa Barbara Channel meets the Pacific Ocean, and as the corner between the mostly north-south trending portion of coast to the north and the...
to the Mexican border. In this zone, only San Nicolas Island was designated as sea otter habitat, and sea otters found elsewhere in the area were supposed to be captured and relocated. These plans were abandoned after it proved impractical to capture the hundreds of otters which ignored regulations and swam into the zone. However, after engaging in a period of public commentary in 2005, the Fish and Wildlife Service has yet to release a formal decision on the issue.
Sea otters were once numerous in San Francisco Bay
San Francisco Bay
San Francisco Bay is a shallow, productive estuary through which water draining from approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean...
. Historical records reveal that the Russian-American Company
Russian-American Company
The Russian-American Company was a state-sponsored chartered company formed largely on the basis of the so-called Shelekhov-Golikov Company of Grigory Shelekhov and Ivan Larionovich Golikov The Russian-American Company (officially: Under His Imperial Majesty's Highest Protection (patronage)...
snuck Aleuts into San Francisco Bay multiple times, despite the Spanish capturing or shooting them while hunting sea otters in the estuaries of San Jose
San Jose, California
San Jose is the third-largest city in California, the tenth-largest in the U.S., and the county seat of Santa Clara County which is located at the southern end of San Francisco Bay...
, San Mateo
San Mateo, California
San Mateo is a city in San Mateo County, California, United States, in the San Francisco Bay Area. With a population of approximately 100,000 , it is one of the larger suburbs on the San Francisco Peninsula, located between Burlingame to the north, Foster City to the east, Belmont to the south,...
, San Bruno
San Bruno, California
San Bruno is a city in San Mateo County, California, United States. The population was 41,114 at the 2010 census.The city is adjacent to San Francisco International Airport and Golden Gate National Cemetery.-Geography:San Bruno is located at...
and around Angel Island. The founder of Fort Ross, Ivan Kuskov
Ivan Kuskov
Ivan Aleksandrovich Kuskov was the senior assistant to Aleksandr Baranov, the Chief Administrator of the Russian-American Company A native of Totma, Russia, he served in the RAC for 31 years, attaining the rank of Commerce Counselor and being awarded the gold medal "for zealous service" from...
, finding otter scarce on his second voyage to Bodega Bay in 1812, sent a party of Aleuts to San Francisco Bay where they met another Russian party and an American party, and caught 1,160 sea otters in three months. By 1817 sea otters in the area were practically eliminated and the Russians sought permission from the Spanish and the Mexican governments to hunt further and further south of San Francisco. Remnant sea otter populations may have survived in the bay until 1840, when the Rancho Punta de Quentin
Rancho Punta de Quentin
Rancho Punta de Quentin was a Mexican land grant in present day Marin County, California given in 1840 by Governor Juan B. Alvarado to John B.R. Cooper...
was granted to Captain John B. R. Cooper, a sea captain from Boston, by Mexican Governor Juan Bautista Alvarado
Juan Bautista Alvarado
Juan Bautista Valentín Alvarado y Vallejo was a Californio and twice Governor of Alta California from 1836 to 1837, and 1838 to 1842.-Early years:...
along with a license to hunt sea otters, reportedly then prevalent at the mouth of Corte Madera Creek
Corte Madera Creek (Marin County, California)
Corte Madera Creek is a short stream which flows southeast for in Marin County, California. Corte Madera Creek is formed by the confluence of San Anselmo Creek and Ross Creek in Ross and entering a tidal marsh at Kentfield before connecting to San Francisco Bay near Corte Madera.-History:The...
.
Although the southern sea otter's range has continuously expanded from Big Sur since protection in 1911, in the last two years the otter population and its range have contracted. As of spring 2010 the northern boundary has moved from about Tunitas Creek
Tunitas Creek
Tunitas Creek is a stream in San Mateo County, California. Tunitas is Spanish for "Little Prickly Pears". Historically the creek was also known as Arroyo de Las Tunitas....
to a point 2 km southeast of Pigeon Point, and the southern boundary has moved from approximately Coal Oil Point to Gaviota State Park
Gaviota State Park
Gaviota State Park is a California State Park located in southern Santa Barbara County, California, U.S., about 33 miles west of the city of Santa Barbara. It consists of 2,790 acres extending from the Pacific coast to the crest of the Santa Ynez Mountains, and is adjacent to Los Padres National...
. Recently a toxin called microcystin
Microcystin
Microcystins are cyclic nonribosomal peptides produced by cyanobacteria . They are cyanotoxins and can be very toxic for plants and animals including humans. Their hepatotoxicity may cause serious damage to the liver. Microcystins can strongly inhibit protein phosphatases type 1 and 2A , and are...
, produced by a type of cyanobacteria (Microcystis), seems to be concentrated in the shellfish that otters eat, poisoning them. Cyanobacteria are found in stagnant freshwater enriched with nitrogen and phosphorus from septic tank and agricultural fertilizer runoff, and may be flushed into the ocean when streamflows are high in the rainy season. A record number of sea otter carcasses were found on California's coastline in 2010, with increased shark attacks an increasing component of the mortality.
Oregon
The last native sea otter in Oregon was probably shot and killed in 1906. In 1970 and 1971, a total of 95 sea otters were transplanted from Amchitka Island, Alaska to the Southern Oregon coast. However, this translocation effort failed and otters soon again disappeared from the state.In 2004 a lone male sea otter took up residence at Simpson Reef off of Cape Arago for six months. This male is thought to have originated from a colony in Washington, but disappeared after a coastal storm.
The most recent sighting of a sea otter off the Oregon coast took place 18 February 2009, in Depoe Bay, Oregon. The lone male sea otter could have traveled from either California or Washington.
Diet
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...
s, a variety of bivalves such as clam
Clam
The word "clam" can be applied to freshwater mussels, and other freshwater bivalves, as well as marine bivalves.In the United States, "clam" can be used in several different ways: one, as a general term covering all bivalve molluscs...
s and mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
s, abalone
Abalone
Abalone , from aulón, are small to very large-sized edible sea snails, marine gastropod molluscs in the family Haliotidae and the genus Haliotis...
, other mollusks, crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, and snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s. Its prey ranges in size from tiny limpet
Limpet
Limpet is a common name for a number of different kinds of saltwater and freshwater snails ; it is applied to those snails that have a simple shell which is more or less conical in shape, and either is not spirally coiled, or appears not to be coiled in the adult snails.The name limpet is most...
s and crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s to giant octopus
Giant octopus
Enteroctopus is an octopus genus, many of whose members are sometimes known as giant octopuses.- Description :Enteroctopus is a genus of generally temperate octopuses. Members of the genus Enteroctopus are characterized by their large size and are often known as the giant octopuses...
es. Where prey such as sea urchins, clams, and abalone are present in a range of sizes, sea otters tend to select larger items over smaller ones of similar type. In California, it has been noted that sea otters ignore Pismo clam
Pismo clam
Tivela stultorum, also known as the Pismo clam, is a species of saltwater clam in the genus Tivela. It is native to the eastern Pacific Ocean . As the name implies, the Pismo clam lives in Pismo Beach, California....
s smaller than 3 inches (7 cm) across.
In a few northern areas, fish are also eaten. In studies performed at Amchitka Island in the 1960s, where the sea otter population was at carrying capacity
Carrying capacity
The carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment...
, 50% of food found in sea otter stomachs was fish. The fish species were usually bottom-dwelling and sedentary or sluggish forms, such as Hemilepidotus hemilepidotus and family Tetraodontidae. However, south of Alaska on the North American coast, fish are a negligible or extremely minor part of the sea otter's diet. Contrary to popular depictions, sea otters rarely eat starfish, and any kelp
Kelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....
that is consumed apparently passes through the sea otter's system undigested.
The individuals within a particular area often differ in their foraging methods and their prey types, and tend to follow the same patterns as their mothers. The diet of local populations also changes over time, as sea otters can significantly deplete populations of highly preferred prey such as large sea urchins, and prey availability is also affected by other factors such as fishing by humans. Sea otters can thoroughly remove abalone from an area except for specimens in deep rock crevices, however, they never completely wipe out a prey species from an area. A 2007 Californian study demonstrated that in areas where food was relatively scarce, a wider variety of prey was consumed. However, surprisingly, the diets of individuals were more specialized in these areas than in areas where food was plentiful.
As a keystone species
Sea otters are a classic example of a keystone speciesKeystone species
A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. Such species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and...
; their presence affects the ecosystem more profoundly than their size and numbers would suggest. Sea otters keep the population of certain benthic (sea floor) herbivores, particularly sea urchin
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...
s, in check. Sea urchins graze on the lower stems of kelp
Kelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....
, causing the kelp to drift away and die. Loss of the habitat and nutrients provided by kelp forest
Kelp forest
Kelp forests are underwater areas with a high density of kelp. They are recognized as one of the most productive and dynamic ecosystems on Earth. Smaller areas of anchored kelp are called kelp beds....
s leads to profound cascade effects
Cascade effect (ecology)
An ecological cascade effect is a series of secondary extinctions that is triggered by the primary extinction of a key species in an ecosystem. Secondary extinctions are likely to occur when the threatened species are: dependent on a few specific food sources, mutualistic, or forced to coexist...
on the marine ecosystem. North Pacific areas that do not have sea otters often turn into urchin barren
Urchin barren
An urchin barren is an area of the subtidal where the population growth of sea urchins has gone unchecked, causing destructive grazing of kelp beds or kelp forests ....
s, with abundant sea urchins and no kelp forest.
Big Sur
Big Sur is a sparsely populated region of the Central Coast of California where the Santa Lucia Mountains rise abruptly from the Pacific Ocean. The name "Big Sur" is derived from the original Spanish-language "el sur grande", meaning "the big south", or from "el país grande del sur", "the big...
coast of California However, some kelp forest ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
s in California have also thrived without sea otters, with sea urchin populations apparently controlled by other factors. The role of sea otters in maintaining kelp forests has been observed to be more important in areas of open coast than in more protected bays and estuaries.
In addition to promoting growth of kelp forests, sea otters can also have a profound effect in rocky areas that tend to be dominated by mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
beds. They remove mussels from rocks, liberating space for competitive species and thereby increasing the diversity of species in the area.
Predators
Predation of sea otters does occur, although it is not common. Many predators find the otter, with their pungent scent glands, distasteful and young predators may kill an otter and not eat them. Leading mammalian predators of this species include orcaOrca
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 and 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...
s; bald eagle
Bald Eagle
The Bald Eagle is a bird of prey found in North America. It is the national bird and symbol of the United States of America. This sea eagle has two known sub-species and forms a species pair with the White-tailed Eagle...
s also prey on pups by snatching them from the water surface.
On land, young sea otters may face attack from bear
Bear
Bears are mammals of the family Ursidae. Bears are classified as caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although there are only eight living species of bear, they are widespread, appearing in a wide variety of habitats throughout the Northern...
s and coyote
Coyote
The coyote , also known as the American jackal or the prairie wolf, is a species of canine found throughout North and Central America, ranging from Panama in the south, north through Mexico, the United States and Canada...
s. In California, bites from shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
s, particularly great white shark
Great white shark
The great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...
s, have been estimated to cause 10% of sea otter deaths and are one of the reasons the population has not expanded further north. It is believed that the great white shark
Great white shark
The great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...
is their primary predator and dead sea otters have been found with injuries from shark bites, although there is no evidence that sharks actually eat them.
An exhibit at the San Diego Natural History Museum
San Diego Natural History Museum
The San Diego Natural History Museum was founded in 1874 as the San Diego Society of Natural History. The present location of the museum in San Diego's Balboa Park was dedicated on January 14, 1933....
states that cat feces from urban runoff carries parasites to the ocean and kills sea otters.
Fur trade
Archaeological evidence indicates that for thousands of years, indigenous peoples
Indigenous peoples
Indigenous peoples are ethnic groups that are defined as indigenous according to one of the various definitions of the term, there is no universally accepted definition but most of which carry connotations of being the "original inhabitants" of a territory....
have hunted sea otters for food and fur. Large-scale hunting, part of the Maritime Fur Trade
Maritime Fur Trade
The Maritime Fur Trade was a ship-based fur trade system that focused on acquiring furs of sea otters and other animals from the indigenous peoples of the Pacific Northwest Coast and natives of Alaska. The furs were mostly sold in China in exchange for tea, silks, porcelain, and other Chinese...
, which would eventually kill approximately one million sea otters, began in the 18th century when hunters and traders began to arrive from all over the world to meet foreign demand for otter pelts, which were one of the world's most valuable types of fur.
In the early 18th century, Russians began to hunt sea otters in 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 sold them to China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. Russia was also exploring the far northern Pacific at this time, and sent Vitus Bering
Vitus Bering
Vitus Jonassen Bering Vitus Jonassen Bering Vitus Jonassen Bering (also, less correNavy]], a captain-komandor known among the Russian sailors as Ivan Ivanovich. He is noted for being the first European to discover Alaska and its Aleutian Islands...
to map the Arctic coast and find routes from Siberia to North America. In 1741, on his second North Pacific voyage, Bering was shipwrecked off Bering Island
Bering Island
Bering Island is located off the Kamchatka Peninsula in the Bering Sea. At long by wide, it is the largest of the Commander Islands with the area of ....
in the Commander Islands, where Bering and many of his crew died. The surviving crew members, which included naturalist Georg Steller, discovered sea otters on the beaches of the island and spent the winter hunting sea otters and gambling with otter pelts. They returned to Siberia having killed nearly 1000 sea otters, and were able to command high prices for the pelts. Thus began what is sometimes called the "Great Hunt", which would continue for another hundred years.
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...
. In 1799, Emperor Paul I consolidated the rival fur hunting companies into the Russian-American Company
Russian-American Company
The Russian-American Company was a state-sponsored chartered company formed largely on the basis of the so-called Shelekhov-Golikov Company of Grigory Shelekhov and Ivan Larionovich Golikov The Russian-American Company (officially: Under His Imperial Majesty's Highest Protection (patronage)...
, granting it an Imperial charter and protection, and a monopoly over trade rights and territorial acquisition.
Under Aleksandr I the administration of the merchant-controlled Company was transferred to the Imperial Navy, largely due to the alarming reports by naval officers of native abuse, and in 1818 the indigenous peoples of Alaska were granted civil rights equivalent to a townsman status in the Russian Empire.
Other nations joined in the hunt in the south. Along the coasts of what is now Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
and 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...
, Spanish
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
explorers bought sea otter pelts from Native Americans
Indigenous peoples of the Americas
The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America, their descendants and other ethnic groups who are identified with those peoples. Indigenous peoples are known in Canada as Aboriginal peoples, and in the United States as Native Americans...
and sold them in Asia. In 1778, British explorer Captain James Cook reached Vancouver Island
Vancouver Island
Vancouver Island is a large island in British Columbia, Canada. It is one of several North American locations named after George Vancouver, the British Royal Navy officer who explored the Pacific Northwest coast of North America between 1791 and 1794...
and bought sea otter furs from the First Nations people. When Cook's ship later stopped at a Chinese
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
port, the pelts rapidly sold at high prices, and were soon known as "soft gold". As word spread, people from all over Europe and North America began to arrive in the Pacific Northwest
Pacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...
to trade for sea otter furs.
Russian hunting expanded to the south, initiated by American ship captains, who sub-contracted Russian supervisors and Aleut hunters in what is now Washington, Oregon, and California. Between 1803 and 1846, 72 American ships were involved in the otter hunt in California, harvesting an estimated 40,000 skins and tails, compared to only 13 ships of the Russian-American Company, which reported 5,696 otter skins taken between 1806-1846. In 1812 the Russians founded an agricultural settlement at what is now Fort Ross
Fort Ross, California
Fort Ross is a former Russian establishment on the Pacific Coast in what is now Sonoma County, California, in the United States. It was the hub of the southernmost Russian settlements in North America in between 1812 to 1841...
in northern California as their southern headquarters.
Eventually, sea otter populations became so depleted that commercial hunting was no longer viable. In the Aleutian Islands, commercial hunting had stopped by 1808, as a conservation measure imposed by the Russian-American Company. Further restrictions were ordered by the Company in 1834. When Russia sold Alaska
Alaska purchase
The Alaska Purchase was the acquisition of the Alaska territory by the United States from Russia in 1867 by a treaty ratified by the Senate. The purchase, made at the initiative of United States Secretary of State William H. Seward, gained of new United States territory...
to the United States in 1867, the Alaska population had recovered to over 100,000, but Americans resumed hunting and quickly extirpated the sea otter again. Prices rose as the species became rare: During the 1880s, a pelt brought $105 to $165 in the London market, however by 1903 a pelt could be worth as much as $1,125. In 1911, Russia, Japan, Great Britain (for Canada) and the United States signed the Treaty for the Preservation and Protection of Fur Seals
North Pacific Fur Seal Convention of 1911
The North Pacific Fur Seal Convention of 1911, formally known as the Convention between the United States and Other Powers Providing for the Preservation and Protection of Fur Seals, was an international treaty signed on July 7, 1911 designed to manage the commercial harvest of fur bearing mammals ...
, imposing a moratorium on the harvesting of sea otters. So few remained, perhaps only 1,000–2,000 individuals in the wild, that many believed the species would become extinct
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
.
Recovery and conservation
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
, and describes the significant threats to sea otters as oil pollution, 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, poaching
Poaching
Poaching is the illegal taking of wild plants or animals contrary to local and international conservation and wildlife management laws. Violations of hunting laws and regulations are normally punishable by law and, collectively, such violations are known as poaching.It may be illegal and in...
, and conflicts with fisheries – sea otters can drown if entangled in fishing gear. The hunting of sea otters is no longer legal except for limited harvests by indigenous peoples
Indigenous peoples
Indigenous peoples are ethnic groups that are defined as indigenous according to one of the various definitions of the term, there is no universally accepted definition but most of which carry connotations of being the "original inhabitants" of a territory....
in the United States. Poaching was a serious concern in the Russian Far East immediately after the collapse of the Soviet Union in 1991, however it has declined significantly with stricter law enforcement and better economic conditions.
The most significant threat to sea otters is oil spill
Oil spill
An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters...
s. Sea otters are particularly vulnerable, as they rely on their fur to keep warm. When their fur is soaked with oil, it loses its ability to retain air, and the animal quickly dies from hypothermia
Hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...
. The liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
, kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
s, and lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s of sea otters also become damaged after they inhale oil or ingest it when grooming. The Exxon Valdez oil spill
Exxon Valdez oil spill
The Exxon Valdez oil spill occurred in Prince William Sound, Alaska, on March 24, 1989, when the Exxon Valdez, an oil tanker bound for Long Beach, California, struck Prince William Sound's Bligh Reef and spilled of crude oil. It is considered to be one of the most devastating human-caused...
of 24 March 1989 killed thousands of sea otters in Prince William Sound
Prince William Sound
Prince William Sound is a sound off the Gulf of Alaska on the south coast of the U.S. state of Alaska. It is located on the east side of the Kenai Peninsula. Its largest port is Valdez, at the southern terminus of the Trans-Alaska Pipeline System...
, and as of 2006 the lingering oil in the area continues to affect the population. Describing the public sympathy for sea otters that developed from media coverage of the event, a U.S. Fish and Wildlife Service spokesperson wrote:
The small geographic ranges of the sea otter populations in California, Washington, and British Columbia mean that a single major spill could be catastrophic for that state or province. Prevention of oil spills and preparation for the rescue of otters in the event of one are major areas of focus for conservation efforts. Increasing the size and the range of sea otter populations would also reduce the risk of an oil spill wiping out a population. However, because of the species' reputation for depleting shellfish resources, advocates for commercial, recreational, and subsistence shellfish harvesting have often opposed allowing the sea otter's range to increase, and there have even been instances of fishermen and others illegally killing them.
Another area of concern is California, where recovery began to fluctuate or decline in the late 1990s. Unusually high mortality rates amongst adult and sub-adult otters, particularly females, have been reported. Necropsies of dead sea otters indicate that diseases, particularly Toxoplasma gondii
Toxoplasma gondii
Toxoplasma gondii is a species of parasitic protozoa in the genus Toxoplasma. The definitive host of T. gondii is the cat, but the parasite can be carried by many warm-blooded animals . Toxoplasmosis, the disease of which T...
infection and acanthocephala
Acanthocephala
Acanthocephala is a phylum of parasitic worms known as acanthocephales, thorny-headed worms, or spiny-headed worms, characterized by the presence of an evertable proboscis, armed with spines, which it uses to pierce and hold the gut wall of its host...
n parasite infection, are a major cause of sea otter mortality in California. The Toxoplasma gondii parasite, which is often fatal to sea otters, is carried by wild and domestic cats and by opossums, and may be transmitted by domestic cat droppings flushed into the ocean via the sewage system. Although it is clear that disease has contributed to the deaths of many of California's sea otters, it is not known why the Californian population is apparently more affected by disease than populations in other areas.
Sea otter habitat is preserved through several protected areas
Marine Protected Area
Marine Protected Areas, like any protected area, are regions in which human activity has been placed under some restrictions in the interest of conserving the natural environment, it's surrounding waters and the occupant ecosystems, and any cultural or historical resources that may require...
in the United States
Protected areas of the United States
The protected areas of the United States are managed by an array of different federal, state, tribal and local level authorities and receive widely varying levels of protection. Some areas are managed as wilderness, while others are operated with acceptable commercial exploitation. , according to...
, Russia
Protected areas in Russia
The status of the protected areas in Russia is governed by the corresponding law of the Russian FederationThe law establishes the following categories of protected areas:...
and Canada
Protected areas of Canada
Protected areas of Canada have been created to protect ecological integrity, as well as to provide areas for recreation and education. Most of the protected areas in Canada are terrestrial; however, there has been a growing focus to also protect coastal areas, such as the Bowie Seamount. ...
. In marine protected areas, polluting activities such as dumping of waste and oil drilling are typically prohibited. There are estimated to be more than 1,200 sea otters within the Monterey Bay National Marine Sanctuary
Monterey Bay National Marine Sanctuary
The Monterey Bay National Marine Sanctuary is a US Federally protected marine area offshore of California's central coast around Monterey Bay....
, and more than 500 within the Olympic Coast National Marine Sanctuary
Olympic Coast National Marine Sanctuary
The Olympic Coast National Marine Sanctuary is one of 14 marine sanctuaries administered by the National Oceanic and Atmospheric Administration , an agency of the U.S. Department of Commerce. It is located along the Olympic Peninsula of Washington state...
.
Economic impact
Some of the sea otter's preferred prey species, particularly abaloneAbalone
Abalone , from aulón, are small to very large-sized edible sea snails, marine gastropod molluscs in the family Haliotidae and the genus Haliotis...
, clam
Clam
The word "clam" can be applied to freshwater mussels, and other freshwater bivalves, as well as marine bivalves.In the United States, "clam" can be used in several different ways: one, as a general term covering all bivalve molluscs...
s, and crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s, are also food sources for humans. In some areas, massive declines in shellfish
Shellfish
Shellfish is a culinary and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some kinds are found only in freshwater...
harvests have been blamed on the sea otter, and intense public debate has taken place over how to manage the competition between sea otters and humans for seafood.
The debate is complicated by the fact that sea otters have sometimes been held responsible for declines of shellfish stocks that were more likely caused by overfishing
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
by humans, disease, pollution, and seismic activity. Shellfish declines have also occurred in many parts of the North American Pacific coast that do not have sea otters, and conservationists sometimes note that the existence of large concentrations of shellfish on the coast is a recent development resulting from the fur trade's near-extirpation
Local extinction
Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...
of the sea otter. Although many factors affect shellfish stocks, sea otter predation can deplete a fishery to the point that it is no longer commercially viable. There is a consensus among scientists that sea otters and abalone fisheries cannot co-exist in the same area, and the same is likely true for certain other types of shellfish as well.
There are many facets to the interaction between sea otters and the human economy that are not as immediately felt. Sea otters have been credited with contributing to the kelp
Kelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....
harvesting industry via their well-known role in controlling sea urchin populations; kelp is used in the production of diverse food and pharmaceutical products. Although human divers harvest red sea urchin
Red sea urchin
Strongylocentrotus franciscanus, commonly called Red Sea Urchin , is a sea urchin found in the Pacific Ocean from Alaska to Baja California...
s both for food and to protect the kelp, sea otters hunt more sea urchin species and are more consistently effective in controlling these populations. The health of the kelp forest ecosystem is significant in nurturing populations of fish, including commercially important fish species. In some areas, sea otters are a popular tourist
Tourism
Tourism is travel for recreational, leisure or business purposes. The World Tourism Organization defines tourists as people "traveling to and staying in places outside their usual environment for not more than one consecutive year for leisure, business and other purposes".Tourism has become a...
attraction, bringing visitors to local hotels, restaurants, and sea otter-watching expeditions.
Role in human cultures
Amulet
An amulet, similar to a talisman , is any object intended to bring good luck or protection to its owner.Potential amulets include gems, especially engraved gems, statues, coins, drawings, pendants, rings, plants and animals; even words said in certain occasions—for example: vade retro satana—, to...
in the form of a mother with pup. Above: Aleut carving of a sea otter hunt on a whalebone spear. Both items are on display at the St. Petersburg Museum of Anthropology and Ethnography. Articles depicting sea otters were considered to have magical properties.
For many maritime indigenous cultures throughout the North Pacific, especially the Ainu
Ainu people
The , also called Aynu, Aino , and in historical texts Ezo , are indigenous people or groups in Japan and Russia. Historically they spoke the Ainu language and related varieties and lived in Hokkaidō, the Kuril Islands, and much of Sakhalin...
in the Kuril Islands, the Koryaks
Koryaks
Koryaks are an indigenous people of Kamchatka Krai in the Russian Far East, who inhabit the coastlands of the Bering Sea to the south of the Anadyr basin and the country to the immediate north of the Kamchatka Peninsula, the southernmost limit of their range being Tigilsk. They are akin to the...
and Itelmen of Kamchatka, the Aleut in the Aleutian Islands and a host of tribes on the Pacific coast of North America
Indigenous peoples of the Pacific Northwest Coast
The Indigenous peoples of the Pacific Northwest Coast are the pre-Columbian inhabitants of the Pacific Northwest Coast, their descendants, and many ethnic groups who identify with those historical peoples. They are now situated within the Canadian Province of British Columbia and the U.S...
, the sea otter has played an important role as a cultural as well as material resource. In these cultures, many of which have strongly animist traditions full of legends and stories in which many aspects of the natural world are associated with spirits, the sea otter was considered particularly kin to humans. The Nuu-chah-nulth, Haida, and other First Nations
First Nations
First Nations is a term that collectively refers to various Aboriginal peoples in Canada who are neither Inuit nor Métis. There are currently over 630 recognised First Nations governments or bands spread across Canada, roughly half of which are in the provinces of Ontario and British Columbia. The...
of coastal British Columbia used the warm and luxurious pelts as chiefs' regalia. Sea otter pelts were given in potlatch
Potlatch
A potlatch is a gift-giving festival and primary economic system practiced by indigenous peoples of the Pacific Northwest Coast of Canada and United States. This includes Heiltsuk Nation, Haida, Nuxalk, Tlingit, Makah, Tsimshian, Nuu-chah-nulth, Kwakwaka'wakw, and Coast Salish cultures...
es to mark coming-of-age ceremonies, weddings, and funerals. The Aleuts carved sea otter bones for use as ornaments and in games, and used powdered sea otter baculum
Baculum
The baculum is a bone found in the penis of most mammals. It is absent in humans, but present in other primates, such as the gorilla and chimpanzee.The bone aids in sexual intercourse.-Purpose:...
as a medicine for fever.
Yukar
are Ainu sagas that form a long rich tradition of oral literature. In older periods the epics were performed by both men and women; during the 19th and early 20th centuries, when Ainu culture was in decline, women were generally the most skillful performers....
, the Kutune Shirka
Kutune Shirka
The , known in Japanese as or simply is a sacred yukar epic of the native Ainu people of Japan. The Ainu title refers to a magic sword wielded by the story's protagonist. It is one of the most important, if not the most important, piece of Ainu literature...
, tells the tale of wars and struggles over a golden sea otter. Versions of a widespread Aleut legend tell of lovers or despairing women who plunge into the sea and become otters. These links have been associated with the many human-like behavioral features of the sea otter, including apparent playfulness, strong mother-pup bonds and tool use, yielding to ready anthropomorphism
Anthropomorphism
Anthropomorphism is any attribution of human characteristics to animals, non-living things, phenomena, material states, objects or abstract concepts, such as organizations, governments, spirits or deities. The term was coined in the mid 1700s...
. The beginning of commercial exploitation had a great impact on the human as well as animal populations – the Ainu and Aleuts have been displaced or their numbers are dwindling, while the coastal tribes of North America, where the otter is in any case greatly depleted, no longer rely as intimately on sea mammals for survival.
Since the mid-1970s, the beauty and charisma of the species have gained wide appreciation, and the sea otter has become an icon of environmental conservation. The round, expressive face and soft furry body of the sea otter are depicted in a wide variety of souvenirs, postcards, clothing, and stuffed toys.
Aquariums and zoos
Sea otters can do well in captivityCaptivity (animal)
Animals that live under human care are in captivity. Captivity can be used as a generalizing term to describe the keeping of either domesticated animals or wild animals. This may include for example farms, private homes and zoos...
, and are featured in over 40 public aquarium
Aquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
s and zoo
Zoo
A zoological garden, zoological park, menagerie, or zoo is a facility in which animals are confined within enclosures, displayed to the public, and in which they may also be bred....
s. The Seattle Aquarium
Seattle Aquarium
The Seattle Aquarium is a public aquarium opened in 1977 and located on Pier 59 on the Elliott Bay waterfront in Seattle, Washington, USA. It is accredited by the Association of Zoos and Aquariums .-History:...
became the first institution to raise sea otters from conception to adulthood with the birth of Tichuk in 1979, followed by three more pups in the early 1980s. In 2007, a YouTube
YouTube
YouTube is a video-sharing website, created by three former PayPal employees in February 2005, on which users can upload, view and share videos....
video of two sea otters holding paws drew 1.5 million viewers in two weeks, and currently has over 15 million views. Filmed five years previously at the Vancouver Aquarium
Vancouver Aquarium
The Vancouver Aquarium Marine Science Centre is a public aquarium located in Stanley Park in Vancouver, British Columbia, Canada. In addition to being a major tourist attraction for Vancouver, the aquarium is a centre for marine research, conservation and marine animal rehabilitation.The Vancouver...
, it was YouTube's most popular animal video at the time, although it has since been surpassed. The lighter-colored otter in the video is Nyac, a survivor of the 1989 Exxon Valdez oil spill
Exxon Valdez oil spill
The Exxon Valdez oil spill occurred in Prince William Sound, Alaska, on March 24, 1989, when the Exxon Valdez, an oil tanker bound for Long Beach, California, struck Prince William Sound's Bligh Reef and spilled of crude oil. It is considered to be one of the most devastating human-caused...
. Nyac died in September 2008, at the age of 20.
External links
- Field notes by Georg Wilhelm Steller, 1742 (PDF)
- Live sea otter webcam – Monterey Bay Aquarium
- Live sea otter webcam – Vancouver Aquarium
- Otters holding hands – The popular YouTube video
- Precipice of Survival: The Southern Sea Otter (video)
- Smithsonian Institution - North American Mammals: Enhydra lutris