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Sea otter

January 31, 2023

Not to be confused with the marine otter or Eurasian otter. For other uses, see Sea otter (disambiguation).

The sea otter (Enhydra lutris) 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 and 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 is capable of living exclusively in the ocean.

Sea otter
CITES Appendix II (CITES)[2][note 1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Mustelidae
Subfamily: Lutrinae
Genus: Enhydra
Species:
E. lutris
Binomial name
Enhydra lutris
Subspecies
E. l. lutris
E. l. kenyoni
E. l. nereis
Synonyms
  • Mustela lutris Linnaeus, 1758

The sea otter inhabits nearshore environments, where it dives to the sea floor to forage. It preys mostly on marine invertebrates such as sea urchins, various mollusks and crustaceans, and some species of fish. Its foraging and eating habits are noteworthy in several respects. 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 ecosystems.[3] 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 living in a fraction of their historic range.[4] A subsequent international ban on hunting, sea otter conservation efforts, and reintroduction programs into previously populated areas have contributed to numbers rebounding, and the species 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, the sea otter remains classified as an endangered species.

Evolution

The sea otter is the heaviest (the giant otter is longer, but significantly slimmer) member of the family Mustelidae,[5] a diverse group that includes the 13 otter species and terrestrial animals such as weasels, badgers, and minks. It is unique among the mustelids in not making dens or burrows, in having no functional anal scent glands,[6] and in being able to live its entire life without leaving the water.[7] The only living 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 seals.[8] Genetic analysis indicates the sea otter and its closest extant relatives, which include the African speckle-throated otter, European otter, African clawless otter and oriental small-clawed otter, shared an ancestor approximately 5 million years ago.[9]

Fossil evidence indicates the Enhydra lineage became isolated in the North Pacific approximately 2 million years ago, giving rise to the now-extinct Enhydra macrodonta and the modern sea otter, Enhydra lutris.[10] One related species has been described, Enhydra reevei, from the Pleistocene of East Anglia.[11] The modern 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.[12] In comparison to cetaceans, sirenians, and pinnipeds, which entered the water approximately 50, 40, and 20 million years ago, respectively, the sea otter is a relative newcomer to a marine existence.[13] In some respects, though, the sea otter is more fully adapted to water than pinnipeds, which must haul out on land or ice to give birth.[14] The full genome of the northern sea otter (Enhydra lutris kenyoni) was sequenced in 2017 and may allow for examination of the sea otter's evolutionary divergence from terrestrial mustelids.[15]

Taxonomy

Lutrinae

Pteronura (giant otter)

Lontra (4 species)

Enhydra (sea otter)

Hydrictis
(spotted-necked otter)

Lutra (2 species)

Aonyx
(African clawless)

Amblonyx
(Asian small-clawed)

Lutrogale
(smooth-coated)

Cladogram showing relationships between sea otters and other otters[16][17]

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 Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae.[18] Originally named Lutra marina, it underwent numerous name changes before being accepted as Enhydra lutris in 1922.[10] The generic name Enhydra, derives from the Ancient Greek en/εν "in" and hydra/ύδρα "water",[19] meaning "in the water", and the Latin word lutris, meaning "otter".[20] It was formerly sometimes referred to as the "sea beaver".[21]

Subspecies

Three subspecies of the sea otter are recognized with distinct geographical distributions. Enhydra lutris lutris (nominate), the Asian sea otter, ranges from the Kuril Islands north of Japan to Russia's Commander Islands in the western Pacific Ocean. In the eastern Pacific Ocean, E. l. kenyoni, the northern sea otter, is found from Alaska's Aleutian Islands to Oregon and E. l. nereis, the southern sea otter, is native to central and southern California.[22] The Asian sea otter is the largest subspecies and has a slightly wider skull and shorter nasal bones than both other subspecies. Northern sea otters possess longer mandibles (lower jaws) while southern sea otters have longer rostrums and smaller teeth.[23][24]

Description

 
A sea otter's thick fur makes its body appear plumper on land than in the water.
 
Skull of a sea otter

The sea otter is one of the smallest marine mammal species, but it is the heaviest mustelid.[7] Male sea otters usually weigh 22 to 45 kg (49 to 99 lb) and are 1.2 to 1.5 m (3 ft 11 in to 4 ft 11 in) in length, though specimens up to 54 kg (119 lb) have been recorded.[25] Females are smaller, weighing 14 to 33 kg (31 to 73 lb) and measuring 1.0 to 1.4 m (3 ft 3 in to 4 ft 7 in) in length.[26] For its size, the male otter's baculum is very large, massive and bent upwards, measuring 150 mm (5+7⁄8 in) in length and 15 mm (9⁄16 in) at the base.[27]

Unlike most other marine mammals, the sea otter has no blubber and relies on its exceptionally thick fur to keep warm.[28] With up to 150,000 strands of hair per square centimetre (970,000/in2), its fur is the densest of any animal.[29] The fur consists of long, waterproof guard hairs and short underfur; the guard hairs keep the dense underfur layer dry.[26] There is an air compartment between the thick fur and the skin where air is trapped and heated by the body.[30] Cold water is kept completely away from the skin and heat loss is limited.[26] However, a potential disadvantage of this form of insulation is compression of the air layer as the otter dives, thereby reducing the insulating quality of fur at depth when the animal forages.[30] The fur is thick year-round, as it is shed and replaced gradually rather than in a distinct molting season.[31] 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.[32] 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.[33] In adults, the head, throat, and chest are lighter in color than the rest of the body.[33]

The sea otter displays numerous adaptations to its marine environment. The nostrils and small ears can close.[34] The hind feet, which provide most of its propulsion in swimming, are long, broadly flattened, and fully webbed.[35] The fifth digit on each hind foot is longest, facilitating swimming while on its back, but making walking difficult.[36] 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.[37] The bones show osteosclerosis, increasing their density to reduce buoyancy.[38]

The sea otter presents an insight into the evolutionary process of the mammalian invasion of the aquatic environment, which has occurred numerous times over the course of mammalian evolution.[39] Having only returned to the sea about 3 million years ago,[40] sea otters represent a snapshot at the earliest point of the transition from fur to blubber. In sea otters, fur is still advantageous, given their small nature and division of lifetime between the aquatic and terrestrial environments.[41] However, as sea otters evolve and adapt to spending more and more of their lifetimes in the sea, the convergent evolution of blubber suggests that the reliance on fur for insulation would be replaced by a dependency on blubber. This is particularly true due to the diving nature of the sea otter; as dives become lengthier and deeper, the air layer's ability to retain heat or buoyancy decreases,[30] while blubber remains efficient at both of those functions.[41] Blubber can also additionally serve as an energy source for deep dives,[42] which would most likely prove advantageous over fur in the evolutionary future of sea otters.

 
Skull, illustration

The sea otter propels itself underwater by moving the rear end of its body, including its tail and hind feet, up and down,[35] and is capable of speeds of up to 9 kilometres per hour (5.6 mph).[5] When underwater, its body is long and streamlined, with the short forelimbs pressed closely against the chest.[43] When at the surface, it usually floats on its back and moves by sculling its feet and tail from side to side.[44] 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.[45] 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[46] – 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.[36]

Long, highly sensitive whiskers and front paws help the sea otter find prey by touch when waters are dark or murky.[47] Researchers have noted when they approach in plain view, sea otters react more rapidly when the wind is blowing towards the animals, indicating the sense of smell is more important than sight as a warning sense.[48] Other observations indicate the sea otter's sense of sight is useful above and below the water, although not as good as that of seals.[49] Its hearing is neither particularly acute nor poor.[50]

An adult's 32 teeth, particularly the molars, are flattened and rounded for crushing rather than cutting food.[51] Seals and sea otters are the only carnivores with two pairs of lower incisor teeth rather than three;[52] the adult dental formula is 3.1.3.12.1.3.2.[53] The teeth and bones are sometimes stained purple as a result of ingesting sea urchins.[54] 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 to burn the calories necessary to counteract the loss of heat due to the cold water environment.[55][56] Its digestive efficiency is estimated at 80 to 85%,[57] and food is digested and passed in as little as three hours.[28] 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 kidneys enable it to derive fresh water from sea water and excrete concentrated urine.[58]

Behavior

 
Sensitive vibrissae and forepaws enable sea otters to find prey (like this purple sea urchin) using their sense of touch.

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.[59] Foraging resumes for a few hours in the afternoon and subsides before sunset, and a third foraging period may occur around midnight.[59] Females with pups appear to be more inclined to feed at night.[59] 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.[60]

Sea otters spend much of their 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 casual observers, it appears as if the animals are scratching, but they are not known to have lice or other parasites in the fur.[61] When eating, sea otters roll in the water frequently, apparently to wash food scraps from their fur.[62]

Foraging

See also: Physiology of underwater diving

The sea otter hunts in short dives, often to the sea floor. Although it can hold its breath for up to five minutes,[34] its dives typically last about one minute and not more than four.[26] It is the only marine animal capable of lifting and turning over rocks, which it often does with its front paws when searching for prey.[62] The sea otter may also pluck snails and other organisms from kelp and dig deep into underwater mud for clams.[62] It is the only marine mammal that catches fish with its forepaws rather than with its teeth.[28]

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. This pouch also holds a rock, unique to the otter, that is used to break open shellfish and clams.[63] At the surface, 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 mussels with their shells, whereas large mussel shells may be twisted apart.[64] It uses its lower incisor teeth to access the meat in shellfish.[65] 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.[64]

The sea otter's use of rocks when hunting and feeding makes it one of the few mammal species to use tools.[66] 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.[26] Releasing an abalone, which can cling to rock with a force equal to 4,000 times its own body weight, requires multiple dives.[26]

Social structure

 
Sleeping sea otters holding paws at the Vancouver Aquarium[67] are kept afloat by their naturally high buoyancy.

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.[68] 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 kelp.[69]

A male sea otter is most likely to mate if he maintains a breeding territory in an area that is also favored by females.[70] As autumn is the peak breeding season in most areas, males typically defend their territory only from spring to autumn.[70] During this time, males patrol the boundaries of their territories to exclude other males,[70] although actual fighting is rare.[68] Adult females move freely between male territories, where they outnumber adult males by an average of five to one.[70] Males that do not have territories tend to congregate in large, male-only groups,[70] and swim through female areas when searching for a mate.[71]

The species exhibits a variety of vocal behaviors. The cry of a pup is often compared to that of a gull.[72] Females coo when they are apparently content; males may grunt instead.[73] Distressed or frightened adults may whistle, hiss, or in extreme circumstances, scream.[72] Although sea otters can be playful and sociable, they are not considered to be truly social animals.[74] They spend much time alone, and each adult can meet its own hunting, grooming, and defense needs.[74]

Reproduction and life cycle

 
While mating the male bites the nose of the female, often bloodying and scarring it.

Sea otters are polygynous: males have multiple female partners, typically those that inhabit their territory. If no territory is established, they seek out females in estrus. When a male sea otter finds a receptive female, the two engage in playful and sometimes aggressive behavior. They bond for the duration of estrus, or 3 days. The male holds the female's head or nose with his jaws during copulation. Visible scars are often present on females from this behavior.[5][75]

Births occur year-round, with peaks between May and June in northern populations and between January and March in southern populations.[76] Gestation appears to vary from four to twelve months, as the species is capable of delayed implantation followed by four months of pregnancy.[76] In California, sea otters usually breed every year, about twice as often as those in Alaska.[77]

Birth usually takes place in the water and typically produces a single pup weighing 1.4 to 2.3 kilograms (3 lb 1 oz to 5 lb 1 oz).[78] Twins occur in 2% of births; however, usually only one pup survives.[5] At birth, the eyes are open, ten teeth are visible, and the pup has a thick coat of baby fur.[79] Mothers have been observed to lick and fluff a newborn for hours; after grooming, the pup's fur retains so much air, the pup floats like a cork and cannot dive.[80] The fluffy baby fur is replaced by adult fur after about 13 weeks.[18]

 
A mother floats with her pup on her chest. Georg Steller wrote, "They embrace their young with an affection that is scarcely credible."[81]

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.[82] The milk from a sea otter's two abdominal nipples is rich in fat and more similar to the milk of other marine mammals than to that of other mustelids.[83] 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.[63] Juveniles are typically independent at six to eight months, but a mother may be forced to abandon a pup if she cannot find enough food for it;[84] at the other extreme, a pup may nurse until it is almost adult size.[78] Pup mortality is high, particularly during an individual's first winter – by one estimate, only 25% of pups survive their first year.[84] Pups born to experienced mothers have the highest survival rates.[85]

Females perform all tasks of feeding and raising offspring, and have occasionally been observed caring for orphaned pups.[86] 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.[87] When foraging, she leaves her pup floating on the water, sometimes wrapped in kelp to keep it from floating away;[88] if the pup is not sleeping, it cries loudly until she returns.[89] Mothers have been known to carry their pups for days after the pups' deaths.[81]

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.[90] A captive male sired offspring at age 19.[78] In the wild, sea otters live to a maximum age of 23 years,[26] with lifespans ranging from 10 to 15 years for males and 15–20 years for females.[91] Several captive individuals have lived past 20 years, and a female at the Seattle Aquarium died at the age of 28 years.[92] Sea otters in the wild often develop worn teeth, which may account for their apparently shorter lifespans.[93]

Population and distribution

Sea otters live in coastal waters 15 to 23 metres (49 to 75 ft) deep,[94] and usually stay within a kilometre (2⁄3 mi) of the shore.[95] They are found most often in areas with protection from the most severe ocean winds, such as rocky coastlines, thick kelp forests, and barrier reefs.[96] 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.[97] Their northern range is limited by ice, as sea otters can survive amidst drift ice but not land-fast ice.[98] Individuals generally occupy a home range a few kilometres long, and remain there year-round.[99]

The sea otter population is thought to have once been 150,000 to 300,000,[21] 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 13 colonies. Hunting records researched by historian Adele Ogden place the westernmost limit of the hunting grounds off the northern Japanese island of Hokkaido and the easternmost limit off Punta Morro Hermosa about 21+1⁄2 miles (34.6 km) south of Punta Eugenia, Baja California's westernmost headland in Mexico.[100]

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, with reports of recolonizations in Mexico and Japan.[101] Population estimates made between 2004 and 2007 give a worldwide total of approximately 107,000 sea otters.[18][102][103][104][105]

Japan

Adele Ogden wrote in The California Sea Otter Trade that sea otter were hunted "from Yezo northeastward past the Kuril Group and Kamchatka to the Aleutian Chain".[100] "Yezo" refers to the island of Hokkaido in northern Japan; the only confirmed sea otter population in Japanese territory is on the coast surrounding the town of Erimo, Hokkaido.[1]

Russia

Currently, the most stable and secure part of the sea otter's range is Russia.[106] Before the 19th century, around 20,000 to 25,000 sea otters lived near the Kuril Islands, with more near Kamchatka and the Commander Islands. After the years of the Great Hunt, the population in these areas, currently part of Russia, was only 750.[102] By 2004, sea otters had repopulated all of their former habitat in these areas, with an estimated total population of about 27,000. Of these, about 19,000 are at the Kurils, 2,000 to 3,500 at Kamchatka and another 5,000 to 5,500 at the Commander Islands.[102] Growth has slowed slightly, suggesting the numbers are reaching carrying capacity.[102]

British Columbia

Along the North American coast south of Alaska, the sea otter's range is discontinuous. A remnant population survived off Vancouver Island into the 20th century, but it died out despite the 1911 international protection treaty, with the last sea otter taken near Kyuquot in 1929. From 1969 to 1972, 89 sea otters were flown or shipped from Alaska to the west coast of Vancouver Island. This population increased to over 5,600 in 2013 with an estimated annual growth rate of 7.2%, and their range on the island's west coast extended north to Cape Scott and across the Queen Charlotte Strait to the Broughton Archipelago and south to Clayoquot Sound and Tofino.[107][108] In 1989, a separate colony was discovered in the central British Columbia coast. It is not known if this colony, which numbered about 300 animals in 2004, was founded by transplanted otters or was a remnant population that had gone undetected.[104] By 2013, this population exceeded 1,100 individuals, was increasing at an estimated 12.6% annual rate, and its range included Aristazabal Island, and Milbanke Sound south to Calvert Island.[107] In 2008, Canada determined the status of sea otters to be "special concern".[109][110]

United States

Alaska

Alaska is the central area of the sea otter's range. In 1973, the population in Alaska was estimated at between 100,000 and 125,000 animals.[111] By 2006, though, the Alaska population had fallen to an estimated 73,000 animals.[103] 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.[112] 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.[62]

Washington

In 1969 and 1970, 59 sea otters were translocated from Amchitka Island to Washington, and released near La Push and Point Grenville. The translocated population is estimated to have declined to between 10 and 43 individuals before increasing, reaching 208 individuals in 1989. As of 2017, the population was estimated at over 2,000 individuals, and their range extends from Point Grenville in the south to Cape Flattery in the north and east to Pillar Point along the Strait of Juan de Fuca.[18]

In Washington, sea otters are found almost exclusively on the outer coasts. They can swim as close as six 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 North American river otters, which are commonly seen along the seashore. However, biologists have confirmed isolated sightings of sea otters in these areas since the mid-1990s.[18]

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.[113] In 2004, a 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.[114] On 18 February 2009, a male sea otter was spotted in Depoe Bay off the Oregon Coast. It could have traveled to the state from either California or Washington.[115]

California

 
California's remote areas of coastline sheltered small colonies of sea otters through the fur trade. The 50 that survived in California, which were rediscovered in 1938, have since reproduced to almost 3,000.

The historic population of California sea otters was estimated at 16,000 before the fur trade decimated the population, leading to their assumed extinction. Today's population of California sea otters are the descendants of a single colony of about 50 sea otters located near Bixby Creek Bridge in March 1938 by Howard G. Sharpe, owner of the nearby Rainbow Lodge on Bixby Bridge in Big Sur.[116][117][118] Their principal range has gradually expanded and extends from Pigeon Point in San Mateo County to Santa Barbara County.[119]

Sea otters were once numerous in San Francisco Bay.[120][121] Historical records revealed the Russian-American Company sneaked 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.[100] The founder of Fort Ross, Ivan Kuskov, finding otters 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.[122] 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.[123] 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.[124]

In the late 1980s, the USFWS relocated about 140 southern 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 majority of the San Nicolas sea otters swam back to the mainland.[125] Another group of twenty swam 74 miles (119 km) north to San Miguel Island, where they were captured and removed.[126] By 2005, only 30 sea otters remained at San Nicolas,[127] although they were slowly increasing as they thrived on the abundant prey around the island.[125] The plan that authorized the translocation program had predicted the carrying capacity would be reached within five to 10 years.[128] The spring 2016 count at San Nicolas Island was 104 sea otters, continuing a 5-year positive trend of over 12% per year.[129] Sea otters were observed twice in Southern California in 2011, once near Laguna Beach and once at Zuniga Point Jetty, near San Diego. These are the first documented sightings of otters this far south in 30 years.[130]

When the USFWS implemented the translocation program, it also attempted, in 1986, 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 many translocated otters died and also as it proved impractical to capture the hundreds of otters which ignored regulations and swam into the zone.[131] However, after engaging in a period of public commentary in 2005, the Fish and Wildlife Service failed to release a formal decision on the issue.[127] Then, in response to lawsuits filed by the Santa Barbara-based Environmental Defense Center and the Otter Project, on 19 December 2012 the USFWS declared that the "no otter zone" experiment was a failure, and will protect the otters re-colonizing the coast south of Point Conception as threatened species.[132] Although abalone fisherman blamed the incursions of sea otters for the decline of abalone, commercial abalone fishing in southern California came to an end from overfishing in 1997, years before significant otter moved south of Point Conception. In addition, white abalone (Haliotis sorenseni), a species never overlapping with sea otter, had declined in numbers 99% by 1996, and became the first marine invertebrate to be federally listed as endangered.[133]

Although the southern sea otter's range has continuously expanded from the remnant population of about 50 individuals in Big Sur since protection in 1911, from 2007 to 2010, the otter population and its range contracted and since 2010 has made little progress.[134][135] As of spring 2010, the northern boundary had moved from about Tunitas Creek to a point 2 kilometres (1.2 mi) southeast of Pigeon Point, and the southern boundary has moved along the Gaviota Coast from approximately Coal Oil Point to Gaviota State Park.[136] A toxin called microcystin, produced by a type of cyanobacteria (Microcystis), seems to be concentrated in the shellfish the otters eat, poisoning them. Cyanobacteria are found in stagnant water 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.[137][138] 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.[139] Great white sharks do not consume relatively fat-poor sea otters but shark-bitten carcasses have increased from 8% in the 1980s to 15% in the 1990s and to 30% in 2010 and 2011.[140]

For southern sea otters to be considered for removal from threatened species listing, the U.S. Fish and Wildlife Service (USFWS) determined that the population should exceed 3,090 for three consecutive years.[134] In response to recovery efforts, the population climbed steadily from the mid-20th century through the early 2000s, then remained relatively flat from 2005 to 2014 at just under 3,000. There was some contraction from the northern (now Pigeon Point) and southern limits of the sea otter's range during the end of this period, circumstantially related to an increase in lethal shark bites, raising concerns that the population had reached a plateau.[141] However, the population increased markedly from 2015 to 2016, with the United States Geological Survey (USGS) California sea otter survey 3-year average reaching 3,272 in 2016, the first time it exceeded the threshold for delisting from the Endangered Species Act (ESA).[129] If populations continued to grow and ESA delisting occurred, southern sea otters would still be fully protected by state regulations and the Marine Mammal Protection Act, which set higher thresholds for protection, at approximately 8,400 individuals.[142] However, ESA delisting seems unlikely due to a precipitous population decline recorded in the spring 2017 USGS sea otter survey count, from the 2016 high of 3,615 individuals to 2,688, a loss of 25% of the California sea otter population.[143]

Mexico

Historian Adele Ogden described sea otters are particularly abundant in "Lower California", now the Baja California Peninsula, where "seven bays...were main centers". The southernmost limit was Punta Morro Hermoso about 21+1⁄2 miles (34.6 km) south of Punta Eugenia, in turn a headland at the southwestern end of Sebastián Vizcaíno Bay, on the west coast of the Baja Peninsula. Otter were also taken from San Benito Island, Cedros Island, and Isla Natividad in the Bay.[100] By the early 1900s, Baja's sea otters were extirpated by hunting. In a 1997 survey, small numbers of sea otters, including pups, were reported by local fishermen, but scientists could not confirm these accounts.[144] However, male and female otters have been confirmed by scientists off shores of the Baja Peninsula in a 2014 study, who hypothesize that otter dispersed there beginning in 2005. These sea otters may have dispersed from San Nicolas Island, which is 300 kilometres (190 mi) away, as individuals have been recorded traversing distances of over 800 kilometres (500 mi). Genetic analysis of most of these animals were consistent with California, i.e. United States, otter origins, however one otter had a haplotype not previously reported, and could represent a remnant of the original native Mexican otter population.[145]

Ecology

Diet

High energetic requirements of sea otter metabolism require them to consume at least 20% of their body weight a day.[30] Surface swimming and foraging are major factors in their high energy expenditure due to drag on the surface of the water when swimming and the thermal heat loss from the body during deep dives when foraging.[146][30] Sea otter muscles are specially adapted to generate heat without physical activity.[147]

Sea otters consume over 100 prey species.[148] In most of its range, the sea otter's diet consists almost exclusively of marine benthic invertebrates, including sea urchins, fat innkeeper worms, a variety of bivalves such as clams and mussels, abalone, other mollusks, crustaceans, and snails.[148][149] Its prey ranges in size from tiny limpets and crabs to giant octopuses.[148] 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.[148] In California, they have been noted to ignore Pismo clams smaller than 3 inches (76 mm) across.[150]

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.[151] The fish species were usually bottom-dwelling and sedentary or sluggish forms, such as Hemilepidotus hemilepidotus and family Tetraodontidae.[151] However, south of Alaska on the North American coast, fish are a negligible or extremely minor part of the sea otter's diet.[18][152] Contrary to popular depictions, sea otters rarely eat starfish, and any kelp that is consumed apparently passes through the sea otter's system undigested.[153]

The individuals within a particular area often differ in their foraging methods and prey types, and tend to follow the same patterns as their mothers.[154] 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.[18] Sea otters can thoroughly remove abalone from an area except for specimens in deep rock crevices,[155] however, they never completely wipe out a prey species from an area.[156] A 2007 Californian study demonstrated, in areas where food was relatively scarce, a wider variety of prey was consumed. Surprisingly, though, the diets of individuals were more specialized in these areas than in areas where food was plentiful.[125]

As a keystone species

 
Sea otters control herbivore populations, ensuring sufficient coverage of kelp in kelp forests

Sea otters are a classic example of a keystone species; their presence affects the ecosystem more profoundly than their size and numbers would suggest. They keep the population of certain benthic (sea floor) herbivores, particularly sea urchins, in check.[3] Sea urchins graze on the lower stems of kelp, causing the kelp to drift away and die.[157] Loss of the habitat and nutrients provided by kelp forests leads to profound cascade effects on the marine ecosystem. North Pacific areas that do not have sea otters often turn into urchin barrens, with abundant sea urchins and no kelp forest.[5] Kelp forests are extremely productive ecosystems. Kelp forests sequester (absorb and capture) CO2 from the atmosphere through photosynthesis. Sea otters may help mitigate effects of climate change by their cascading trophic influence[158]

Reintroduction of sea otters to British Columbia has led to a dramatic improvement in the health of coastal ecosystems,[159] and similar changes have been observed as sea otter populations recovered in the Aleutian and Commander Islands and the Big Sur coast of California[160] However, some kelp forest ecosystems in California have also thrived without sea otters, with sea urchin populations apparently controlled by other factors.[160] 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.[160]

Sea otters affect rocky ecosystems that are dominated by mussel beds by removing mussels from rocks. This allows space for competing species and increases species diversity.[160]

Predators

Leading mammalian predators of this species include orcas and sea lions, and bald eagles may grab pups from the surface of the water. Young predators may kill an otter and not eat it.[66] On land, young sea otters may face attack from bears and coyotes. In California, great white sharks are their primary predator[161] but there is no evidence that the sharks eat them.

Urban runoff transporting cat feces into the ocean brings Toxoplasma gondii, an obligate parasite of felids, which has killed sea otters.[162] Parasitic infections of Sarcocystis neurona are also associated with human activity.[15] According to the U.S. Geological Survey and the CDC, northern sea otters off Washington have been infected with the H1N1 flu virus and "may be a newly identified animal host of influenza viruses".[163]

Relationship with humans

Fur trade

 
Aleut men in Unalaska in 1896 used waterproof kayak gear and garments to hunt sea otters.

Sea otters have the thickest fur of any mammal, which makes them a common 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.[21]

In the early 18th century, Russians began to hunt sea otters in the Kuril Islands[21] and sold them to the Chinese at Kyakhta. 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 he 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 1,000 sea otters, and were able to command high prices for the pelts.[164] Thus began what is sometimes called the "Great Hunt", which would continue for another hundred years. The Russians found the sea otter far more valuable than the sable skins that had driven and paid for most of their expansion across Siberia. If the sea otter pelts brought back by Bering's survivors had been sold at Kyakhta prices they would have paid for one tenth the cost of Bering's expedition.[165]

 
Pelt sales (in thousands) in the London fur market – the decline beginning in the 1880s reflects dwindling sea otter populations.[166]

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 the hunters had introduced.[167][disputed – discuss] The Aleut population was reduced, by the Russians' own estimate, from 20,000 to 2,000.[168] By the 1760s, the Russians had reached Alaska. In 1799, Tsar 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 Aleksander 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; in 1818, the indigenous peoples of Alaska were granted civil rights equivalent to a townsman status in the Russian Empire.[169]

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.[167] 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.[170]

Russian hunting expanded to the south, initiated by American ship captains, who subcontracted Russian supervisors and Aleut hunters[171] in what are 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 and 1846.[172] In 1812, the Russians founded an agricultural settlement at what is now Fort Ross in northern California, as their southern headquarters.[170] Eventually, sea otter populations became so depleted, commercial hunting was no longer viable. It had stopped in the Aleutian Islands, by 1808, as a conservation measure imposed by the Russian-American Company. Further restrictions were ordered by the company in 1834.[173] 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.[174] Prices rose as the species became rare. During the 1880s, a pelt brought $105 to $165 in the London market, but by 1903, a pelt could be worth as much as $1,125.[78] 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.[175] So few remained, perhaps only 1,000–2,000 individuals in the wild, that many believed the species would become extinct.[18]

Recovery and conservation

Main article: Sea otter conservation
 
In the wake of the March 1989 Exxon Valdez oil spill, heavy sheens of oil covered large areas of Prince William Sound.

During the 20th century, sea otter numbers rebounded in about two-thirds of their historic range, a recovery considered one of the greatest successes in marine conservation.[176] 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 orcas, poaching, and conflicts with fisheries – sea otters can drown if entangled in fishing gear.[1] The hunting of sea otters is no longer legal except for limited harvests by indigenous peoples in the United States.[177] 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.[106]

The most significant threat to sea otters is oil spills,[66] to which they are particularly vulnerable, since they rely on their fur to keep warm. When their fur is soaked with oil, it loses its ability to retain air, and the animals can quickly die from hypothermia.[66] The liver, kidneys, and lungs of sea otters also become damaged after they inhale oil or ingest it when grooming.[66] 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.[178] Describing the public sympathy for sea otters that developed from media coverage of the event, a U.S. Fish and Wildlife Service spokesperson wrote:

As a playful, photogenic, innocent bystander, the sea otter epitomized the role of victim ... cute and frolicsome sea otters suddenly in distress, oiled, frightened, and dying, in a losing battle with the oil.[18]

The small geographic ranges of the sea otter populations in California, Washington, and British Columbia mean a single major spill could be catastrophic for that state or province.[18][56][62] Prevention of oil spills and preparation to rescue otters if one happens is a major focus for conservation efforts. Increasing the size and range of sea otter populations would also reduce the risk of an oil spill wiping out a population.[18] 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.[179]

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.[180] The most widely accepted, but still controversial, hypothesis is that killer whales have been eating the otters. The pattern of disappearances is consistent with a rise in predation, but there has been no direct evidence of orcas preying on sea otters to any significant extent.[112]

Another area of concern is California, where recovery began to fluctuate or decline in the late 1990s.[181] Unusually high mortality rates amongst adult and subadult otters, particularly females, have been reported.[105] In 2017 the US Geological Survey found a 3% drop in the sea otter population of the California coast. This number still keeps them on track for removal from the endangered species list, although just barely.[182] Necropsies of dead sea otters indicate diseases, particularly Toxoplasma gondii and acanthocephalan parasite infections, are major causes of sea otter mortality in California.[183] The Toxoplasma gondii parasite, which is often fatal to sea otters, is carried by wild and domestic cats and may be transmitted by domestic cat droppings flushed into the ocean via sewage systems.[183][184] Although disease has clearly contributed to the deaths of many of California's sea otters, it is not known why the California population is apparently more affected by disease than populations in other areas.[183]

 
Sea otters off the coast of Washington, within the Olympic Coast National Marine Sanctuary

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.[185] An estimated 1,200 sea otters live within the Monterey Bay National Marine Sanctuary, and more than 500 live within the Olympic Coast National Marine Sanctuary.[186][187]

Economic impact

Some of the sea otter's preferred prey species, particularly abalone, clams, and crabs, 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.[188]

The debate is complicated because sea otters have sometimes been held responsible for declines of shellfish stocks that were more likely caused by overfishing, disease, pollution, and seismic activity.[62][189] Shellfish declines have also occurred in many parts of the North American Pacific coast that do not have sea otters, and conservationists sometimes note 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.[189] Although many factors affect shellfish stocks, sea otter predation can deplete a fishery to the point where it is no longer commercially viable.[188] Scientists agree that sea otters and abalone fisheries cannot exist in the same area,[188] and the same is likely true for certain other types of shellfish, as well.[180]

Many facets of the interaction between sea otters and the human economy 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.[190] Although human divers harvest red sea urchins both for food and to protect the kelp, sea otters hunt more sea urchin species and are more consistently effective in controlling these populations.[191] E. lutris is a controlling predator of the red king crab (Paralithodes camtschaticus) in the Bering Sea, which would otherwise be out of control as it is in its invasive range, the Barents Sea.[192] (Berents otters, Lutra lutra, occupy the same ecological niche and so are believed to help to control them in the Berents but this has not been studied.)[192] The health of the kelp forest ecosystem is significant in nurturing populations of fish, including commercially important fish species.[190] In some areas, sea otters are popular tourist attractions, bringing visitors to local hotels, restaurants, and sea otter-watching expeditions.[190]

Roles in human cultures

 
 

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 Peter the Great Museum of Anthropology and Ethnography in St. Petersburg. Articles depicting sea otters were considered to have magical properties.[193]

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, the Haida of Haida Gwaii[194] 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 potlatches to mark coming-of-age ceremonies, weddings, and funerals.[67] The Aleuts carved sea otter bones for use as ornaments and in games, and used powdered sea otter baculum as a medicine for fever.[195]

Among the Ainu, the otter is portrayed as an occasional messenger between humans and the creator.[196] 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.[197] 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.[198] 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.[199]

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.[181] 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.[200]

Aquariums and zoos

Sea otters can do well in captivity, and are featured in over 40 public aquariums and zoos.[201] 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.[202] In 2007, a YouTube video of two sea otters holding paws drew 1.5 million viewers in two weeks, and had over 22 million views as of July 2022.[203] 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.[204] Nyac died in September 2008, at the age of 20.[205] Milo, the darker one, died of lymphoma in January 2012.[206]

Current Conservation

Sea otters, being a known keystone species, need a humanitarian effort to be protected from endangerment through "unregulated human exploitation".[207] This species has increasingly been impacted by the large oil spills and environmental degradation caused by overfishing and entanglement in fishing gear.[208] Current efforts have been made in legislation: the international Fur Seal Treaty, The Endangered Species Act, IUCN/The World Conservation Union, Convention on international Trade in Endangered Species of Wild Fauna and Flora, Marine Mammal Protection Act of 1972. Other conservation efforts are done through reintroduction and zoological parks. International Fur Seal Treaty:

The Endangered Species Act:

IUCN/The World Conservation Union:

Convention on international Trade in Endangered Species of Wild Fauna and Flora:

Marine Mammal Protection Act of 1972:

See also

Notes

  1. ^ Enhydra lutris nereis is included in Appendix I

References

Citations

  1. ^ a b c Doroff, A.; Burdin, A. (2015). "Enhydra lutris". IUCN Red List of Threatened Species. 2015: e.T7750A21939518. doi:10.2305/IUCN.UK.2015-2.RLTS.T7750A21939518.en. Retrieved 11 November 2021.
  2. ^ "Appendices | CITES". cites.org. Retrieved 14 January 2022.
  3. ^ a b Womble, Jamie (29 July 2016). "A Keystone Species, the Sea Otter, Colonizes Glacier Bay". National Park Service. Retrieved 23 November 2021.
  4. ^ Riedman, M.L.; Estes, James A. (1990). The sea otter (Enhydra lutris): behavior, ecology, and natural history. U.S. Fish and Wildlife Service Biological Report (Report). Washington, D.C. p. 126. Retrieved 27 September 2010.
  5. ^ a b c d e "Enhydra lutris". Animal Diversity Web. University of Michigan Museum of Zoology. Retrieved 24 November 2007.
  6. ^ Kenyon, p. 4
  7. ^ a b VanBlaricom, p. 11
  8. ^ Koepfli, K.-P.; Wayne, R. K. (December 1998). "Phylogenetic relationships of otters (Carnivora: Mustelidae) based on mitochondrial cytochrome b sequences". Journal of Zoology. 246 (4): 401–416. doi:10.1111/j.1469-7998.1998.tb00172.x.
  9. ^ Koepfli KP; Deere KA; Slater GJ; et al. (2008). "Multigene phylogeny of the Mustelidae: resolving relationships, tempo and biogeographic history of a mammalian adaptive radiation". BMC Biology. 6: 10. doi:10.1186/1741-7007-6-10. PMC 2276185. PMID 18275614.
  10. ^ a b Love, p. 9
  11. ^ Willemsen GF (1992). "A revision of the Pliocene and Quaternary Lutrinae from Europe". Scripta Geologica. 101: 1–115. CiteSeerX 10.1.1.738.4492.
  12. ^ Love, pp. 15–16
  13. ^ Love, pp. 4–6
  14. ^ Love, p. 6
  15. ^ a b Jones, Samantha J; Haulena, Martin; Taylor, Gregory A; Chan, Simon; Bilobram, Steven; Warren, René L; Hammond, Austin; Mungall, Karen L; Choo, Caleb; et al. (11 December 2017). "The Genome of the Northern Sea Otter (Enhydra lutris kenyoni)". Genes. 8 (12): 379. doi:10.3390/genes8120379. PMC 5748697. PMID 29232880.
  16. ^ Koepfli KP, Deere KA, Slater GJ, et al. (2008). "Multigene phylogeny of the Mustelidae: Resolving relationships, tempo and biogeographic history of a mammalian adaptive radiation". BMC Biol. 6: 4–5. doi:10.1186/1741-7007-6-10. PMC 2276185. PMID 18275614.
  17. ^ Bininda-Emonds OR, Gittleman JL, Purvis A (1999). "Building large trees by combining phylogenetic information: a complete phylogeny of the extant Carnivora (Mammalia)" (PDF). Biol Rev Camb Philos Soc. 74 (2): 143–75. CiteSeerX 10.1.1.328.7194. doi:10.1017/S0006323199005307. PMID 10396181.
  18. ^ a b c d e f g h i j k (PDF). Washington Department of Fish and Wildlife. (link: WDFW seaotter). Archived from the original (PDF) on 10 July 2018. Retrieved 10 July 2018.
  19. ^ Liddell, Henry George and Robert Scott (1980). A Greek-English Lexicon (Abridged ed.). United Kingdom: Oxford University Press. ISBN 978-0-19-910207-5. OCLC 17396377.
  20. ^ Nickerson, p. 19
  21. ^ a b c d Silverstein, p. 34
  22. ^ Campbell, Kristin M.; Santana, Sharlene E. (3 October 2017). "Do differences in skull morphology and bite performance explain dietary specialization in sea otters?" (PDF). Journal of Mammalogy. 98: 1408. doi:10.1093/jmammal/gyx091. S2CID 91055290 – via Oxford University Press.
  23. ^ Wilson, Don E.; Bogan, Michael A.; Brownell, Robert L.; Burdin, A. M.; Maminov, M. K. (13 February 1991). "Geographic Variation in Sea Otters, Enhydra lutris". Journal of Mammalogy. 72 (1): 22–36. doi:10.2307/1381977. JSTOR 1381977 – via University of Nebraska – Lincoln.
  24. ^ Timm-Davis, Lori L.; DeWitt, Thomas J.; Marshall, Christopher D. (9 December 2015). "Divergent Skull Morphology Supports Two Trophic Specializations in Otters (Lutrinae)". PLOS ONE. 10 (12): 7. Bibcode:2015PLoSO..1043236T. doi:10.1371/journal.pone.0143236. PMC 4674116. PMID 26649575.
  25. ^ The Wildlife Year. The Reader's Digest Association, Inc. (1991). ISBN 0-276-42012-8
  26. ^ a b c d e f g "Sea Otters, Enhydra lutris". MarineBio.org. 18 May 2017. Retrieved 30 August 2020.
  27. ^ Heptner, V. G.; Sludskii, A. A. (2002). Mammals of the Soviet Union. Vol. II, part 1b, Carnivores (Mustelidae and Procyonidae). Washington, D.C. : Smithsonian Institution Libraries and National Science Foundation. p. 1342. ISBN 978-90-04-08876-4.
  28. ^ a b c Nickerson, p. 21
  29. ^ Silverstein, p. 14
  30. ^ a b c d e Yeates, Laura (2007). "Diving and foraging energetics of the smallest marine mammal, the sea otter (Enhydra lutris)". Journal of Experimental Biology. 210 (Pt 11): 1960–1970. doi:10.1242/jeb.02767. PMID 17515421. S2CID 21944946.
  31. ^ Kenyon, pp. 37–39
  32. ^ Love, p. 21 and 28
  33. ^ a b Love, p. 27
  34. ^ a b Silverstein, p. 13
  35. ^ a b Love, p. 21
  36. ^ a b Kenyon, p. 70
  37. ^ Silverstein, p. 11
  38. ^ Hayashi, S.; Houssaye, A.; Nakajima, Y.; Chiba, K.; Ando, T.; Sawamura, H.; Inuzuka, N.; Kaneko, N.; Osaki, T. (2013). "Bone Inner Structure Suggests Increasing Aquatic Adaptations in Desmostylia (Mammalia, Afrotheria)". PLOS ONE. 8 (4): e59146. Bibcode:2013PLoSO...859146H. doi:10.1371/journal.pone.0059146. PMC 3615000. PMID 23565143.
  39. ^ Yuan, Yuan; Zhang, Yaolei; Zhang, Peijun; Liu, Chang; Wang, Jiahao; Gao, Haiyu; Hoelzel, A. Rus; Seim, Inge; Lv, Meiqi; Lin, Mingli; Dong, Lijun; Gao, Haoyang; Yang, Zixin; Caruso, Francesco; Lin, Wenzhi (14 September 2021). "Comparative genomics provides insights into the aquatic adaptations of mammals". Proceedings of the National Academy of Sciences. 118 (37): e2106080118. Bibcode:2021PNAS..11806080Y. doi:10.1073/pnas.2106080118. ISSN 0027-8424. PMC 8449357. PMID 34503999.
  40. ^ Liwanag, Heather (December 2012). "Morphological and thermal properties of mammalian insulation: the evolutionary transition to blubber in pinnipeds". Biological Journal of the Linnean Society. 107 (4): 774–787. doi:10.1111/j.1095-8312.2012.01992.x.
  41. ^ a b Liwanag, Heather (2008). "Fur versus Blubber: A comparative look at marine mammal insulation and its metabolic and behavioral consequences". Thesis at Cal Poly State University.
  42. ^ Koopman, Heather N. (7 March 2018). "Function and evolution of specialized endogenous lipids in toothed whales". The Journal of Experimental Biology. 221 (Pt Suppl 1): jeb161471. doi:10.1242/jeb.161471. ISSN 1477-9145. PMID 29514890. S2CID 3789040.
  43. ^ Kenyon, p. 62
  44. ^ Love, p. 22
  45. ^ VanBlaricom, p. 64
  46. ^ . Archived from the original on 8 December 2008. Retrieved 23 February 2008.
  47. ^ VanBlaricom, p. 11 and 21
  48. ^ Kenyon, p. 55
  49. ^ Love, p. 23
  50. ^ Kenyon, p. 56
  51. ^ Kenyon, p. 43
  52. ^ Love, p. 74
  53. ^ Kenyon, p. 47
  54. ^ Winer, J.N.; Liong, S.M.; Verstraete, F.J.M. (2013). "The Dental Pathology of Southern Sea Otters (Enhydra lutris nereis)". Journal of Comparative Pathology. 149 (2–3): 346–355. doi:10.1016/j.jcpa.2012.11.243. PMID 23348015.
  55. ^ VanBlaricom, p. 17
  56. ^ a b (PDF). British Columbia Ministry of Environment, Lands and Parks. October 1993. Archived from the original (PDF) on 16 February 2008. Retrieved 13 December 2007.
  57. ^ Love, p.24
  58. ^ Ortiz RM (June 2001). "Osmoregulation in marine mammals". The Journal of Experimental Biology. 204 (11): 1831–44. doi:10.1242/jeb.204.11.1831. PMID 11441026.
  59. ^ a b c Love, pp. 69–70
  60. ^ Love, pp. 70–71
  61. ^ Kenyon, p. 76
  62. ^ a b c d e f Reitherman, Bruce (1993). Waddlers and Paddlers: A Sea Otter Story–Warm Hearts & Cold Water (Documentary). U.S.A.: PBS.
  63. ^ a b Haley, D., ed. (1986). "Sea Otter". Marine Mammals of Eastern North Pacific and Arctic Waters (2nd ed.). Seattle, Washington: Pacific Search Press. ISBN 978-0-931397-14-1. OCLC 13760343.
  64. ^ a b VanBlaricom, p. 22
  65. ^ "Sea otter". BBC. Retrieved 31 December 2007.
  66. ^ a b c d e "Sea otter AquaFact file". Vancouver Aquarium Marine Science Centre. Retrieved 5 December 2007.
  67. ^ a b Okerlund, Lana (4 October 2007). "Too Many Sea Otters?". Retrieved 15 January 2007.
  68. ^ a b Love, p. 49
  69. ^ VanBlaricom, p. 45
  70. ^ a b c d e VanBlaricom, pp. 42–45
  71. ^ Love, p. 50
  72. ^ a b Kenyon, p. 77
  73. ^ Kenyon, pp. 78–79
  74. ^ a b Silverstein, p. 61
  75. ^ At least one female is known to have died from an infected nose. (Love, p. 52)
  76. ^ a b Love, p. 54
  77. ^ Silverstein, p. 30
  78. ^ a b c d Nowak, Roland M. (1991). Walker's Mammals of the World Volume II (Fifth ed.). Baltimore and London: The Johns Hopkins University Press. pp. 1141–1143. ISBN 978-0-8018-3970-2.
  79. ^ Kenyon, p.44
  80. ^ Love, pp. 56–61
  81. ^ a b Love, p. 58
  82. ^ Silverstein, pp. 31–32
  83. ^ Love, p. 61
  84. ^ a b Love, p. 63
  85. ^ Love, p. 62
  86. ^ Love, p. 59
  87. ^ Kenyon, p. 89
  88. ^ Silverstein, p. 31
  89. ^ Silverstein, p. 28
  90. ^ Love, p. 53
  91. ^ VanBlaricom, p. 71
  92. ^ VanBlaricom, pp. 40–41
  93. ^ VanBlaricom, p. 41
  94. ^ Silverstein, p. 17
  95. ^ Nickerson, p. 49
  96. ^ Silverstein, p. 19
  97. ^ VanBlaricom, p. 14
  98. ^ Kenyon, p. 133
  99. ^ Love, pp. 67–69
  100. ^ a b c d Ogden, Adele (1975). The California sea otter trade, 1784–1848. Berkeley, California: University of California Press. p. 54. ISBN 978-0-520-02806-7.
  101. ^ VanBlaricom, p. 54
  102. ^ a b c d Kornev S.I., Korneva S.M. (2004) Population dynamics and present status of sea otters (Enhydra lutris) of the Kuril Islands and southern Kamchatka. Marine Mammals of the Holarctic, Proceedings of 2004 conference. pp. 273–278.
  103. ^ a b . U.S. Fish and Wildlife Service – Alaska. Archived from the original on 6 February 2008. Retrieved 15 January 2008.
  104. ^ a b Barrett-Lennard, Lance (20 October 2004). . Vancouver Aquarium. Archived from the original on 17 September 2006. Retrieved 11 December 2007.
  105. ^ a b Leff, Lisa (15 June 2007). . Associated Press. Archived from the original on 8 January 2011. Retrieved 25 December 2007.
  106. ^ a b VanBlaricom, p. 62
  107. ^ a b "Trends in the Abundance and Distribution of Sea Otters (Enhydra lutris) in British Columbia Updated with 2013 Survey Results" (PDF). Department of Fisheries and Oceans, Canada. July 2015. Retrieved 10 July 2018.
  108. ^ "Sea Otter Recovery on Vancouver Island's West Coast". Bamfield Marine Sciences Centre Public Education Programme. Retrieved 22 August 2011.
  109. ^ Sea Otter, Species at Risk Public Registry
  110. ^ Sea Otters, Fisheries and Oceans Canada
  111. ^ Nickerson, p. 46
  112. ^ a b Schrope M (February 2007). "Food chains: killer in the kelp". Nature. 445 (7129): 703–5. Bibcode:2007Natur.445..703S. doi:10.1038/445703a. PMID 17301765. S2CID 4421362.
  113. ^ Jameson, Ronald James (1975). An Evaluation of Attempts to Reestablish the Sea Otter in Oregon (PDF) (MSc). Oregon State University. OCLC 9653603. Archived from the original (PDF) on 25 May 2017. Retrieved 30 December 2009.
  114. ^ Quinn, Beth (17 October 2004). (PDF). The Oregonian. Archived from the original (PDF) on 30 December 2010. Retrieved 30 December 2009.
  115. ^ "Rare sea otter confirmed at Depoe Bay". The Oregonian. 20 February 2009. Retrieved 27 February 2009.
  116. ^ Williams, Honey. "Redwood Sanctuary" (PDF). Retrieved 18 December 2017.
  117. ^ Hathaway, Pat. "Bixby Creek Bridge on Highway One from the Pat Hathaway Photo Collection". caviews.com. Retrieved 18 December 2017.
  118. ^ Silverstein, p. 41
  119. ^ "Spring 2007 Mainland California Sea Otter Survey Results". U.S. Geological Survey. 30 May 2007. Retrieved 23 February 2008.
  120. ^ Rogers, Paul (11 December 2020). "Are sea otters taking a bite out of California's Dungeness crab season?". The Mercury News. Retrieved 12 December 2020.
  121. ^ Southern Sea Otters 30 November 2011 at the Wayback Machine. nrdc.org
  122. ^ Bancroft, Hubert Howe; Bates, Alfred; Petroff, Ivan; Nemos, William (1887). History of Alaska: 1730–1885. San Francisco, California: A. L. Bancroft & Company. p. 482. Retrieved 26 September 2010.
  123. ^ Stewart, Suzanne; Praetzellis, Adrian (November 2003). Archeological Research Issues for the Point Reyes National Seashore – Golden Gate National Recreation Area (PDF) (Report). Anthropological Studies Center, Sonoma State University. p. 335. Retrieved 26 September 2010.
  124. ^ Battersby, Bob; Maginis, Preston; Nielsen, Susan; Scales, Gary; Torney, Richard; Wynne, Ed (May 2008). Ross, California – The people, the places, the history. Ross Historical Society. Retrieved 3 November 2010.
  125. ^ a b c University of California – Santa Cruz (18 January 2008). "Sea Otter Show Striking Variability in Diets And Feeding Strategies". ScienceDaily. Retrieved 20 January 2008.
  126. ^ mcLeish, p. 32
  127. ^ a b "U.S. Fish and Wildlife Service Proposes that Southern Sea Otter Translocation Program be Terminated" (PDF). U.S. Fish and Wildlife Service. 5 October 2005. Retrieved 10 April 2008.
  128. ^ "Service Proposes to End Southern Sea Otter Translocation Program". USFWS Pacific Southwest Region. 17 August 2011. Retrieved 21 December 2012.
  129. ^ a b Hatfield, B.B.; Tinker, M.T. (19 September 2016). Annual California Sea Otter Census – 2016 Spring Census Summary. USGS Western Ecological Research Center (Report). doi:10.5066/F7FJ2DWJ.
  130. ^ . KABC-TV/DT. 7 December 2011. Archived from the original on 21 October 2013. Retrieved 8 December 2011.
  131. ^ "Balance sought in sea otter conflict". CNN. 24 March 1999. Retrieved 25 January 2008.
  132. ^ Weiss, Kenneth R. (20 December 2012). "U.S. will let otters roam along Southern California coastline". Los Angeles Times. Retrieved 21 December 2012.
  133. ^ mcLeish, p. 264
  134. ^ a b "California's Sea Otter Numbers Continue Slow Climb". USGS. 12 September 2013. Retrieved 20 October 2013.
  135. ^ Young Landis, Ben; Tinker, Tim; Hatfield, Brian (3 August 2010). "California Sea Otter Numbers Drop Again". U. S. Geological Survey. Retrieved 23 January 2011.
  136. ^ "Spring 2010 Mainland California Sea Otter Survey Results". USGS Western Ecological Research Center. Retrieved 26 September 2010.
  137. ^ Weiss, Kenneth R. (23 September 2010). "Another deadly challenge for the sea otter". Los Angeles Times. Retrieved 10 November 2010.
  138. ^ Miller MA; Kudela RM; Mekebri A; Crane D; Oates SC; et al. (2010). Thompson, Ross (ed.). "Evidence for a Novel Marine Harmful Algal Bloom: Cyanotoxin (Microcystin) Transfer from Land to Sea Otters". PLOS ONE. 5 (9): e12576. Bibcode:2010PLoSO...512576M. doi:10.1371/journal.pone.0012576. PMC 2936937. PMID 20844747.
  139. ^ Colliver, Victoria (23 January 2011). "Sea otter deaths jump in 2010". San Francisco Chronicle. Retrieved 23 January 2011.
  140. ^ USGS (April 2012). "Number of dead California sea otters a record high in 2011". Marine Pollution Bulletin. 64 (4): 671–674. doi:10.1016/j.marpolbul.2012.03.002.
  141. ^ Hatfield, Brian; Tinker, Tim (22 September 2014). Spring 2014 California Sea Otter Census Results (Report). Retrieved 6 December 2015.
  142. ^ "Southern Sea Otter". USFWS, Ventura Fish and Wildlife Office. Retrieved 28 December 2016.
  143. ^ Tinker, M. T.; Hatfield, B. B. (29 September 2017). "California sea otter (Enhydra lutris nereis) census results, Spring 2017". California sea otter (Enhydra lutris nereis) census results, spring 2017 (Report). Data Series. U.S. Geological Survey Data Series 1067. p. 9. doi:10.3133/ds1067.
  144. ^ Gallo-Reynoso JP, Rateibun GB (1997). "Status of Sea Otters (Enhydra Lutris) in Mexico". Marine Mammal Science. 13 (2): 332–340. doi:10.1111/j.1748-7692.1997.tb00639.x.
  145. ^ Schramm Y, Heckel G, Sáenz-Arroyo A, López-Reyes E, Baez-Flores A, Gómez-Hernández G, Lazode-la-Vega-Trinker A, Lubinsky-Jinich D, de los Angeles Milanés-Salinas M (2014). "New evidence for the existence of southern sea otters (Enhydra lutris nereis) in Baja California, Mexico". Marine Mammal Science. 30 (3): 1264–1271. doi:10.1111/mms.12104.
  146. ^ Williams, Terrie (1989). "Swimming by sea otters: adaptations for low energetic cost locomotion". Journal of Comparative Physiology A. 164 (6): 815–824. doi:10.1007/BF00616753. PMID 2724187. S2CID 1926452.
  147. ^ Wright, Traver; Sheffield-Moore, Melinda; Davis, Randall (2 December 2021). "Sea otters demonstrate that there is more to muscle than just movement – it can also bring the heat". The Conversation. Retrieved 8 December 2021.
  148. ^ a b c d VanBlaricom pp. 18–29
  149. ^ . elkhornslough.org
  150. ^ Love, p. 96
  151. ^ a b Kenyon, p. 121
  152. ^ Love, p. 76
  153. ^ Kenyon, p. 119
  154. ^ VanBlaricom, p. 29
  155. ^ VanBlaricom, p. 30
  156. ^ Nickerson, p. 57
  157. ^ Chrobak, Ula (15 September 2021). "How sea otters can fight climate change". BBC. Retrieved 11 December 2021.
  158. ^ Sezen, Uzay (29 May 2017). "Otters vs. Climate Change – KQED/QUEST (2014)". Nature Documentaries. Retrieved 6 June 2017.
  159. ^ . Fisheries and Oceans Canada. Archived from the original on 23 November 2007. Retrieved 29 November 2007.
  160. ^ a b c d VanBlaricom, p. 33
  161. ^ Nickerson, P. . Defenders of Wildlife. p. 65. Archived from the original on 9 July 2011. Retrieved 31 August 2011.
  162. ^ "Parasite Shed in Cat Feces Kills Sea Otters – California Sea Grant" (PDF). www-csgc.ucsd.edu.
  163. ^ Rogall, Gail Moede (8 April 2014). "Sea Otters Can Get the Flu, Too". U.S. Department of the Interior, U.S. Geological Survey. Retrieved 11 April 2014.
  164. ^ Silverstein, p. 35
  165. ^ James R Gibson (1969) Feeding the Russian Fur Trade. University of Wisconsin Press. p. 17. ISBN 0299052338
  166. ^ Brass E. (1911) Aus dem Reiche der Pelze, Bd III, Berlin
  167. ^ a b Silverstein, p. 37
  168. ^ Gedney, Larry (6 May 1983). . Archived from the original on 10 June 2007. Retrieved 23 February 2008.
  169. ^ Middleton, p. 8
  170. ^ a b Silverstein, p. 38
  171. ^ Farris, Glenn (2007). "Mains'l Haul, a Journal of Pacific Maritime History, Vol 43". Mains'l Haul. San Diego, California: Maritime Museum of San Diego: 21. ISSN 1540-3386.
  172. ^ Mathes, Michael (2008). The Russian-Mexican Frontier. Jenner, California: Fort Ross Interpretive Association, Inc. p. 326. ISBN 978-1-60643-951-7.
  173. ^ Middleton, p. 4
  174. ^ Silverstein, p. 40
  175. ^ VanBlaricom, p. 50
  176. ^ VanBlaricom, p. 53
  177. ^ VanBlaricom, p. 65
  178. ^ Weise, Elizabeth (31 January 2007). "Damage of Exxon Valdez endures". USA Today. Associated Press. Retrieved 25 December 2001.
  179. ^ Nickerson, pp. 47–48
  180. ^ a b "Aleutian Sea Otter population falls 70% in eight years". CNN. 6 July 2000. Retrieved 4 December 2007.
  181. ^ a b "Sea Otters: Species Description". Alaska SeaLife Center. Retrieved 15 January 2007.
  182. ^ Steve Rubenstein (2 October 2017). "Sea otter census finds 3% decline". San Francisco Chronicle. p. C1.
  183. ^ a b c Kreuder C; Miller MA; Jessup DA; et al. (July 2003). "Patterns of mortality in southern sea otters (Enhydra lutris nereis) from 1998–2001". Journal of Wildlife Diseases. 39 (3): 495–509. doi:10.7589/0090-3558-39.3.495. PMID 14567210. S2CID 8595917.
  184. ^ . NOAA magazine. National Oceanic and Atmospheric Administration. 21 January 2003. Archived from the original on 25 December 2007. Retrieved 24 November 2007.
  185. ^ "National Marine Sanctuaries Regulations". NOAA. Retrieved 19 March 2008.
  186. ^ . City of Monterey. Archived from the original on 11 January 2008. Retrieved 19 March 2008.
  187. ^ "Olympic Coast National Marine Sanctuary History". NOAA. Retrieved 19 March 2008.
  188. ^ a b c VanBlaricom, p. 34
  189. ^ a b Love, pp. 93–98
  190. ^ a b c Silverstein, p. 49
  191. ^ Nickerson, p. 70
  192. ^ a b Falk-Petersen, Jannike; Renaud, Paul; Anisimova, Natalia (12 January 2011). "Establishment and ecosystem effects of the alien invasive red king crab (Paralithodes camtschaticus) in the Barents Sea–a review". ICES Journal of Marine Science. International Council for the Exploration of the Sea (OUP). 68 (3): 479–488. doi:10.1093/icesjms/fsq192. ISSN 1095-9289.
  193. ^ Lyapunova, R.G. (1963) "Museum materials on the Aleuts". Catalog of the Museum of Anthropology and Ethnography. Academy of Sciences, USSR, vol. XXI.
  194. ^ Szpak, Paul; Orchard, Trevor J.; McKechnie, Iain; Gröcke, Darren R. (2012). "Historical Ecology of Late Holocene Sea Otters (Enhydra lutris) from Northern British Columbia: Isotopic and Zooarchaeological Perspectives". Journal of Archaeological Science. 39 (5): 1553–1571. doi:10.1016/j.jas.2011.12.006.
  195. ^ Love, pp 34–35
  196. ^ Chamberlain, B. (1888). Aino Folk Tales. London: The folk-lore society, private printing.
  197. ^ Golder, F. A. (1905). "Aleutian Stories". The Journal of American Folklore. 18 (70): 215–222. doi:10.2307/533140. JSTOR 533140.
  198. ^ Barabash-Nikiforov, N. I. (1947) Калан (Enhydra lutris L.) его биология и вопросы хозяйства (The sea otter (Engydra lutris L): biology and management), Published by: Natural Preservation Ministry of the RSFSR, Moscow.
  199. ^ Hatch, David R. (2002) Elakha: Sea Otters, Native People, and European Colonization in the North Pacific. In Changing Landscapes: Proceedings of the 5th and 6th Annual Coquille Cultural Preservation Conferences. Donald B. Ivy and R. Scott Byram, eds. pp. 79–88. North Bend, OR: Coquille Indian Tribe.
  200. ^ Love, p. 97
  201. ^ VanBlaricom p. 69
  202. ^ . Business Wire. 19 April 2000. Archived from the original on 19 June 2009. Retrieved 9 March 2007.
  203. ^ cynthiaholmes (19 March 2007). "Otters holding hands". Archived from the original on 14 November 2021. Retrieved 24 March 2008 – via YouTube.
  204. ^ "Vancouver sea otters a hit on YouTube". CBC News. 3 April 2007. Retrieved 15 January 2007.
  205. ^ . Vancouver Aquarium. 23 September 2008. Archived from the original on 20 November 2008. Retrieved 28 October 2008.
  206. ^ "Beloved sea otter Milo". Vancouver Aquarium. 12 January 2012. Retrieved 26 November 2014.
  207. ^ https://www.sciencedirect.com/science/article/pii/B9780128014028000044. {{cite web}}: Missing or empty |title= (help)
  208. ^ https://www.sciencedirect.com/science/article/pii/B9780128014028000044. {{cite web}}: Missing or empty |title= (help)

Cited works

  • Kenyon, Karl W. (1969). The Sea Otter in the Eastern Pacific Ocean. Washington, D.C.: U.S. Bureau of Sport Fisheries and Wildlife. ISBN 978-0-486-21346-0.
  • Love, John A. (1992). Sea Otters. Golden, Colorado: Fulcrum Publishing. ISBN 978-1-55591-123-2. OCLC 25747993.
  • Nickerson, Roy (1989). Sea Otters, a Natural History and Guide. San Francisco, CA: Chronicle Books. ISBN 978-0-87701-567-3. OCLC 18414247.
  • Silverstein, Alvin; Silverstein, Virginia and Robert (1995). The Sea Otter. Brookfield, Connecticut: The Millbrook Press, Inc. ISBN 978-1-56294-418-6. OCLC 30436543.
  • Middleton, John (2001). Maritime Activities And Their Perception Today. California Academy of Science's Member Newsletter October/November 2001. San Francisco, California: California Academy of Science. ISSN 1531-2224.
  • VanBlaricom, Glenn R. (2001). Sea Otters. Stillwater, MN: Voyageur Press Inc. ISBN 978-0-89658-562-1. OCLC 46393741.
  • McLeish, Todd (2018). Return of the Sea Otter: The Story of the Animal That Evaded Extinction on the Pacific Coast. Seattle, WA: Sasquatch Books. ISBN 978-1632171375.

External links

 
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Wikispecies has information related to Enhydra lutris.

January 31, 2023
otter, confused, with, marine, otter, eurasian, otter, other, uses, disambiguation, otter, enhydra, lutris, marine, mammal, native, coasts, northern, eastern, north, pacific, ocean, adult, otters, typically, weigh, between, making, them, heaviest, members, wea. Not to be confused with the marine otter or Eurasian otter For other uses see Sea otter disambiguation The sea otter Enhydra lutris 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 and 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 is capable of living exclusively in the ocean Sea otterConservation statusEndangered IUCN 3 1 1 CITES Appendix II CITES 2 note 1 Scientific classificationKingdom AnimaliaPhylum ChordataClass MammaliaOrder CarnivoraFamily MustelidaeSubfamily LutrinaeGenus EnhydraSpecies E lutrisBinomial nameEnhydra lutris Linnaeus 1758 SubspeciesE l lutris E l kenyoni E l nereisSynonymsMustela lutris Linnaeus 1758The sea otter inhabits nearshore environments where it dives to the sea floor to forage It preys mostly on marine invertebrates such as sea urchins various mollusks and crustaceans and some species of fish Its foraging and eating habits are noteworthy in several respects 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 ecosystems 3 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 living in a fraction of their historic range 4 A subsequent international ban on hunting sea otter conservation efforts and reintroduction programs into previously populated areas have contributed to numbers rebounding and the species 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 the sea otter remains classified as an endangered species Contents 1 Evolution 1 1 Taxonomy 1 2 Subspecies 2 Description 3 Behavior 3 1 Foraging 3 2 Social structure 3 3 Reproduction and life cycle 4 Population and distribution 4 1 Japan 4 2 Russia 4 3 British Columbia 4 4 United States 4 4 1 Alaska 4 4 2 Washington 4 4 3 Oregon 4 4 4 California 4 5 Mexico 5 Ecology 5 1 Diet 5 2 As a keystone species 5 3 Predators 6 Relationship with humans 6 1 Fur trade 6 2 Recovery and conservation 6 3 Economic impact 6 4 Roles in human cultures 6 5 Aquariums and zoos 6 6 Current Conservation 7 See also 8 Notes 9 References 9 1 Citations 9 2 Cited works 10 External linksEvolution EditThe sea otter is the heaviest the giant otter is longer but significantly slimmer member of the family Mustelidae 5 a diverse group that includes the 13 otter species and terrestrial animals such as weasels badgers and minks It is unique among the mustelids in not making dens or burrows in having no functional anal scent glands 6 and in being able to live its entire life without leaving the water 7 The only living 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 seals 8 Genetic analysis indicates the sea otter and its closest extant relatives which include the African speckle throated otter European otter African clawless otter and oriental small clawed otter shared an ancestor approximately 5 million years ago 9 Fossil evidence indicates the Enhydra lineage became isolated in the North Pacific approximately 2 million years ago giving rise to the now extinct Enhydra macrodonta and the modern sea otter Enhydra lutris 10 One related species has been described Enhydra reevei from the Pleistocene of East Anglia 11 The modern 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 12 In comparison to cetaceans sirenians and pinnipeds which entered the water approximately 50 40 and 20 million years ago respectively the sea otter is a relative newcomer to a marine existence 13 In some respects though the sea otter is more fully adapted to water than pinnipeds which must haul out on land or ice to give birth 14 The full genome of the northern sea otter Enhydra lutris kenyoni was sequenced in 2017 and may allow for examination of the sea otter s evolutionary divergence from terrestrial mustelids 15 Taxonomy Edit Lutrinae Pteronura giant otter Lontra 4 species Enhydra sea otter Hydrictis spotted necked otter Lutra 2 species Aonyx African clawless Amblonyx Asian small clawed Lutrogale smooth coated Cladogram showing relationships between sea otters and other otters 16 17 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 Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae 18 Originally named Lutra marina it underwent numerous name changes before being accepted as Enhydra lutris in 1922 10 The generic name Enhydra derives from the Ancient Greek en en in and hydra ydra water 19 meaning in the water and the Latin word lutris meaning otter 20 It was formerly sometimes referred to as the sea beaver 21 Subspecies Edit Three subspecies of the sea otter are recognized with distinct geographical distributions Enhydra lutris lutris nominate the Asian sea otter ranges from the Kuril Islands north of Japan to Russia s Commander Islands in the western Pacific Ocean In the eastern Pacific Ocean E l kenyoni the northern sea otter is found from Alaska s Aleutian Islands to Oregon and E l nereis the southern sea otter is native to central and southern California 22 The Asian sea otter is the largest subspecies and has a slightly wider skull and shorter nasal bones than both other subspecies Northern sea otters possess longer mandibles lower jaws while southern sea otters have longer rostrums and smaller teeth 23 24 Description Edit A sea otter s thick fur makes its body appear plumper on land than in the water Skull of a sea otter The sea otter is one of the smallest marine mammal species but it is the heaviest mustelid 7 Male sea otters usually weigh 22 to 45 kg 49 to 99 lb and are 1 2 to 1 5 m 3 ft 11 in to 4 ft 11 in in length though specimens up to 54 kg 119 lb have been recorded 25 Females are smaller weighing 14 to 33 kg 31 to 73 lb and measuring 1 0 to 1 4 m 3 ft 3 in to 4 ft 7 in in length 26 For its size the male otter s baculum is very large massive and bent upwards measuring 150 mm 5 7 8 in in length and 15 mm 9 16 in at the base 27 Unlike most other marine mammals the sea otter has no blubber and relies on its exceptionally thick fur to keep warm 28 With up to 150 000 strands of hair per square centimetre 970 000 in2 its fur is the densest of any animal 29 The fur consists of long waterproof guard hairs and short underfur the guard hairs keep the dense underfur layer dry 26 There is an air compartment between the thick fur and the skin where air is trapped and heated by the body 30 Cold water is kept completely away from the skin and heat loss is limited 26 However a potential disadvantage of this form of insulation is compression of the air layer as the otter dives thereby reducing the insulating quality of fur at depth when the animal forages 30 The fur is thick year round as it is shed and replaced gradually rather than in a distinct molting season 31 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 32 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 33 In adults the head throat and chest are lighter in color than the rest of the body 33 The sea otter displays numerous adaptations to its marine environment The nostrils and small ears can close 34 The hind feet which provide most of its propulsion in swimming are long broadly flattened and fully webbed 35 The fifth digit on each hind foot is longest facilitating swimming while on its back but making walking difficult 36 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 37 The bones show osteosclerosis increasing their density to reduce buoyancy 38 The sea otter presents an insight into the evolutionary process of the mammalian invasion of the aquatic environment which has occurred numerous times over the course of mammalian evolution 39 Having only returned to the sea about 3 million years ago 40 sea otters represent a snapshot at the earliest point of the transition from fur to blubber In sea otters fur is still advantageous given their small nature and division of lifetime between the aquatic and terrestrial environments 41 However as sea otters evolve and adapt to spending more and more of their lifetimes in the sea the convergent evolution of blubber suggests that the reliance on fur for insulation would be replaced by a dependency on blubber This is particularly true due to the diving nature of the sea otter as dives become lengthier and deeper the air layer s ability to retain heat or buoyancy decreases 30 while blubber remains efficient at both of those functions 41 Blubber can also additionally serve as an energy source for deep dives 42 which would most likely prove advantageous over fur in the evolutionary future of sea otters Skull illustration The sea otter propels itself underwater by moving the rear end of its body including its tail and hind feet up and down 35 and is capable of speeds of up to 9 kilometres per hour 5 6 mph 5 When underwater its body is long and streamlined with the short forelimbs pressed closely against the chest 43 When at the surface it usually floats on its back and moves by sculling its feet and tail from side to side 44 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 45 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 46 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 36 Long highly sensitive whiskers and front paws help the sea otter find prey by touch when waters are dark or murky 47 Researchers have noted when they approach in plain view sea otters react more rapidly when the wind is blowing towards the animals indicating the sense of smell is more important than sight as a warning sense 48 Other observations indicate the sea otter s sense of sight is useful above and below the water although not as good as that of seals 49 Its hearing is neither particularly acute nor poor 50 An adult s 32 teeth particularly the molars are flattened and rounded for crushing rather than cutting food 51 Seals and sea otters are the only carnivores with two pairs of lower incisor teeth rather than three 52 the adult dental formula is 3 1 3 1 2 1 3 2 53 The teeth and bones are sometimes stained purple as a result of ingesting sea urchins 54 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 to burn the calories necessary to counteract the loss of heat due to the cold water environment 55 56 Its digestive efficiency is estimated at 80 to 85 57 and food is digested and passed in as little as three hours 28 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 kidneys enable it to derive fresh water from sea water and excrete concentrated urine 58 Behavior Edit Sensitive vibrissae and forepaws enable sea otters to find prey like this purple sea urchin using their sense of touch 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 59 Foraging resumes for a few hours in the afternoon and subsides before sunset and a third foraging period may occur around midnight 59 Females with pups appear to be more inclined to feed at night 59 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 60 Sea otters spend much of their 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 casual observers it appears as if the animals are scratching but they are not known to have lice or other parasites in the fur 61 When eating sea otters roll in the water frequently apparently to wash food scraps from their fur 62 Foraging Edit See also Physiology of underwater diving The sea otter hunts in short dives often to the sea floor Although it can hold its breath for up to five minutes 34 its dives typically last about one minute and not more than four 26 It is the only marine animal capable of lifting and turning over rocks which it often does with its front paws when searching for prey 62 The sea otter may also pluck snails and other organisms from kelp and dig deep into underwater mud for clams 62 It is the only marine mammal that catches fish with its forepaws rather than with its teeth 28 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 This pouch also holds a rock unique to the otter that is used to break open shellfish and clams 63 At the surface 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 mussels with their shells whereas large mussel shells may be twisted apart 64 It uses its lower incisor teeth to access the meat in shellfish 65 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 64 The sea otter s use of rocks when hunting and feeding makes it one of the few mammal species to use tools 66 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 26 Releasing an abalone which can cling to rock with a force equal to 4 000 times its own body weight requires multiple dives 26 Social structure Edit Sleeping sea otters holding paws at the Vancouver Aquarium 67 are kept afloat by their naturally high buoyancy 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 68 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 kelp 69 A male sea otter is most likely to mate if he maintains a breeding territory in an area that is also favored by females 70 As autumn is the peak breeding season in most areas males typically defend their territory only from spring to autumn 70 During this time males patrol the boundaries of their territories to exclude other males 70 although actual fighting is rare 68 Adult females move freely between male territories where they outnumber adult males by an average of five to one 70 Males that do not have territories tend to congregate in large male only groups 70 and swim through female areas when searching for a mate 71 The species exhibits a variety of vocal behaviors The cry of a pup is often compared to that of a gull 72 Females coo when they are apparently content males may grunt instead 73 Distressed or frightened adults may whistle hiss or in extreme circumstances scream 72 Although sea otters can be playful and sociable they are not considered to be truly social animals 74 They spend much time alone and each adult can meet its own hunting grooming and defense needs 74 Reproduction and life cycle Edit While mating the male bites the nose of the female often bloodying and scarring it Sea otters are polygynous males have multiple female partners typically those that inhabit their territory If no territory is established they seek out females in estrus When a male sea otter finds a receptive female the two engage in playful and sometimes aggressive behavior They bond for the duration of estrus or 3 days The male holds the female s head or nose with his jaws during copulation Visible scars are often present on females from this behavior 5 75 Births occur year round with peaks between May and June in northern populations and between January and March in southern populations 76 Gestation appears to vary from four to twelve months as the species is capable of delayed implantation followed by four months of pregnancy 76 In California sea otters usually breed every year about twice as often as those in Alaska 77 Birth usually takes place in the water and typically produces a single pup weighing 1 4 to 2 3 kilograms 3 lb 1 oz to 5 lb 1 oz 78 Twins occur in 2 of births however usually only one pup survives 5 At birth the eyes are open ten teeth are visible and the pup has a thick coat of baby fur 79 Mothers have been observed to lick and fluff a newborn for hours after grooming the pup s fur retains so much air the pup floats like a cork and cannot dive 80 The fluffy baby fur is replaced by adult fur after about 13 weeks 18 A mother floats with her pup on her chest Georg Steller wrote They embrace their young with an affection that is scarcely credible 81 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 82 The milk from a sea otter s two abdominal nipples is rich in fat and more similar to the milk of other marine mammals than to that of other mustelids 83 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 63 Juveniles are typically independent at six to eight months but a mother may be forced to abandon a pup if she cannot find enough food for it 84 at the other extreme a pup may nurse until it is almost adult size 78 Pup mortality is high particularly during an individual s first winter by one estimate only 25 of pups survive their first year 84 Pups born to experienced mothers have the highest survival rates 85 Females perform all tasks of feeding and raising offspring and have occasionally been observed caring for orphaned pups 86 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 87 When foraging she leaves her pup floating on the water sometimes wrapped in kelp to keep it from floating away 88 if the pup is not sleeping it cries loudly until she returns 89 Mothers have been known to carry their pups for days after the pups deaths 81 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 90 A captive male sired offspring at age 19 78 In the wild sea otters live to a maximum age of 23 years 26 with lifespans ranging from 10 to 15 years for males and 15 20 years for females 91 Several captive individuals have lived past 20 years and a female at the Seattle Aquarium died at the age of 28 years 92 Sea otters in the wild often develop worn teeth which may account for their apparently shorter lifespans 93 Population and distribution EditSea otters live in coastal waters 15 to 23 metres 49 to 75 ft deep 94 and usually stay within a kilometre 2 3 mi of the shore 95 They are found most often in areas with protection from the most severe ocean winds such as rocky coastlines thick kelp forests and barrier reefs 96 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 97 Their northern range is limited by ice as sea otters can survive amidst drift ice but not land fast ice 98 Individuals generally occupy a home range a few kilometres long and remain there year round 99 The sea otter population is thought to have once been 150 000 to 300 000 21 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 13 colonies Hunting records researched by historian Adele Ogden place the westernmost limit of the hunting grounds off the northern Japanese island of Hokkaido and the easternmost limit off Punta Morro Hermosa about 21 1 2 miles 34 6 km south of Punta Eugenia Baja California s westernmost headland in Mexico 100 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 with reports of recolonizations in Mexico and Japan 101 Population estimates made between 2004 and 2007 give a worldwide total of approximately 107 000 sea otters 18 102 103 104 105 Japan Edit Adele Ogden wrote in The California Sea Otter Trade that sea otter were hunted from Yezo northeastward past the Kuril Group and Kamchatka to the Aleutian Chain 100 Yezo refers to the island of Hokkaido in northern Japan the only confirmed sea otter population in Japanese territory is on the coast surrounding the town of Erimo Hokkaido 1 Russia Edit Currently the most stable and secure part of the sea otter s range is Russia 106 Before the 19th century around 20 000 to 25 000 sea otters lived near the Kuril Islands with more near Kamchatka and the Commander Islands After the years of the Great Hunt the population in these areas currently part of Russia was only 750 102 By 2004 sea otters had repopulated all of their former habitat in these areas with an estimated total population of about 27 000 Of these about 19 000 are at the Kurils 2 000 to 3 500 at Kamchatka and another 5 000 to 5 500 at the Commander Islands 102 Growth has slowed slightly suggesting the numbers are reaching carrying capacity 102 British Columbia Edit Along the North American coast south of Alaska the sea otter s range is discontinuous A remnant population survived off Vancouver Island into the 20th century but it died out despite the 1911 international protection treaty with the last sea otter taken near Kyuquot in 1929 From 1969 to 1972 89 sea otters were flown or shipped from Alaska to the west coast of Vancouver Island This population increased to over 5 600 in 2013 with an estimated annual growth rate of 7 2 and their range on the island s west coast extended north to Cape Scott and across the Queen Charlotte Strait to the Broughton Archipelago and south to Clayoquot Sound and Tofino 107 108 In 1989 a separate colony was discovered in the central British Columbia coast It is not known if this colony which numbered about 300 animals in 2004 was founded by transplanted otters or was a remnant population that had gone undetected 104 By 2013 this population exceeded 1 100 individuals was increasing at an estimated 12 6 annual rate and its range included Aristazabal Island and Milbanke Sound south to Calvert Island 107 In 2008 Canada determined the status of sea otters to be special concern 109 110 United States Edit Alaska Edit Alaska is the central area of the sea otter s range In 1973 the population in Alaska was estimated at between 100 000 and 125 000 animals 111 By 2006 though the Alaska population had fallen to an estimated 73 000 animals 103 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 112 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 62 Washington Edit In 1969 and 1970 59 sea otters were translocated from Amchitka Island to Washington and released near La Push and Point Grenville The translocated population is estimated to have declined to between 10 and 43 individuals before increasing reaching 208 individuals in 1989 As of 2017 the population was estimated at over 2 000 individuals and their range extends from Point Grenville in the south to Cape Flattery in the north and east to Pillar Point along the Strait of Juan de Fuca 18 In Washington sea otters are found almost exclusively on the outer coasts They can swim as close as six 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 North American river otters which are commonly seen along the seashore However biologists have confirmed isolated sightings of sea otters in these areas since the mid 1990s 18 Oregon Edit 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 113 In 2004 a 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 114 On 18 February 2009 a male sea otter was spotted in Depoe Bay off the Oregon Coast It could have traveled to the state from either California or Washington 115 California Edit California s remote areas of coastline sheltered small colonies of sea otters through the fur trade The 50 that survived in California which were rediscovered in 1938 have since reproduced to almost 3 000 The historic population of California sea otters was estimated at 16 000 before the fur trade decimated the population leading to their assumed extinction Today s population of California sea otters are the descendants of a single colony of about 50 sea otters located near Bixby Creek Bridge in March 1938 by Howard G Sharpe owner of the nearby Rainbow Lodge on Bixby Bridge in Big Sur 116 117 118 Their principal range has gradually expanded and extends from Pigeon Point in San Mateo County to Santa Barbara County 119 Sea otters were once numerous in San Francisco Bay 120 121 Historical records revealed the Russian American Company sneaked 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 100 The founder of Fort Ross Ivan Kuskov finding otters 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 122 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 123 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 124 In the late 1980s the USFWS relocated about 140 southern 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 majority of the San Nicolas sea otters swam back to the mainland 125 Another group of twenty swam 74 miles 119 km north to San Miguel Island where they were captured and removed 126 By 2005 only 30 sea otters remained at San Nicolas 127 although they were slowly increasing as they thrived on the abundant prey around the island 125 The plan that authorized the translocation program had predicted the carrying capacity would be reached within five to 10 years 128 The spring 2016 count at San Nicolas Island was 104 sea otters continuing a 5 year positive trend of over 12 per year 129 Sea otters were observed twice in Southern California in 2011 once near Laguna Beach and once at Zuniga Point Jetty near San Diego These are the first documented sightings of otters this far south in 30 years 130 When the USFWS implemented the translocation program it also attempted in 1986 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 many translocated otters died and also as it proved impractical to capture the hundreds of otters which ignored regulations and swam into the zone 131 However after engaging in a period of public commentary in 2005 the Fish and Wildlife Service failed to release a formal decision on the issue 127 Then in response to lawsuits filed by the Santa Barbara based Environmental Defense Center and the Otter Project on 19 December 2012 the USFWS declared that the no otter zone experiment was a failure and will protect the otters re colonizing the coast south of Point Conception as threatened species 132 Although abalone fisherman blamed the incursions of sea otters for the decline of abalone commercial abalone fishing in southern California came to an end from overfishing in 1997 years before significant otter moved south of Point Conception In addition white abalone Haliotis sorenseni a species never overlapping with sea otter had declined in numbers 99 by 1996 and became the first marine invertebrate to be federally listed as endangered 133 Although the southern sea otter s range has continuously expanded from the remnant population of about 50 individuals in Big Sur since protection in 1911 from 2007 to 2010 the otter population and its range contracted and since 2010 has made little progress 134 135 As of spring 2010 the northern boundary had moved from about Tunitas Creek to a point 2 kilometres 1 2 mi southeast of Pigeon Point and the southern boundary has moved along the Gaviota Coast from approximately Coal Oil Point to Gaviota State Park 136 A toxin called microcystin produced by a type of cyanobacteria Microcystis seems to be concentrated in the shellfish the otters eat poisoning them Cyanobacteria are found in stagnant water 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 137 138 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 139 Great white sharks do not consume relatively fat poor sea otters but shark bitten carcasses have increased from 8 in the 1980s to 15 in the 1990s and to 30 in 2010 and 2011 140 For southern sea otters to be considered for removal from threatened species listing the U S Fish and Wildlife Service USFWS determined that the population should exceed 3 090 for three consecutive years 134 In response to recovery efforts the population climbed steadily from the mid 20th century through the early 2000s then remained relatively flat from 2005 to 2014 at just under 3 000 There was some contraction from the northern now Pigeon Point and southern limits of the sea otter s range during the end of this period circumstantially related to an increase in lethal shark bites raising concerns that the population had reached a plateau 141 However the population increased markedly from 2015 to 2016 with the United States Geological Survey USGS California sea otter survey 3 year average reaching 3 272 in 2016 the first time it exceeded the threshold for delisting from the Endangered Species Act ESA 129 If populations continued to grow and ESA delisting occurred southern sea otters would still be fully protected by state regulations and the Marine Mammal Protection Act which set higher thresholds for protection at approximately 8 400 individuals 142 However ESA delisting seems unlikely due to a precipitous population decline recorded in the spring 2017 USGS sea otter survey count from the 2016 high of 3 615 individuals to 2 688 a loss of 25 of the California sea otter population 143 Mexico Edit Historian Adele Ogden described sea otters are particularly abundant in Lower California now the Baja California Peninsula where seven bays were main centers The southernmost limit was Punta Morro Hermoso about 21 1 2 miles 34 6 km south of Punta Eugenia in turn a headland at the southwestern end of Sebastian Vizcaino Bay on the west coast of the Baja Peninsula Otter were also taken from San Benito Island Cedros Island and Isla Natividad in the Bay 100 By the early 1900s Baja s sea otters were extirpated by hunting In a 1997 survey small numbers of sea otters including pups were reported by local fishermen but scientists could not confirm these accounts 144 However male and female otters have been confirmed by scientists off shores of the Baja Peninsula in a 2014 study who hypothesize that otter dispersed there beginning in 2005 These sea otters may have dispersed from San Nicolas Island which is 300 kilometres 190 mi away as individuals have been recorded traversing distances of over 800 kilometres 500 mi Genetic analysis of most of these animals were consistent with California i e United States otter origins however one otter had a haplotype not previously reported and could represent a remnant of the original native Mexican otter population 145 Ecology EditDiet Edit High energetic requirements of sea otter metabolism require them to consume at least 20 of their body weight a day 30 Surface swimming and foraging are major factors in their high energy expenditure due to drag on the surface of the water when swimming and the thermal heat loss from the body during deep dives when foraging 146 30 Sea otter muscles are specially adapted to generate heat without physical activity 147 Sea otters consume over 100 prey species 148 In most of its range the sea otter s diet consists almost exclusively of marine benthic invertebrates including sea urchins fat innkeeper worms a variety of bivalves such as clams and mussels abalone other mollusks crustaceans and snails 148 149 Its prey ranges in size from tiny limpets and crabs to giant octopuses 148 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 148 In California they have been noted to ignore Pismo clams smaller than 3 inches 76 mm across 150 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 151 The fish species were usually bottom dwelling and sedentary or sluggish forms such as Hemilepidotus hemilepidotus and family Tetraodontidae 151 However south of Alaska on the North American coast fish are a negligible or extremely minor part of the sea otter s diet 18 152 Contrary to popular depictions sea otters rarely eat starfish and any kelp that is consumed apparently passes through the sea otter s system undigested 153 The individuals within a particular area often differ in their foraging methods and prey types and tend to follow the same patterns as their mothers 154 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 18 Sea otters can thoroughly remove abalone from an area except for specimens in deep rock crevices 155 however they never completely wipe out a prey species from an area 156 A 2007 Californian study demonstrated in areas where food was relatively scarce a wider variety of prey was consumed Surprisingly though the diets of individuals were more specialized in these areas than in areas where food was plentiful 125 As a keystone species Edit Sea otters control herbivore populations ensuring sufficient coverage of kelp in kelp forests Sea otters are a classic example of a keystone species their presence affects the ecosystem more profoundly than their size and numbers would suggest They keep the population of certain benthic sea floor herbivores particularly sea urchins in check 3 Sea urchins graze on the lower stems of kelp causing the kelp to drift away and die 157 Loss of the habitat and nutrients provided by kelp forests leads to profound cascade effects on the marine ecosystem North Pacific areas that do not have sea otters often turn into urchin barrens with abundant sea urchins and no kelp forest 5 Kelp forests are extremely productive ecosystems Kelp forests sequester absorb and capture CO2 from the atmosphere through photosynthesis Sea otters may help mitigate effects of climate change by their cascading trophic influence 158 Reintroduction of sea otters to British Columbia has led to a dramatic improvement in the health of coastal ecosystems 159 and similar changes have been observed as sea otter populations recovered in the Aleutian and Commander Islands and the Big Sur coast of California 160 However some kelp forest ecosystems in California have also thrived without sea otters with sea urchin populations apparently controlled by other factors 160 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 160 Sea otters affect rocky ecosystems that are dominated by mussel beds by removing mussels from rocks This allows space for competing species and increases species diversity 160 Predators Edit Leading mammalian predators of this species include orcas and sea lions and bald eagles may grab pups from the surface of the water Young predators may kill an otter and not eat it 66 On land young sea otters may face attack from bears and coyotes In California great white sharks are their primary predator 161 but there is no evidence that the sharks eat them Urban runoff transporting cat feces into the ocean brings Toxoplasma gondii an obligate parasite of felids which has killed sea otters 162 Parasitic infections of Sarcocystis neurona are also associated with human activity 15 According to the U S Geological Survey and the CDC northern sea otters off Washington have been infected with the H1N1 flu virus and may be a newly identified animal host of influenza viruses 163 Relationship with humans EditFur trade Edit Aleut men in Unalaska in 1896 used waterproof kayak gear and garments to hunt sea otters Sea otters have the thickest fur of any mammal which makes them a common 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 21 In the early 18th century Russians began to hunt sea otters in the Kuril Islands 21 and sold them to the Chinese at Kyakhta 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 he 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 1 000 sea otters and were able to command high prices for the pelts 164 Thus began what is sometimes called the Great Hunt which would continue for another hundred years The Russians found the sea otter far more valuable than the sable skins that had driven and paid for most of their expansion across Siberia If the sea otter pelts brought back by Bering s survivors had been sold at Kyakhta prices they would have paid for one tenth the cost of Bering s expedition 165 Pelt sales in thousands in the London fur market the decline beginning in the 1880s reflects dwindling sea otter populations 166 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 the hunters had introduced 167 disputed discuss The Aleut population was reduced by the Russians own estimate from 20 000 to 2 000 168 By the 1760s the Russians had reached Alaska In 1799 Tsar 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 Aleksander 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 in 1818 the indigenous peoples of Alaska were granted civil rights equivalent to a townsman status in the Russian Empire 169 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 167 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 170 Russian hunting expanded to the south initiated by American ship captains who subcontracted Russian supervisors and Aleut hunters 171 in what are 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 and 1846 172 In 1812 the Russians founded an agricultural settlement at what is now Fort Ross in northern California as their southern headquarters 170 Eventually sea otter populations became so depleted commercial hunting was no longer viable It had stopped in the Aleutian Islands by 1808 as a conservation measure imposed by the Russian American Company Further restrictions were ordered by the company in 1834 173 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 174 Prices rose as the species became rare During the 1880s a pelt brought 105 to 165 in the London market but by 1903 a pelt could be worth as much as 1 125 78 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 175 So few remained perhaps only 1 000 2 000 individuals in the wild that many believed the species would become extinct 18 Recovery and conservation Edit Main article Sea otter conservation In the wake of the March 1989 Exxon Valdez oil spill heavy sheens of oil covered large areas of Prince William Sound During the 20th century sea otter numbers rebounded in about two thirds of their historic range a recovery considered one of the greatest successes in marine conservation 176 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 orcas poaching and conflicts with fisheries sea otters can drown if entangled in fishing gear 1 The hunting of sea otters is no longer legal except for limited harvests by indigenous peoples in the United States 177 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 106 The most significant threat to sea otters is oil spills 66 to which they are particularly vulnerable since they rely on their fur to keep warm When their fur is soaked with oil it loses its ability to retain air and the animals can quickly die from hypothermia 66 The liver kidneys and lungs of sea otters also become damaged after they inhale oil or ingest it when grooming 66 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 178 Describing the public sympathy for sea otters that developed from media coverage of the event a U S Fish and Wildlife Service spokesperson wrote As a playful photogenic innocent bystander the sea otter epitomized the role of victim cute and frolicsome sea otters suddenly in distress oiled frightened and dying in a losing battle with the oil 18 The small geographic ranges of the sea otter populations in California Washington and British Columbia mean a single major spill could be catastrophic for that state or province 18 56 62 Prevention of oil spills and preparation to rescue otters if one happens is a major focus for conservation efforts Increasing the size and range of sea otter populations would also reduce the risk of an oil spill wiping out a population 18 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 179 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 180 The most widely accepted but still controversial hypothesis is that killer whales have been eating the otters The pattern of disappearances is consistent with a rise in predation but there has been no direct evidence of orcas preying on sea otters to any significant extent 112 Another area of concern is California where recovery began to fluctuate or decline in the late 1990s 181 Unusually high mortality rates amongst adult and subadult otters particularly females have been reported 105 In 2017 the US Geological Survey found a 3 drop in the sea otter population of the California coast This number still keeps them on track for removal from the endangered species list although just barely 182 Necropsies of dead sea otters indicate diseases particularly Toxoplasma gondii and acanthocephalan parasite infections are major causes of sea otter mortality in California 183 The Toxoplasma gondii parasite which is often fatal to sea otters is carried by wild and domestic cats and may be transmitted by domestic cat droppings flushed into the ocean via sewage systems 183 184 Although disease has clearly contributed to the deaths of many of California s sea otters it is not known why the California population is apparently more affected by disease than populations in other areas 183 Sea otters off the coast of Washington within the Olympic Coast National Marine Sanctuary 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 185 An estimated 1 200 sea otters live within the Monterey Bay National Marine Sanctuary and more than 500 live within the Olympic Coast National Marine Sanctuary 186 187 Economic impact Edit Some of the sea otter s preferred prey species particularly abalone clams and crabs 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 188 The debate is complicated because sea otters have sometimes been held responsible for declines of shellfish stocks that were more likely caused by overfishing disease pollution and seismic activity 62 189 Shellfish declines have also occurred in many parts of the North American Pacific coast that do not have sea otters and conservationists sometimes note 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 189 Although many factors affect shellfish stocks sea otter predation can deplete a fishery to the point where it is no longer commercially viable 188 Scientists agree that sea otters and abalone fisheries cannot exist in the same area 188 and the same is likely true for certain other types of shellfish as well 180 Many facets of the interaction between sea otters and the human economy 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 190 Although human divers harvest red sea urchins both for food and to protect the kelp sea otters hunt more sea urchin species and are more consistently effective in controlling these populations 191 E lutris is a controlling predator of the red king crab Paralithodes camtschaticus in the Bering Sea which would otherwise be out of control as it is in its invasive range the Barents Sea 192 Berents otters Lutra lutra occupy the same ecological niche and so are believed to help to control them in the Berents but this has not been studied 192 The health of the kelp forest ecosystem is significant in nurturing populations of fish including commercially important fish species 190 In some areas sea otters are popular tourist attractions bringing visitors to local hotels restaurants and sea otter watching expeditions 190 Roles in human cultures Edit 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 Peter the Great Museum of Anthropology and Ethnography in St Petersburg Articles depicting sea otters were considered to have magical properties 193 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 the Haida of Haida Gwaii 194 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 potlatches to mark coming of age ceremonies weddings and funerals 67 The Aleuts carved sea otter bones for use as ornaments and in games and used powdered sea otter baculum as a medicine for fever 195 Among the Ainu the otter is portrayed as an occasional messenger between humans and the creator 196 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 197 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 198 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 199 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 181 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 200 Aquariums and zoos Edit Sea otters can do well in captivity and are featured in over 40 public aquariums and zoos 201 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 202 In 2007 a YouTube video of two sea otters holding paws drew 1 5 million viewers in two weeks and had over 22 million views as of July 2022 update 203 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 204 Nyac died in September 2008 at the age of 20 205 Milo the darker one died of lymphoma in January 2012 206 Current Conservation Edit Sea otters being a known keystone species need a humanitarian effort to be protected from endangerment through unregulated human exploitation 207 This species has increasingly been impacted by the large oil spills and environmental degradation caused by overfishing and entanglement in fishing gear 208 Current efforts have been made in legislation the international Fur Seal Treaty The Endangered Species Act IUCN The World Conservation Union Convention on international Trade in Endangered Species of Wild Fauna and Flora Marine Mammal Protection Act of 1972 Other conservation efforts are done through reintroduction and zoological parks International Fur Seal Treaty The Endangered Species Act IUCN The World Conservation Union Convention on international Trade in Endangered Species of Wild Fauna and Flora Marine Mammal Protection Act of 1972 See also EditCalifornia Fur RushNotes Edit Enhydra lutris nereis is included in Appendix IReferences EditCitations Edit a b c Doroff A Burdin A 2015 Enhydra lutris IUCN Red List of Threatened Species 2015 e T7750A21939518 doi 10 2305 IUCN UK 2015 2 RLTS T7750A21939518 en Retrieved 11 November 2021 Appendices CITES cites org Retrieved 14 January 2022 a b Womble Jamie 29 July 2016 A Keystone Species the Sea Otter Colonizes Glacier Bay National Park Service Retrieved 23 November 2021 Riedman M L Estes James A 1990 The sea otter Enhydra lutris behavior ecology and natural history U S Fish and Wildlife Service Biological Report Report Washington D C p 126 Retrieved 27 September 2010 a b c d e Enhydra lutris Animal Diversity Web University of Michigan Museum of Zoology Retrieved 24 November 2007 Kenyon p 4 a b VanBlaricom p 11 Koepfli K P Wayne R K December 1998 Phylogenetic relationships of otters Carnivora Mustelidae based on mitochondrial cytochrome b sequences Journal of Zoology 246 4 401 416 doi 10 1111 j 1469 7998 1998 tb00172 x Koepfli KP Deere KA Slater GJ et al 2008 Multigene phylogeny of the Mustelidae resolving relationships tempo and biogeographic history of a mammalian adaptive radiation BMC Biology 6 10 doi 10 1186 1741 7007 6 10 PMC 2276185 PMID 18275614 a b Love p 9 Willemsen GF 1992 A revision of the Pliocene and Quaternary Lutrinae from Europe Scripta Geologica 101 1 115 CiteSeerX 10 1 1 738 4492 Love pp 15 16 Love pp 4 6 Love p 6 a b Jones Samantha J Haulena Martin Taylor Gregory A Chan Simon Bilobram Steven Warren Rene L Hammond Austin Mungall Karen L Choo Caleb et al 11 December 2017 The Genome of the Northern Sea Otter Enhydra lutris kenyoni Genes 8 12 379 doi 10 3390 genes8120379 PMC 5748697 PMID 29232880 Koepfli KP Deere KA Slater GJ et al 2008 Multigene phylogeny of the Mustelidae Resolving relationships tempo and biogeographic history of a mammalian adaptive radiation BMC Biol 6 4 5 doi 10 1186 1741 7007 6 10 PMC 2276185 PMID 18275614 Bininda Emonds OR Gittleman JL Purvis A 1999 Building large trees by combining phylogenetic information a complete phylogeny of the extant Carnivora Mammalia PDF Biol Rev Camb Philos Soc 74 2 143 75 CiteSeerX 10 1 1 328 7194 doi 10 1017 S0006323199005307 PMID 10396181 a b c d e f g h i j k Washington State Periodic Status Review for the Sea Otter PDF Washington Department of Fish and Wildlife link WDFW seaotter Archived from the original PDF on 10 July 2018 Retrieved 10 July 2018 Liddell Henry George and Robert Scott 1980 A Greek English Lexicon Abridged ed United Kingdom Oxford University Press ISBN 978 0 19 910207 5 OCLC 17396377 Nickerson p 19 a b c d Silverstein p 34 Campbell Kristin M Santana Sharlene E 3 October 2017 Do differences in skull morphology and bite performance explain dietary specialization in sea otters PDF Journal of Mammalogy 98 1408 doi 10 1093 jmammal gyx091 S2CID 91055290 via Oxford University Press Wilson Don E Bogan Michael A Brownell Robert L Burdin A M Maminov M K 13 February 1991 Geographic Variation in Sea Otters Enhydra lutris Journal of Mammalogy 72 1 22 36 doi 10 2307 1381977 JSTOR 1381977 via University of Nebraska Lincoln Timm Davis Lori L DeWitt Thomas J Marshall Christopher D 9 December 2015 Divergent Skull Morphology Supports Two Trophic Specializations in Otters Lutrinae PLOS ONE 10 12 7 Bibcode 2015PLoSO 1043236T doi 10 1371 journal pone 0143236 PMC 4674116 PMID 26649575 The Wildlife Year The Reader s Digest Association Inc 1991 ISBN 0 276 42012 8 a b c d e f g Sea Otters Enhydra lutris MarineBio org 18 May 2017 Retrieved 30 August 2020 Heptner V G Sludskii A A 2002 Mammals of the Soviet Union Vol II part 1b Carnivores Mustelidae and Procyonidae Washington D C Smithsonian Institution Libraries and National Science Foundation p 1342 ISBN 978 90 04 08876 4 a b c Nickerson p 21 Silverstein p 14 a b c d e Yeates Laura 2007 Diving and foraging energetics of the smallest marine mammal the sea otter Enhydra lutris Journal of Experimental Biology 210 Pt 11 1960 1970 doi 10 1242 jeb 02767 PMID 17515421 S2CID 21944946 Kenyon pp 37 39 Love p 21 and 28 a b Love p 27 a b Silverstein p 13 a b Love p 21 a b Kenyon p 70 Silverstein p 11 Hayashi S Houssaye A Nakajima Y Chiba K Ando T Sawamura H Inuzuka N Kaneko N Osaki T 2013 Bone Inner Structure Suggests Increasing Aquatic Adaptations in Desmostylia Mammalia Afrotheria PLOS ONE 8 4 e59146 Bibcode 2013PLoSO 859146H doi 10 1371 journal pone 0059146 PMC 3615000 PMID 23565143 Yuan Yuan Zhang Yaolei Zhang Peijun Liu Chang Wang Jiahao Gao Haiyu Hoelzel A Rus Seim Inge Lv Meiqi Lin Mingli Dong Lijun Gao Haoyang Yang Zixin Caruso Francesco Lin Wenzhi 14 September 2021 Comparative genomics provides insights into the aquatic adaptations of mammals Proceedings of the National Academy of Sciences 118 37 e2106080118 Bibcode 2021PNAS 11806080Y doi 10 1073 pnas 2106080118 ISSN 0027 8424 PMC 8449357 PMID 34503999 Liwanag Heather December 2012 Morphological and thermal properties of mammalian insulation the evolutionary transition to blubber in pinnipeds Biological Journal of the Linnean Society 107 4 774 787 doi 10 1111 j 1095 8312 2012 01992 x a b Liwanag Heather 2008 Fur versus Blubber A comparative look at marine mammal insulation and its metabolic and behavioral consequences Thesis at Cal Poly State University Koopman Heather N 7 March 2018 Function and evolution of specialized endogenous lipids in toothed whales The Journal of Experimental Biology 221 Pt Suppl 1 jeb161471 doi 10 1242 jeb 161471 ISSN 1477 9145 PMID 29514890 S2CID 3789040 Kenyon p 62 Love p 22 VanBlaricom p 64 USFWS Species Profile Southern sea otter Enhydra lutris nereis Archived from the original on 8 December 2008 Retrieved 23 February 2008 VanBlaricom p 11 and 21 Kenyon p 55 Love p 23 Kenyon p 56 Kenyon p 43 Love p 74 Kenyon p 47 Winer J N Liong S M Verstraete F J M 2013 The Dental Pathology of Southern Sea Otters Enhydra lutris nereis Journal of Comparative Pathology 149 2 3 346 355 doi 10 1016 j jcpa 2012 11 243 PMID 23348015 VanBlaricom p 17 a b Sea Otter PDF British Columbia Ministry of Environment Lands and Parks October 1993 Archived from the original PDF on 16 February 2008 Retrieved 13 December 2007 Love p 24 Ortiz RM June 2001 Osmoregulation in marine mammals The Journal of Experimental Biology 204 11 1831 44 doi 10 1242 jeb 204 11 1831 PMID 11441026 a b c Love pp 69 70 Love pp 70 71 Kenyon p 76 a b c d e f Reitherman Bruce 1993 Waddlers and Paddlers A Sea Otter Story Warm Hearts amp Cold Water Documentary U S A PBS a b Haley D ed 1986 Sea Otter Marine Mammals of Eastern North Pacific and Arctic Waters 2nd ed Seattle Washington Pacific Search Press ISBN 978 0 931397 14 1 OCLC 13760343 a b VanBlaricom p 22 Sea otter BBC Retrieved 31 December 2007 a b c d e Sea otter AquaFact file Vancouver Aquarium Marine Science Centre Retrieved 5 December 2007 a b Okerlund Lana 4 October 2007 Too Many Sea Otters Retrieved 15 January 2007 a b Love p 49 VanBlaricom p 45 a b c d e VanBlaricom pp 42 45 Love p 50 a b Kenyon p 77 Kenyon pp 78 79 a b Silverstein p 61 At least one female is known to have died from an infected nose Love p 52 a b Love p 54 Silverstein p 30 a b c d Nowak Roland M 1991 Walker s Mammals of the World Volume II Fifth ed Baltimore and London The Johns Hopkins University Press pp 1141 1143 ISBN 978 0 8018 3970 2 Kenyon p 44 Love pp 56 61 a b Love p 58 Silverstein pp 31 32 Love p 61 a b Love p 63 Love p 62 Love p 59 Kenyon p 89 Silverstein p 31 Silverstein p 28 Love p 53 VanBlaricom p 71 VanBlaricom pp 40 41 VanBlaricom p 41 Silverstein p 17 Nickerson p 49 Silverstein p 19 VanBlaricom p 14 Kenyon p 133 Love pp 67 69 a b c d Ogden Adele 1975 The California sea otter trade 1784 1848 Berkeley California University of California Press p 54 ISBN 978 0 520 02806 7 VanBlaricom p 54 a b c d Kornev S I Korneva S M 2004 Population dynamics and present status of sea otters Enhydra lutris of the Kuril Islands and southern Kamchatka Marine Mammals of the Holarctic Proceedings of 2004 conference pp 273 278 a b Sea Otters Southwest Alaska Sea Otter Recovery Team SWAKSORT U S Fish and Wildlife Service Alaska Archived from the original on 6 February 2008 Retrieved 15 January 2008 a b Barrett Lennard Lance 20 October 2004 British Columbia Sea Otter Research Expedition Vancouver Aquarium Archived from the original on 17 September 2006 Retrieved 11 December 2007 a b Leff Lisa 15 June 2007 California otters rebound but remain at risk Associated Press Archived from the original on 8 January 2011 Retrieved 25 December 2007 a b VanBlaricom p 62 a b Trends in the Abundance and Distribution of Sea Otters Enhydra lutris in British Columbia Updated with 2013 Survey Results PDF Department of Fisheries and Oceans Canada July 2015 Retrieved 10 July 2018 Sea Otter Recovery on Vancouver Island s West Coast Bamfield Marine Sciences Centre Public Education Programme Retrieved 22 August 2011 Sea Otter Species at Risk Public Registry Sea Otters Fisheries and Oceans Canada Nickerson p 46 a b Schrope M February 2007 Food chains killer in the kelp Nature 445 7129 703 5 Bibcode 2007Natur 445 703S doi 10 1038 445703a PMID 17301765 S2CID 4421362 Jameson Ronald James 1975 An Evaluation of Attempts to Reestablish the Sea Otter in Oregon PDF MSc Oregon State University OCLC 9653603 Archived from the original PDF on 25 May 2017 Retrieved 30 December 2009 Quinn Beth 17 October 2004 Sea otter s stay raises scientists hopes PDF The Oregonian Archived from the original PDF on 30 December 2010 Retrieved 30 December 2009 Rare sea otter confirmed at Depoe Bay The Oregonian 20 February 2009 Retrieved 27 February 2009 Williams Honey Redwood Sanctuary PDF Retrieved 18 December 2017 Hathaway Pat Bixby Creek Bridge on Highway One from the Pat Hathaway Photo Collection caviews com Retrieved 18 December 2017 Silverstein p 41 Spring 2007 Mainland California Sea Otter Survey Results U S Geological Survey 30 May 2007 Retrieved 23 February 2008 Rogers Paul 11 December 2020 Are sea otters taking a bite out of California s Dungeness crab season The Mercury News Retrieved 12 December 2020 Southern Sea Otters Archived 30 November 2011 at the Wayback Machine nrdc org Bancroft Hubert Howe Bates Alfred Petroff Ivan Nemos William 1887 History of Alaska 1730 1885 San Francisco California A L Bancroft amp Company p 482 Retrieved 26 September 2010 Stewart Suzanne Praetzellis Adrian November 2003 Archeological Research Issues for the Point Reyes National Seashore Golden Gate National Recreation Area PDF Report Anthropological Studies Center Sonoma State University p 335 Retrieved 26 September 2010 Battersby Bob Maginis Preston Nielsen Susan Scales Gary Torney Richard Wynne Ed May 2008 Ross California The people the places the history Ross Historical Society Retrieved 3 November 2010 a b c University of California Santa Cruz 18 January 2008 Sea Otter Show Striking Variability in Diets And Feeding Strategies ScienceDaily Retrieved 20 January 2008 mcLeish p 32 a b U S Fish and Wildlife Service Proposes that Southern Sea Otter Translocation Program be Terminated PDF U S Fish and Wildlife Service 5 October 2005 Retrieved 10 April 2008 Service Proposes to End Southern Sea Otter Translocation Program USFWS Pacific Southwest Region 17 August 2011 Retrieved 21 December 2012 a b Hatfield B B Tinker M T 19 September 2016 Annual California Sea Otter Census 2016 Spring Census Summary USGS Western Ecological Research Center Report doi 10 5066 F7FJ2DWJ Rare sighting of sea otter off Laguna Beach KABC TV DT 7 December 2011 Archived from the original on 21 October 2013 Retrieved 8 December 2011 Balance sought in sea otter conflict CNN 24 March 1999 Retrieved 25 January 2008 Weiss Kenneth R 20 December 2012 U S will let otters roam along Southern California coastline Los Angeles Times Retrieved 21 December 2012 mcLeish p 264 a b California s Sea Otter Numbers Continue Slow Climb USGS 12 September 2013 Retrieved 20 October 2013 Young Landis Ben Tinker Tim Hatfield Brian 3 August 2010 California Sea Otter Numbers Drop Again U S Geological Survey Retrieved 23 January 2011 Spring 2010 Mainland California Sea Otter Survey Results USGS Western Ecological Research Center Retrieved 26 September 2010 Weiss Kenneth R 23 September 2010 Another deadly challenge for the sea otter Los Angeles Times Retrieved 10 November 2010 Miller MA Kudela RM Mekebri A Crane D Oates SC et al 2010 Thompson Ross ed Evidence for a Novel Marine Harmful Algal Bloom Cyanotoxin Microcystin Transfer from Land to Sea Otters PLOS ONE 5 9 e12576 Bibcode 2010PLoSO 512576M doi 10 1371 journal pone 0012576 PMC 2936937 PMID 20844747 Colliver Victoria 23 January 2011 Sea otter deaths jump in 2010 San Francisco Chronicle Retrieved 23 January 2011 USGS April 2012 Number of dead California sea otters a record high in 2011 Marine Pollution Bulletin 64 4 671 674 doi 10 1016 j marpolbul 2012 03 002 Hatfield Brian Tinker Tim 22 September 2014 Spring 2014 California Sea Otter Census Results Report Retrieved 6 December 2015 Southern Sea Otter USFWS Ventura Fish and Wildlife Office Retrieved 28 December 2016 Tinker M T Hatfield B B 29 September 2017 California sea otter Enhydra lutris nereis census results Spring 2017 California sea otter Enhydra lutris nereis census results spring 2017 Report Data Series U S Geological Survey Data Series 1067 p 9 doi 10 3133 ds1067 Gallo Reynoso JP Rateibun GB 1997 Status of Sea Otters Enhydra Lutris in Mexico Marine Mammal Science 13 2 332 340 doi 10 1111 j 1748 7692 1997 tb00639 x Schramm Y Heckel G Saenz Arroyo A Lopez Reyes E Baez Flores A Gomez Hernandez G Lazode la Vega Trinker A Lubinsky Jinich D de los Angeles Milanes Salinas M 2014 New evidence for the existence of southern sea otters Enhydra lutris nereis in Baja California Mexico Marine Mammal Science 30 3 1264 1271 doi 10 1111 mms 12104 Williams Terrie 1989 Swimming by sea otters adaptations for low energetic cost locomotion Journal of Comparative Physiology A 164 6 815 824 doi 10 1007 BF00616753 PMID 2724187 S2CID 1926452 Wright Traver Sheffield Moore Melinda Davis Randall 2 December 2021 Sea otters demonstrate that there is more to muscle than just movement it can also bring the heat The Conversation Retrieved 8 December 2021 a b c d VanBlaricom pp 18 29 Elkhorn Slough Mammals Sea Otter elkhornslough org Love p 96 a b Kenyon p 121 Love p 76 Kenyon p 119 VanBlaricom p 29 VanBlaricom p 30 Nickerson p 57 Chrobak Ula 15 September 2021 How sea otters can fight climate change BBC Retrieved 11 December 2021 Sezen Uzay 29 May 2017 Otters vs Climate Change KQED QUEST 2014 Nature Documentaries Retrieved 6 June 2017 Aquatic Species at Risk Species Profile Sea Otter Fisheries and Oceans Canada Archived from the original on 23 November 2007 Retrieved 29 November 2007 a b c d VanBlaricom p 33 Nickerson P Sea Otter Frequently Asked Questions Defenders of Wildlife p 65 Archived from the original on 9 July 2011 Retrieved 31 August 2011 Parasite Shed in Cat Feces Kills Sea Otters California Sea Grant PDF www csgc ucsd edu Rogall Gail Moede 8 April 2014 Sea Otters Can Get the Flu Too U S Department of the Interior U S Geological Survey Retrieved 11 April 2014 Silverstein p 35 James R Gibson 1969 Feeding the Russian Fur Trade University of Wisconsin Press p 17 ISBN 0299052338 Brass E 1911 Aus dem Reiche der Pelze Bd III Berlin a b Silverstein p 37 Gedney Larry 6 May 1983 The Aleut and the Otter Archived from the original on 10 June 2007 Retrieved 23 February 2008 Middleton p 8 a b Silverstein p 38 Farris Glenn 2007 Mains l Haul a Journal of Pacific Maritime History Vol 43 Mains l Haul San Diego California Maritime Museum of San Diego 21 ISSN 1540 3386 Mathes Michael 2008 The Russian Mexican Frontier Jenner California Fort Ross Interpretive Association Inc p 326 ISBN 978 1 60643 951 7 Middleton p 4 Silverstein p 40 VanBlaricom p 50 VanBlaricom p 53 VanBlaricom p 65 Weise Elizabeth 31 January 2007 Damage of Exxon Valdez endures USA Today Associated Press Retrieved 25 December 2001 Nickerson pp 47 48 a b Aleutian Sea Otter population falls 70 in eight years CNN 6 July 2000 Retrieved 4 December 2007 a b Sea Otters Species Description Alaska SeaLife Center Retrieved 15 January 2007 Steve Rubenstein 2 October 2017 Sea otter census finds 3 decline San Francisco Chronicle p C1 a b c Kreuder C Miller MA Jessup DA et al July 2003 Patterns of mortality in southern sea otters Enhydra lutris nereis from 1998 2001 Journal of Wildlife Diseases 39 3 495 509 doi 10 7589 0090 3558 39 3 495 PMID 14567210 S2CID 8595917 Parasite in cats killing sea otters NOAA magazine National Oceanic and Atmospheric Administration 21 January 2003 Archived from the original on 25 December 2007 Retrieved 24 November 2007 National Marine Sanctuaries Regulations NOAA Retrieved 19 March 2008 Monterey Bay National Marine Sanctuary City of Monterey Archived from the original on 11 January 2008 Retrieved 19 March 2008 Olympic Coast National Marine Sanctuary History NOAA Retrieved 19 March 2008 a b c VanBlaricom p 34 a b Love pp 93 98 a b c Silverstein p 49 Nickerson p 70 a b Falk Petersen Jannike Renaud Paul Anisimova Natalia 12 January 2011 Establishment and ecosystem effects of the alien invasive red king crab Paralithodes camtschaticus in the Barents Sea a review ICES Journal of Marine Science International Council for the Exploration of the Sea OUP 68 3 479 488 doi 10 1093 icesjms fsq192 ISSN 1095 9289 Lyapunova R G 1963 Museum materials on the Aleuts Catalog of the Museum of Anthropology and Ethnography Academy of Sciences USSR vol XXI Szpak Paul Orchard Trevor J McKechnie Iain Grocke Darren R 2012 Historical Ecology of Late Holocene Sea Otters Enhydra lutris from Northern British Columbia Isotopic and Zooarchaeological Perspectives Journal of Archaeological Science 39 5 1553 1571 doi 10 1016 j jas 2011 12 006 Love pp 34 35 Chamberlain B 1888 Aino Folk Tales London The folk lore society private printing Golder F A 1905 Aleutian Stories The Journal of American Folklore 18 70 215 222 doi 10 2307 533140 JSTOR 533140 Barabash Nikiforov N I 1947 Kalan Enhydra lutris L ego biologiya i voprosy hozyajstva The sea otter Engydra lutris L biology and management Published by Natural Preservation Ministry of the RSFSR Moscow Hatch David R 2002 Elakha Sea Otters Native People and European Colonization in the North Pacific In Changing Landscapes Proceedings of the 5th and 6th Annual Coquille Cultural Preservation Conferences Donald B Ivy and R Scott Byram eds pp 79 88 North Bend OR Coquille Indian Tribe Love p 97 VanBlaricom p 69 Seattle Aquarium s Youngest Sea Otter Lootas Becomes a Mom Business Wire 19 April 2000 Archived from the original on 19 June 2009 Retrieved 9 March 2007 cynthiaholmes 19 March 2007 Otters holding hands Archived from the original on 14 November 2021 Retrieved 24 March 2008 via YouTube Vancouver sea otters a hit on YouTube CBC News 3 April 2007 Retrieved 15 January 2007 Vancouver Aquarium s oldest sea otter Nyac passes Vancouver Aquarium 23 September 2008 Archived from the original on 20 November 2008 Retrieved 28 October 2008 Beloved sea otter Milo Vancouver Aquarium 12 January 2012 Retrieved 26 November 2014 https www sciencedirect com science article pii B9780128014028000044 a href Template Cite web html title Template Cite web cite web a Missing or empty title help https www sciencedirect com science article pii B9780128014028000044 a href Template Cite web html title Template Cite web cite web a Missing or empty title help Cited works Edit Kenyon Karl W 1969 The Sea Otter in the Eastern Pacific Ocean Washington D C U S Bureau of Sport Fisheries and Wildlife ISBN 978 0 486 21346 0 Love John A 1992 Sea Otters Golden Colorado Fulcrum Publishing ISBN 978 1 55591 123 2 OCLC 25747993 Nickerson Roy 1989 Sea Otters a Natural History and Guide San Francisco CA Chronicle Books ISBN 978 0 87701 567 3 OCLC 18414247 Silverstein Alvin Silverstein Virginia and Robert 1995 The Sea Otter Brookfield Connecticut The Millbrook Press Inc ISBN 978 1 56294 418 6 OCLC 30436543 Middleton John 2001 Maritime Activities And Their Perception Today California Academy of Science s Member Newsletter October November 2001 San Francisco California California Academy of Science ISSN 1531 2224 VanBlaricom Glenn R 2001 Sea Otters Stillwater MN Voyageur Press Inc ISBN 978 0 89658 562 1 OCLC 46393741 McLeish Todd 2018 Return of the Sea Otter The Story of the Animal That Evaded Extinction on the Pacific Coast Seattle WA Sasquatch Books ISBN 978 1632171375 External links Edit Wikimedia Commons has media related to Enhydra lutris Sea otter Wikispecies has information related to Enhydra lutris Enhydra lutris Linnaeus 1758 at the Integrated Taxonomic Information System Enhydra lutris Linnaeus 1758 at the World Register of Marine Species De Bestiis Marinis or The Beasts of the Sea 1751 PDF pp 68 82 transcribed field notes from 18th century German zoologist Georg Wilhelm Steller Precipice of Survival The Southern Sea Otter Archived 22 April 2008 at the Wayback Machine Adobe Flash a 48 minute program on the southern sea otter s history by the United States Geological Survey Portals Marine life Mammals Animals Biology Retrieved from https en wikipedia org w index php title Sea otter amp oldid 1136152597, wikipedia, wiki, book, books, library,

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