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Deepseawaters
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Sea Otters
Deep Sea Otter
Common Name: Sea Otters
Scientific Name: Enhydra lutris
 What
Is Sea Otter?
What
Do Sea Otter Eat?
Where
Do Sea Otter Live?
How
Do Sea Otter Reproduce?
What
Makes Them Unique?
What
Do They Look Like?
What
Is Their Status?
Why
Are Sea Otters At Risk?
What
Can We Do?
What Is
Sea Otter?
 Sea
otters are unusual among marine mammals
in that they live outside of their zone of thermal neutrality
and consequently have extremely high metabolic demands. As
a result they require a high rate of food intake, up to 30%
of their body weight per day, and they have limited capacity
to cope with reduced food availability or additional physiological
challenges. Moreover, a large proportion of their diet consists
of filter-feeding benthic invertebrates, which tend to concentrate
both contaminants and disease-causing pathogens that flow
into near-shore waters from land.
With their elevated metabolic
rates, sea otters must consume large quantities
of these invertebrates and thus they have high exposure rates
to the associated parasites and pollutants. The net result
of all these traits is that sea otters are
especially susceptible to human-induced stressors in their
environment, and like the proverbial “canary in a
coal mine,” they represent effective sentinels of
the health of coastal oceans. Their utility
as a sentinel (or indicator) of ecosystem health is further
increased by their near-shore distribution, their extraordinary
appeal to the general public (a fact that generates community
support for monitoring efforts), and because they are relatively
easy to observe.
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What Do
Sea Otter Eat?
 Sea
Otters dive to the seafloor to obtain a variety of
invertebrate animals. The most common prey of Sea
Otters are sea urchins, mussels,
abalone, clams, scallops, crabs,
sea snails, chitons, octopus, and
squid. An acute sense of touch, using paws, nose,
and whiskers, is very important for finding prey in crevices
or bottom sediments, and during dim light. Food items are
normally clasped between tough leathery pads of the two forepaws
and brought to the surface to eat. Several food items are
often stored in a loose pocket of skin in the armpit area
for transportation and while feeding.
The ingenious Sea Otter
uses rocks as tools to break open hard-shelled prey or to
dislodge prey such as abalone. It is the only mammal other
than the primates (monkeys, apes, humans) known to use tools.
While eating, Sea Otters float on their backs,
using their chest as a dinner table, and are often accompanied
by gulls and small fish which scavenge on leftovers. Items
such as crabs and urchins are broken open with paws
and teeth; the teeth are modified for crushing hard foods.
Hard-shelled mussels and clams are bashed repeatedly against
a stone on the otter's chest. Their rock tools range
from 6 to 15 cm across, and favourite rocks may be carried
in the armpit pouch on several successive dives.
Most foraging is at depths under 30 metres,
but a dive to 100 m has been recorded. Research on the west
coast of Vancouver Island found that food dives varied from
45 to 127 seconds, the longest interval between food dives
was 180 seconds, and individuals may spend up to two hours
diving for one kind of food.
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Where
Do Sea Otter Live?
 Sea Otters need unpolluted
nearshore marine habitats, usually having depths under 40
m, an abundant food supply consisting primarily of shellfish,
and freedom from excessive human disturbance. Complex coastlines
having many islands, reefs, bays, and points provide
a variety of feeding sites and shelter from storms, and appear
to support the highest numbers of otters. Habitats
of this nature occur along most of the outer coast of British
Columbia. The reintroduced British Columbia population, possibly
with the help of animals from northern Washington and southeast
Alaska, may eventually expand their range into this vacant
habitat.
B.C.'s deep, steep-sided fjords may have
little to offer Sea Otters in terms of food,
and provide little protection from strong outflow winds. Georgia
Strait may be unsuitable due to high summer water temperatures,
particularly in its shallow nearshore waters, or because of
pollution and human disturbance.
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How Do
Sea Otter Reproduce?
 Females breed at four years old and have
one pup every one to two years. Males mature at five or six
years but may not breed until somewhat older. Although young
may be born at any time of year, most births occur in spring
or early summer. Most mating in northern waters is in the
fall. The estimated gestation period is 6W to 9 months. Spring
or early summer births may result in better survival than
births at other seasons.
Few births have been seen, but most are thought
to occur in the water (unlike River Otters, seals
and sea lions, which usually give birth on land).
At birth the single pup weighs 1.4 to 2.3 kg and is well furred
but relatively helpless. Pups receive a lot of maternal care
and training until almost adult size, a period of six to eight
months or more. Small pups suckle while lying on the female's
chest; when larger they nurse while lying beside her in the
water. Females with small pups tend to be solitary and to
act aggressively toward other otters.
Females leave pups on the surface when they
dive for food. They share solid food with the pups shortly
after birth, but larger pups aggressively take food from their
mothers. The young begin to dive in their second month; the
duration of dives and success in finding food increases with
age. There is much to learn during the period of dependency.
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What makes
them unique?
 In contrast to whales
and seals, which rely on their blubber for insulation,
the Sea Otter relies on its wellgroomed fur
with many tiny air bubbles trapped in it. They have the thickest
fur of any living animal, with an incredible 100 000 or more
hairs per square centimetre. Frequent grooming activity prevents
soiling of the fur, loss of insulation, and reduced buoyancy.
The fur is rubbed meticulously with front and hind feet, the
flexible otter rolling inside its baggy skin to reach
the awkward parts. Folds of skin are squeezed between the
forepaws or with the tongue to remove moisture. Finally the
fur is aerated by blowing into it or churning the water to
a froth with the paws.
To maintain body heat in chilly north Pacific
waters, Sea Otters have a metabolic rate
two or three times that of land mammals of similar size. This
is made possible by a prodigious food intake (25 to 30 percent
of body weight each day), an intestine 10 times the body length,
and a rapid digestive rate. Air in the fur, together with
large lungs (an adaptation for diving) cause Sea Otters
to float high in the water. Other adaptations for diving include
blood with a very high capacity to transport oxygen, and ear
canals which can be closed. The Sea Otter
has large, complex kidneys which allow it to drink seawater.
Sea Otters walk awkwardly
on land and even in water do not have the speed or agility
of seals. When lying face-up they move slowly by sculling
the tail or paddling with one or both hindlimbs. Faster movements
are always belly-down and involve up and down undulations
of the entire body ("porpoising") with the hindfeet and tail
held stiffly as an extension of the body, and the forefeet
held against the chest. Normal speeds are 1 to 5 km an hour;
the maximum about 9 km an hour. When at rest, Sea
Otters lie on their backs, usually entwined in kelp
to hold their position, feet held high in the air to prevent
heat loss.
Most of a Sea Otter's day
is spent feeding, grooming, or resting, usually in that order.
Otters in Washington and British Columbia, where populations
are small and food is abundant, may spend as little as 10
or 15 percent of their day feeding, compared to 50 or 60 percent
at Amchitka Island, where otter numbers are high and readily
available foods have been exhausted. Most daytime foraging
activity occurs in the morning and late afternoon, most resting
around midday.
The near extinction and subsequent increase
of Sea Otters has allowed researchers to
study their effects on benthic (seabottom)
plant and animal communities as they recolonized
or were transplanted into vacant habitats. Many areas that
were otter-free for decades, particularly rocks and reefs,
have dense populations of sea urchins and little
or no kelp (large algae), this having been eaten
by the grazing urchins. These areas are described as "sea
urchin barrens." Research at Checleset Bay, Vancouver
Island, and elsewhere has shown that introduced Sea Otters
greatly reduce the urchin populations, allowing extensive
stands of kelp to develop. These "kelp forests"
drastically change the reef environment, provide habitat for
fish such as perch, greenling, and lingcod, and moderate the
effect of waves. Their foraging has thus had a profound influence
on nearshore reef communities.
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What Do
They Look Like?
 Two species of otters occur
in British Columbia - the Sea Otter and the more
widespread River Otter. River Otters frequent rivers and lakes,
but are also common in saltwater along the entire British
Columbia coast. An otter in the sea is usually not a Sea Otter!
The Sea Otter (Enhydra lutris)
is our smallest marine mammal, but is one
of the largest of the world's 13 otter species - males weigh
up to 45 kilograms and reach 148 centimetres in length. Females
are slightly smaller. The tail is about one-third the length
of head and body; the River Otter's is about twothirds. Sea
Otters are frequently seen in large social groups, resting
or feeding on their backs in offshore kelp beds.
They rarely go ashore, but when they do, they choose remote
offshore reefs or bars. River Otters seldom occur in groups
larger than a single family (although families can include
three or four young), don't rest on their backs, and come
ashore frequently.
Sea Otter fur, consisting
of sparse guard hairs and dense, soft underfur, varies from
dark brown to reddish brown. When dry, the fur on the head
is cinnamon to light brown. The body is entirely furred except
for the tip of the nose, inside of the ears, and palms of
the stubby mitten-like forefeet. The flipperlike hindfeet
have short, sparse fur. Prominent whiskers, and the grizzled
facial fur of older animals have given rise to the nickname
"old man of the sea."
Groups of the sociable Sea Otter
are called rafts, and usually consist entirely
of females and pups or of males. Male rafts are usually larger
(up to 100 or more in Alaska); but female rafts may contain
up to 40 adults with their pups. Most individuals make short
daily movements between favourite feeding sites and more protected
resting areas, resulting in seasonal home ranges of 5 to 10
square kilometres in size. However, studies in Alaska and
California have shown that many adult males make yearly or
more frequent trips of 80 to 145 km from male rafts to establish
temporary breeding territories in female areas.
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What Is
Their Status?
 Following reintroduction, the Sea
Otter population in Canada has increased to about
900 animals and has been growing at a rate of 17 to 20 percent
per year. The Sea Otter has been assigned Endangered
status by the Committee on the Status of Endangered Wildlife
in Canada (COSEWIC), and receives legal protection as a marine
mammal under the Canada Fisheries Act. It has been placed
on British Columbia's Red List and has been legally designated
as an Endangered Species under the Wildlife Act.
Throughout their range in the U.S., Sea
Otters receive protection under the Marine Mammals
Protection Act. The California population, a separate subspecies
(variety) named the "Southern Sea Otter,"
is afforded additional Federal protection as a Threatened
Species under the U.S. Endangered Species Act.
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Why Are
Sea Otters At Risk?
 Prior to decimation by the fur trade, Sea
Otters were found in a great arc around the North
Pacific: from northern Japan via the coastlines of the Kuril
Islands, Kamchatka, Commander and Aleutian Islands, Gulf of
Alaska, British Columbia, Washington, Oregon and California,
south to the vicinity of Cedros Island, Mexico.
Native people harvested Sea Otters
throughout their range, but this was unlikely to have seriously
reduced any populations. However, a 150-year period of ruthless
exploitation began with Vitus Bering’s exploration of
the Aleutians and Gulf of Alaska in 1741. The journals of
such explorers, and the luxuriant pelts they brought back,
revealed to the world the commercial potential of this far-flung
resource. The ensuing maritime fur trade, with China and Europe
the major markets, resulted in fierce competition between
Russian, American, British, and Spanish traders, and sparked
numerous territorial disputes. One of these, the “Nootka
Controversy,” brought threats of war between Britain
and Spain.
Prior to exploitation, the worldwide population
of Sea Otters was estimated at between 150
000 and 300 000. During 126 years of Russian control, more
than 800 000 are believed to have been taken in Alaska alone.
Hundreds of thousands were also obtained along the Alaska
to California coastline. By 1911, when a treaty to protect
fur seals and Sea Otters was signed by Japan, Russia,
Britain (for Canada) and the United States, between 1000 and
2000 Sea Otters remained in a dozen scattered locations
from the Kuril Islands, Russia, to Prince William Sound, Alaska,
and at one site near Carmel, California. The last Canadian
record was a specimen obtained near Kyuquot on Vancouver Island
in 1929.
Following protection, the remnant Sea
Otter populations increased gradually. An estimated 150
000 or more now occupy most of their original range from the
Kuril Islands to Prince William Sound, and the isolated remnant
in California has increased to about 2000.
Like most marine mammals, Sea Otters
have low reproductive rates. However, many new populations
in formerly vacant habitats have increased steadily at rates
as high as 17 to 20 percent per year, indicating that in areas
where populations have not reached the limits of their habitat,
natural mortality levels must also be quite low. In areas
where populations have reached maximum densities, such as
Amchitka Island in Alaska, starvation is probably the most
common cause of death. Mortality also occurs due to excessively
worn teeth, which may be accompanied by disease, parasitism,
or infection. Severe, prolonged storms can also cause death
of pups, aged, or weak individuals. At Amchitka Island, nesting
Bald Eagles regularly prey on Sea Otter pups left untended
on the ocean surface. This may also happen in other areas.
There are reports of predation by Killer Whales,
sharks and sea lions.
Human-caused mortality, though much reduced
since the early 1900s, is still a cause for concern. The Exxon
Valdez oil spill in Prince William Sound, Alaska, in 1989
wiped out nearly half of the Sea Otters in
the oiled area of the Sound; the much smaller Nestucca spill
off Washington in 1988 killed at least one otter at Checleset
Bay, 440 kilometres north of the spill site. Small amounts
of oil, by affecting insulation, can cause hypothermia for
Sea Otters, and any major spill, an ongoing
threat on the B.C. coast, could be catastrophic. Entanglement
in fishing nets may cause significant losses in some parts
of their range. Shooting, harassment and general disturbance
by boat traffic are of common concern in California where
large numbers of people live in close proximity to these animals.
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What Can
We Do?
 Sea Otters were reintroduced
to Canadian waters between 1969 and 1972. This was a cooperative
effort involving BC Environment (Fish and Wildlife Branch),
Fisheries and Oceans Canada (Pacific Biological Station),
Canadian Armed Forces (Search and Rescue, Comox), U.S. Bureau
of Sport Fisheries and Wildlife, Alaska Fish and Game Department,
and U.S. Atomic Energy Commission. There were three releases
totalling 89 Sea Otters (taken from Amchitka Island
and Prince William Sound) at the Bunsby Islands in Checleset
Bay, on Vancouver Island, during this time. This nucleus has
grown to over 900, distributed from Nootka Sound to Quatsino Sound, and
is increasing.
An Ecological Reserve covering all of Checleset Bay (the
Sea Otter release site) was established by BC Parks in 1981,
and harvest closures on many key shellfish eaten by the otters
(clams, sea urchins, abalone) have been instituted in the
reserve by the Department of Fisheries and Oceans Canada (DFO).
Periodic aerial surveys are undertaken by BC Environment, BC Parks, and DFO.
Two status reports have been prepared and recovery and management
plans are in preparation. BC Parks controls activities in
Checleset Bay by issuing research, educational, and other
permits. Research has been undertaken there on effects of
Sea Otters on marine communities.
Once extinct on our coast, Sea Otters
are now expanding to reoccupy their former habitats and to
resume their role in the ecology of B.C.’s coastal ecosystems.
Expansion to new areas will also provide increased opportunities
for the public to view this engaging animal in the wild. The
outlook for B.C.’s Sea Otter is good, although
present populations are still relatively small and vulnerable.
The public is urged to support programs aimed at preserving
this valuable member of our coastal fauna.
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