Deep Sea Otter
Common Name: Sea Otters
Scientific Name: Enhydra lutris
Is Sea Otter?
Makes Them Unique?
Do Sea Otter Eat?
Do Sea Otter Live?
Do Sea Otter Reproduce?
Do They Look Like?
Is Their Status?
Are Sea Otters At Risk?
Can We Do?
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.
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.
Do Sea Otter Eat?
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.
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
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
Do Sea Otter Live?
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.
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
Do Sea Otter Reproduce?
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.
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.
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.
makes them unique?
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.
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.
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.
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.
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.
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!
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
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."
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.
Is Their Status?
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.
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
Are Sea Otters At Risk?
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.
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.
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.
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.
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
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.
Can We Do?
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.
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.
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.
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.
Back to Top