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Sea Otter Fact File

Enhydra lutris

Weight

15-45kg

(33-99lbs)

Length

1-1.2m

(3.25-4ft)

Lifespan

Wild 20 years

Captive 20 years

Diet

Carnivore

Shellfish, Fish

Conservation Status

IUCN

Endangered

The sea otter is covered by the densest fur of any mammal. Every 1sq cm (0.15sq in) of their skin is covered by as many as 100,000 hairs. This allows them to keep warm as their entire life is spent in the water.

Sea otters can dive under the water for up to 4 minutes at a time to reach fish, mollusk and shellfish to feed on. These are then brought to the surface where they use tools to access the inside.

They make their home along the coastlines of countries bordering the Pacific Ocean.

Sea otters were almost driven to extinction by hunting for their fur. More recently oil spills and climate change have contributed to their decline.

Read on to learn more about these amazing mammals.

Appearance

Sea otters are covered by the densest fur of any mammal. Per 1sq cm (0.15sq in) of skin they may have 100,000 hairs. This is an adaptation which allows them to keep warm while in the ocean. They rely on this adaptation as they lack the thick blubber which most mammals use to keep warm.

The fur is in two layers. The top waterproof guard layer helps to protect the fur underneath and keep it warm.

Across most of the body this fur is colored brown except for the head where their is a straw colored patch of fur.

They have webbed and flipper-shaped hind feet helping to push them through the water. Their front paws are equipped with small claws which are used to hold food. These claws are retractable.

On either side of the face the sea otter has sensitive whiskers which can be used to find food under water.

At the end of the body is a strong, flat tail which acts like a rudder to push them through the water.

Sea otters are the only carnivore which have 4 lower incisors.

An average adult sea otter will measure 1-1.2m (3.25-4ft) and weigh 15-45kg (33-99lbs).

Diet


Sea otters are carnivores and hunt in the water for fish, mollusks and shellfish. They tend to favor larger sized pray items.

When foraging for food they will dive for a minute or two to collect food and then come to the surface and turn on their backs to eat.

Feeding on sea urchins helps to keep the kelp forest healthy which is their primary habitat.

These animals have been recorded to use tools when feeding. They will smash the hard shells of their food against stones to be able to access the soft meat inside. This process is undertaken while at the water's surface.

When foraging they can store food in loose skin folds under the forearm which then leaves their hands free so they can hunt more.

They have a fast metabolism and as such must eat 25% of their body weight each day.

Sea Otter

Range

Sea otters spend almost their entire life in the water. They can be found in the Pacific Ocean where they remain close to the coastline. Their range takes in the coastline of Canada, Japan, Mexico, Russia and the United States.

Habitat

These animals live in areas close to the shoreline. They are often associated with kelp forests which they will use at night when sleeping.

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Reproduction

Breeding may take place year round. Males mate with multiple partners throughout the year. Males will find a receptive partner and then remain with her during estrus. When they mate he holds her in his jaw and scars are often present on females due to this.

Only a single pup is born at a time. Pups are initially carried on the mothers chest. She must leave the pup at the surface when she dives and she may tie it in a kelp frond during this time.

Due to the presence of delayed implantation these mammals have a highly varied gestation of 4 to 12 months.

After two months they will start to move off and feed on their own. Independence is reached by six months old.

Females reach sexual maturity at 4 years old with males not maturing until 6 years old. Most females breed once every 2 years.

As few as 25% of sea otter pups survive to reach adulthood.

Behavior

Another adaptation which helps to survive in their cold environment, apart from the fur, is a layer of air which is trapped against the fur when they dive.

The dense fur of a sea otter requires regular maintenance to ensure it is clean and remains waterproof.

Their entire life is spent at sea apart from females who may occasionally come to shore to give birth or during periods of stormy weather. They are well adapted for swimming. Their lungs are 2 and a half times the size of a similarly sized land animal. This allows them to dive to 30m (98ft) below the surface and remain submerged for 4 minutes.

Sea otters are active during the day. By night they will wrap kelp around them which stops them floating away while they sleep.

These social animals are often seen in groups known as rafts. In some areas these groups grow to include hundreds of individuals.

Males are slightly territorial and may work to exclude other males from their territory. This may involve small fights or aggression by the intruder. They will allow females to move freely through the territory.

Males work hard to defend their territory against other males. Most fights never turn violent instead being settled by splashing and vocal contests.

They are equipped with a strong sense of smell and good eyesight both in and out of water which helps them to find food.

When swimming they travel at speeds of between 4.8 and 8km/h (3-5mph).

Sea Otter

Predators and Threats

Natural predators of the sea otter include killer whales, sharks, bald eagles, coyotes and brown bears.

As the availability of larger prey such as seals has declined predators such as killer whales have had to switch to the smaller sea otter.

In the 1700s it was estimated that there may be as many as 300,000 individual sea otters on Earth. By 1911 the animals had been hunted by near extinction but were afforded protection under the International Fur Seal Treaty. By this point as few as 2,000 sea otters were thought to remain.

A more recent estimate made from 2004 to 2012 placed the population at 89,000 in Alaska and 28,000 in Russia

In 1977 they were offered further protection under the Endangered Species Act.

Despite these larger numbers and the continued expansion of the population in areas where they have been reintroduced they are still considered to be decreasing.

Pollution in the water can prevent the air from trapping against their skin correctly. It can also be swallowed when they are grooming leading to health issues. This can cause them to die of hypothermia. Oil spills are now viewed as the largest threat to the species having overtaken hunting.

Fishing equipment presents a threat to this species as they can become trapped there.

The soft fur of the sea otter has long been sought by hunters and this saw them almost driven to extinction.

In parts of their range the sea otter is impacted by disease. Climate change is an emerging threat to this species.

Wear to the teeth is a major contributor to the death of adult animals.

Quick facts

Sea otters are the smallest species of marine mammal.

They have the densest fur of any mammal.

Sea Otter

Photo Credits

Top and Middle One

Public Domain

Middle Two and Bottom

mikebaird, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons

References

Burnie, D., 2019. Kingfisher Animal Encyclopedia. UK: Kingfisher Books Ltd.

Burnie, D., 2011. Animal. 3rd ed. London: DK

Jackson, T.,2011. The Illustrated Encyclopedia of Animals, Birds & Fish of North America. 1st ed. Leicestershire: Lorenz Books

Doroff, A. & Burdin, A. 2015. Enhydra lutris. The IUCN Red List of Threatened Species 2015: e.T7750A21939518. https://dx.doi.org/10.2305/IUCN.UK.2015-2.RLTS.T7750A21939518.en. Downloaded on 27 July 2021.

Oregon Zoo. 2021. Southern sea otter. [online] Available at: <https://www.oregonzoo.org/discover/animals/southern-sea-otter> [Accessed 27 July 2021].

Oceana. 2021. Sea Otter. [online] Available at: <https://oceana.org/marine-life/marine-mammals/sea-otter> [Accessed 27 July 2021].

Montereybayaquarium.org. 2021. [online] Available at: <https://www.montereybayaquarium.org/animals/animals-a-to-z/sea-otter> [Accessed 27 July 2021].

Allegra, J.; R. Rath and A. Gunderson 2012. "Enhydra lutris" (On-line), Animal Diversity Web. Accessed July 27, 2021 at https://animaldiversity.org/accounts/Enhydra_lutris/

Georgia Aquarium. 2021. Southern Sea Otter – Georgia Aquarium. [online] Available at: <https://www.georgiaaquarium.org/animal/southern-sea-otter/> [Accessed 27 July 2021].

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