Sea Otters: Characteristics, types, habitas and more

It is time to learn all what you ever wanted about these beautiful and lovely creatures called sea otters

Sea otters are semi-aquatic mammals belonging to the subfamily Lutrinae, and the Mustelidae family (the same of the weasels) and stand out for their playful behavior. It is important to note that this species is not the same as the marine otters (Eurasian otters) which are sometimes also called sea otters.

The sea otters were scientifically described for the first time by the German zoologist Georg Steller (March 10, 1709-Tiumén, November 14, 1746)) in field notes in the year 1751.  A few years later, the Swedish botanist Carlos Linnaeus (May 23, 1707-January 10, 1778) also described them in his work Systema Naturae which was written in 1758. Their current scientific name Emhydra Lutris was given in 1922, and means otter in the water.

sea otters : basic information

Main Characteristics Of  The Sea Otters


Their measurements vary depending on the sex. Adult males weight between 22 and 45 kilograms and measure from 1.2 to 1.5 meters. On the other hand the adult females usually weigh between 14 and 33 kilograms, and their length varies from 1 to 1.4 meters.

The sea otters have a flexible skeleton and their face is small and round. Their legs are flat, long and wide, and have retracted claws similar to that of a cat, which allows them to take their prey firmly.

The females have two breasts in the abdomen and their tails are very short slightly flattened and muscular. Adult sea otters have 32 teeth. The molars are flattened and rounded and are used to crush and not to cut. They have two inferior incisors, which is a curious trait because they are the only carnivores that do not have three.



The Marine otter lack of a thick skin of fat, unlike other marine mammals. They depend exclusively on their dense fur to protect themselves from the cold. These beautiful species have 150,000 hairy filaments per square centimeter in their skin, which is the highest concentration in any mammal species. Their coat is made up of several layers.  The outer one is hair, and is long and waterproof, so it helps the bottom layer to stay dry, as well as insulates the cold water completely and limits heat loss.

Their inner cover is shorter, and has the property of trapping air to form an insulating layer against cold water since they don´t  have insulating fat. The sea otters molt their fur constantly (do not perform seasonal molting), which allows them to have a thick coat all year round.

To keep the heat of their bodies, these creatures tend to groom themselves in order to keep their cover in good condition. Their fur´s coloration is usually dark brown with silvery grey spots, although some specimens may have a yellowish, greyish brown or almost black color.

Adult specimens present in their head, neck and chest, a lighter tonality than in the rest of their body. As in the case of many species of seals  the sea otters were hunted by their fur to the point of almost extinction. At the beginning of the twentieth century, only 2,000 animals remained. Today, sea  otters are protected by several laws.

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Other Characteristics of the Sea  Otters

  • The sea otters can close their  nostrils and their auditory passages in the water.
  • The fifth toe of each leg is longer, which allows them to swim more easily, but hinders their movement on land.
  • Their body has great agility to float, due to the excellent lung capacity of these otters, and the air that can trap their internal coat.
  • They can walk but in a somewhat clumsy way, usually moving with small jumps.
  • Sea otters have very sensitive whiskers and plantar pads, which help them find their prey in turbid waters.
  • Some scientists suggest that their smelling sense is more important for them than their sense of vision, especially when they are under surveillance.
  • Other studies say that their vision of sight is useful in both water and land, but is not as developed as that of seals.

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Types of Sea Otters

There are three known subspecies of sea otters, which differ only by their body´s size and some other individual characteristics of  their teeth  and skulls.

Common Sea Otter.

Its scientific name is Emhydra Lutris Lutris Linneo, and it is also called Asian sea otter. It is distributed from the Kuril Islands located in Japan, to the Commander islands of the in the Western Pacific. These creatures are large and have a wide skull with short nasal bones.


Southern Sea Otters

Their scientific name is Emhydra Lutris Nereis Merriam and they are located on the coasts of Central California. They are also called California Sea Otters. They have a smaller skull with a long face and small teeth. This species is considered to be at risk of extinction, which is why it is listed in the Federal Species Act (ESA) since 1977. It is also protected under California state law.

The northern Sea Otters.

Their scientific name is, Emhydra Lutris kenyoni. These otters inhabit Alaska and the western Pacific coast, from the Aleutian Islands to British Columbia, northern Oregon and Washington. After being exterminated in southern British Columbia due to overhunting, they have been reintroduced to the outskirts of Vancouver Island and the Olympic Peninsula.

In this sense, the efforts to introduce them again in the coasts of Oregon have not been successful. But there was a positive result in Washington between 1969 and 1970, with the constant increase of their range of distribution and population.

How Much Do Sea Otters Live?

When they are in their natural habitats, otters live for a maximum of twenty years, with a life expectancy of ten to fifteen years in the case of males, and from 15 to 20 years in females. When these creatures are in captivity, they have a slightly larger longevity, surpassing even the 20 years.  The longest-lived specimen, of which there are records, was a female in the Seattle Aquarium, which died having 28 years of life. It is common for them to suffer deterioration in their teeth when they are in their habitats, which is thought to shorten their lives.

Where Do  Sea Otters Live?

The sea otters inhabit the North Pacific from northern Japan to Baja California in Mexico. They live mainly in coastal waters that have a depth of fifteen to twenty meters. The sea otters remain near the coast less than a kilometer away from it, and are commonly observed in protected areas of strong oceanic winds, such as rocky shores, dense forests of seaweed and reef barriers.

However they also occupy to a lesser extent oceanic areas with sand, mud or muddy floors. In the North, their distribution is limited by Arctic ice edges, and may also be in areas with drifting ice, but it quite hard for them to survive on fixed ice.

They usually occupy an area of one kilometer-long territory and remain in it for a whole year. It is believed that there are around 150,000 and 300,000 specimens along the North Pacific from northern Japan to Baja California in Mexico. Currently there are areas where their population is stable in countries such as Russia, Alaska, British Columbia, Washington and California.


It is the safest and also stable territory where the marine otters inhabit. They are mostly found in Kamchatka and the major islands; however the growth of their population has recently slowed down, because it has reached the country´s capacity to sustain this species.

British Columbia

In 1969 they moved from Alaska, eighty-nine Otters to the Vancouver islands in British Columbia, which began a healthy population. According to several statistics in 2004 there were about 3,000 animals in this area. In 1989 an independent colony was discovered on the coast of British Columbia, which had about 300 individuals who according to some investigators could be transported otters who survived the fur trade. In 1980 the FWS relocated 140 California sea otters on San Nicola Island to save them from an oil spill, however the population was quickly reduced surprising the scientists.  Apparently the otters returned to their former habitat. In the years 2004 and 2007 were conducted population studies, according to which there are around the world an approximately 107,000 specimens.

What Do Sea Otters Eat?

Sea otters eat sea urchins, abalone, mussels, clams, crabs, snails and other 40 marine species. They eat about 25% of their weight in food each day due to their accelerated metabolism. They open the shells of some of their prey, with stones and a piece of wood.  They have a kind of pocket that forms with loose skin extended through their thorax, in which they keep their food while they are submerged and then come out to the surface and feed as they float on their backs.

How do the Sea Otters Hunt Their Prey?

To capture their prey, they carry out short dives to the bottom of the sea for up to five minutes. They are the only mammals that can lift and turn rocks at the bottom of the sea, action that  they carry out continuously to look for prey. They regularly shed snails attached to the algae and can dig in mud for clams. The sea otters don´t catch the fish with their mouth, but with their front limbs.

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Sea Otters’ Behavior

They remain in the water most of their time, and they can dive 100 meters away to look for food. They can also move across the surface, but very clumsily. They move with small jumps, and spend a long period of time grooming (up to 10% of their time,), cleaning their coats with their paws and have good reasons to do this: it helps them to remain waterproof and isolated against the cold.

Social Structure

Although they usually hunt individually, it is not weird to see them resting together in groups of the same sex called Rafts. These groups are made up of ten to one hundred individuals. Groups of males are more numerous than those composed of females. Even groups of more than two thousand individuals have been seen resting at the same time, and it is believed that this practice is carried out to avoid being dragged by the sea and get lost adrift.

The struggles between sea otters are not frequent and they have a varied vocal behavior. The females commonly whisper when they are happy, while the males groan when they are exalted. When they are scared or sad they can whistle, hiss or in extreme situations scream. It is said that the sea otter is sociable and playful although they spend most of their time alone.

How Do Sea Otters Reproduce?

These creatures have a very peculiar reproduction cycle. Their mating system is polygamous and they show a highly significant sexual dimorphism. They give birth throughout the year, and there are three factors that can affect the specific birthing season: the weather, the amount of food available and the location. The females are not sexually mature until they are three years old. As for males, they reach sexual maturity when they are between 5-7 years of age. The reproduction process begins with the males wooing the females. When courting, males tend to swim upside down, moving faster than normal. When found near a female, the male tries to hug her or sniff her body. If the female is interested, she starts spinning on the ground and fiddles for a while. If not, she pushes him, as a rejecting signal. The two will usually separate from the group for a few days and this is when mating begins.

During mating, the male tightens his teeth against the female’s nose and also wraps her chest with his forepaws to cling to her. During the reproduction cycle, the females are nicknamed Rudolph because after mating the female’s nose is a bloody red. The mating only lasts between 15 and 30 minutes, which tend to be very vigorous and intense for both women and men. The sea otters’ gestation period is much longer than that of other otters. It lasts between 4 and 12 months. After the fertilization takes place, the egg undergoes a series of changes. As it travels through the fallopian tubes from the ovary to the uterus, it divides several times and then reaches a stage called a blastocyst. Next, sea otters go through a phase called delay in implantation and development is suspended for several months or days. This phase usually lasts between two and three months.

Sea otters give birth to their young in the water and very rarely give birth on earth. After childbirth, the female observes her puppy and prepares his fur on her chest during the first hours. Newborn otters are extremely defenseless because they are blind and not very mobile.

The otters’ rate of growth is very slow. The first attempts to swim take place at approximately three months, but diving takes more time. After four months, they follow the female on night trips for food. Approximately 8 months after birth, the puppy begins to go out alone and begins to take care of himself. Female sea otters have an average litter size of 1 puppy. Occasionally, the female can give birth to twins, but the female only cares for one of the puppies and the other usually dies.

Sea Otters’ Main Threats

It is estimated that the world sea otters’ population once numbered between several hundred thousand and more than one million before being almost exterminated by fur traders in the 18th and 19th centuries. Sea otters finally obtained protections with the signing of the International Sea Lion Treaty in 1911, and were included in the List of Protection against Marine Mammals and Endangered Species Laws in the 1970s. Worldwide, numbers have recovered slowly but are still far below the original population numbers. While sea otters are vulnerable to natural predators, their populations are also significantly affected by several human factors, Such as those mentioned below.

Oil Spills

Oil spills from offshore drilling or shipping are a huge threat to sea otter populations

Sharks attacks

The range of marine otters’ habitat is expanding due to the lack of food in its current range. Unfortunately, at the limit of their range, sea otters bitten by sharks now account for more than half of the dead animals found.

Conflict with humans

Direct conflict with humans, such as shooting and entanglement in traps and fishing nets, pose a great threat to sea otters’ populations.

 Habitat  Degradation

The oceans’ pollution, affects deeply the sea otters’, since endangers their food sources, and directly harms them. Sea otters are often contaminated with toxic pollutants and disease-causing parasites as a result of runoff in coastal waters.

Preserving the Sea Otters

Their environment has been protected by means of some protected areas in the USA, Russia and Canada. In these areas polluting actions such as the dumping of oil residues are prohibited. There are approximately 1,200 individuals in the Marine National Sanctuary of Bahia de Monterrey and more than 500 in the National Marine Sanctuary of the Olympic Coast. The ESA developed a law  in 1973 to protect endangered and threatened American species, which requires recording the species in danger of extinction as well as making plans for their recovery.

The ESA creates rules on how to treat existing populations of endangered and threatened animals, and prohibits buying, selling or possessing any part of species or object made of them.  In addition, agrees to make efforts to recover the species, which means to create and develop a plan to recover them at healthy population levels. Thanks to these conservation organizations it was possible to achieve the recovery of the species, and the current goal is to reach the proper amount of individuals.

Sea Otters Could Save Our World

Sea otters also have a very important role for our planet. In the habitats from which they have disappeared for any reason, the sea urchins, (their main prey) obviously increase in size and number with devastating consequences. The algae forests of such habitats tend to disappear instantaneously as they are devoured by sea urchins. In fact, it is now recognized that sea otters are a key species, whose position in the food chains is crucial to maintain the ecological health of an area. Not only do they ensure the health of algae forests but they also affect many other local species that grow in seaweed forests, such as mussel beds, for example.  But above all, those rich forests of marine algae, enriched by the activity of the sea otters, play a key role in the maintenance of global environmental health. The levels of carbon dioxide in the atmosphere are increasing both in the sea and in the atmosphere, and the sea is absorbing them more and more, which makes it more acidic and harmful for many species. The healthy forests of algae absorb around 43 billion kg of carbon dioxide to carry out their process of photosynthesis, which is a factor that has become essential to ensure the existence of the planet earth. A sign that biodiversity is essential. This information was provided by James Estes, an American marine biologist who has studied wildlife in the North Pacific Ocean for the past 45 years.

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