SEA OTTER: CHARACTERISTICS, HABITAT, REPRODUCTION, FEEDING - BIOLOGY - 2025

The sea ​​otter (Enhydra lutris) is a placental mammal that is part of the Mustelidae family. One of the fundamental characteristics is its coat. This is reddish brown and very dense, so much so that in a square centimeter of skin there are about 100,000 hairs.

In addition, this thickness is maintained throughout the year, since the molting process does not occur in this species. In this case, the shedding hair is gradually replaced by another.

Sea otter. Source: mikebaird

In relation to the extremities, the forelimbs are short and have retractable claws. The hindquarters are wide, webbed in shape. Also, the fifth finger is longer than the rest. These peculiarities make the sea otter an excellent swimmer, but on land it walks with clumsy steps.

This marine mammal lives on the eastern and northern coasts of the Pacific Ocean. As for its habitat, it prefers environments close to the coast, to dive and hunt its prey. Their diet is based on marine invertebrates and fish.

Subspecies:

Habitat and distribution

The sea otter is found in two coastal geographic areas of the Pacific. The first of these covers the Commander and Kuril Islands, off the coast of Russia, the Aleutian Islands, in the Bering Sea area, and from the coasts of the Alaska Peninsula to Vancouver Island in Canada.

As for the second region inhabited by this mammal, it spans the entire central coast of the state of California, in the United States. Thus, it is located from the island of New Year, to the north, to Point Sur.

The northern range is limited by sea ice, below 57 ° N, while the southern area, includes even the kelp forests, at 22 ° N.

There are three subspecies. One of these is Enhydra lutris lutris, which lives from the Kuril Islands to the Commander Islands, located in the western Pacific. The second is Enhydra lutris nereis, located on the coast of central California. The third, Enhydra lutris kenyoni, lives in southern Alaska and the Aleutian Islands.

In times past, sea otter populations have spread across the North Pacific, from the central Baja California peninsula in Mexico to northern Japan. The main cause of this reduction in geographic distribution was the fur trade.

- Distribution

At present, the species is in clear recovery, in some of the regions where it had been threatened. Thus, there are stable populations on the east coast of Russia, British Columbia, Japan, Alaska, Mexico, California and Washington.

Japan

Previously this species lived on the coasts of Hokkaido, however, today it is mainly found in captivity, in aquariums. One of these enclosures is the Suma Aqualife, in Kobe, which has a couple of these animals, with the intention that they can reproduce.

Russia

Within the entire range of Enhydra lutris, one of the most stable areas is Russia. Thus, it is found in Kuriles, Kamchatka and in the Commander Islands.

Alaska

In Alaska, the range of distribution is discontinuous. This species is mainly distributed in the Aleutian Islands and in Prince William Sound, located in the Gulf of Alaska, on the southwestern coast of that state.

Canada

Between 1969 and 1972, some sea otters were transported from Alaska to the west coast of Vancouver Island and British Columbia. The introduction was successful, giving rise to stable populations located from Cape Scott to the Broughton Archipelago, via Queen Charlotte. In the south, it extended to Tofino and Clayoquot Sound.

Washington

During 1960 and 1970, a group of sea otters were transferred from Amchitka Island, southwest Alaska, to Washington. Since 2017, its range has grown, spanning from Cape Flattery in the north to Point Grenville in the south. In relation to the east, it is located at Pillar Point, along the entire Strait of Juan de Fuca.

In this state, this species lives almost exclusively on the outer coasts, being able to swim at 1,830 meters along the coast.

California

Its range, although it has expanded gradually, has suffered great advances throughout history, but also great contractions. However, since 2010 the northern boundary has shifted from Tunitas Creek to an area 2 kilometers from Pigeon Point. In relation to the southern boundary, it moved from Coal Oil Point to Gaviota State Park.

Mexico

In this country, the Enhydra lutris was considered extinct, however, today there are some small populations on the coasts of the Baja California peninsula.

- Habitat

Throughout the area where they are distributed, sea otters inhabit a wide variety of marine ecosystems near the coast. Generally, foraging occurs within a range of one kilometer from the coastal zone.

Regarding the depth of immersion, the maximum recorded was 97 meters. However, recent studies indicate that the average foraging of females was 54 meters, while males do it at 82 meters.

This species is frequently associated with rocky substrates, where beds of marine algae, such as Macrocystis pyrifera, abound. However, it could be located in areas of soft sediments, where algae are not very frequent.

The areas where you live are protected from strong ocean winds, such as on rocky shores, barrier reefs, and kelp forests. In relation to the range of home, it usually covers a few kilometers long and they tend to stay in it throughout the year.

State of conservation

In times past, Enhydra lutris populations were hunted to near extinction in their natural habitat. However, at the beginning of the 20th century, Russia, the United States, Great Britain and Japan signed an agreement prohibiting the hunting of marine mammals.

Although this and other actions have led to a decrease in their capture, to commercialize their skin, this species continues to be threatened. This is why the IUCN categorizes the sea otter as an endangered species.

- Threats

Oil spills

The main anthropogenic threat to the sea otter is the oil spill in the waters where it lives. This affects otters, because their skin remains oily, thus losing its insulating property from the cold. In this sense, because these animals lack a protective fat layer, they die of hypothermia.

Also, the oil could be ingested while cleaning, causing serious gastrointestinal upset, which could lead to death. Likewise, the volatile components of the oil are inhaled, causing lung damage.

Incidental fishing

Sea otter death statistics in California indicate that a large number of cases are due to accidental drowning in gillnets. This situation is aggravated during the summer months, when commercial fish landings increase in coastal regions.

Climate change

Climate change causes severe alterations to the climate, the acidification of the waters and the frequency in the occurrence of atmospheric events, such as El Niño.

All these ecological alterations can vary the availability of food, thus modifying the feeding behavior of this animal. In addition, they can affect reproduction, causing the loss of young.

Infectious diseases

Experts determine that infectious diseases, such as endocarditis, distemper, and encephalitis, are a major factor in mortality in some of the sea otter populations. In addition to this, the species is affected by parasites such as Toxoplasma gondii and Sarcocystis neurona.

Predators

Predation by the killer whale (Orcinus orca) caused the population decline of sea otters that inhabited the western Gulf of Alaska and the Aleutian Islands.

Also, this marine mammal is threatened by great white sharks (Carcharodon carcharias), coyotes (Canis latrans), brown bears (Ursus arctos) and bald eagles (Haliaeetus leucocephalus).

- Conservation actions

The subspecies Enhydra lutris nereis is on Appendix I of CITES, while the rest of the subpopulations are included on Appendix II.

In Canada, sea otters are under the Endangered Species Act. In relation to the United States, they are protected by the Marine Mammal Protection Act of 1972 and, particularly in California and Alaska, they are protected by the Endangered Species Act of 1973.

Since 1972, Enhydra lutris has been protected by the US Marine Mammal Protection Act, which prohibits the harassment and capture of marine mammals.

Reproduction

In this species, the female becomes sexually mature between four or five years. However, some may mate at 3 years. As for the male, at five years old he is able to reproduce, although in most cases they do not do so until two or three years later.

The sea otter can breed throughout the year. However, there are variations associated with geography. Thus, those that live in the Aleutian Islands have birth peaks from May to June, while in California, the offspring are usually born from January to March.

Enhydra lutris is polygamous, so the male has several partners during the reproductive stage. When the male establishes a territory, he generally defends it with vocalizations, thus avoiding fights.

Mating

When the male gets a receptive female, which may or may not be in his territory, they both engage in behaviors that could become aggressive. During copulation, which occurs in water, the male supports the female's nose or head with her teeth. This leaves visible marks on your partner's body.

The ovum, once fertilized, does not attach itself to the uterus, but is subjected to late implantation. In this way, the embryo develops later, in the best conditions for the birth of the young.

As for the gestation, it can vary between four and twelve months. The delivery is in the water and generally the litter is of a single calf.

Breeding

The calf weighs between 1.4 and 2.3 kilograms. At birth, their eyes are open and 10 teeth can be seen on their jaw. It has a thick coat of hair, which the mother licks for hours. After that time, the newborn's fur is fluffy and has so much air trapped that it keeps floating in the water, without being able to dive.

Breast milk is rich in fat and is offered to the young for a period of six to eight months in California populations and four to twelve months in Alaska. After that time, the mother begins to offer him small prey.

The female is the one who performs the rearing and feeding tasks of the young, including those that have been orphaned. When you go out in search of food, you can leave the youngster floating in the water, wrapped in algae to prevent it from wandering away.

In the presence of a predator, the mother holds the cub by the neck with her mouth and dives into the water. The young person is usually independent when he is between six and eight months old.

Feeding

Enhydra lutris is carnivorous, consuming between 20 and 25% of its body weight daily. This is because, due to its high metabolic rate, it requires burning the necessary calories that allow it to counteract the loss of heat it suffers, due to the coldness of the water where it lives.

This species will devour almost any variety of marine invertebrates or fish that it can find in its foraging area.

Among the benthic invertebrates are sea urchins (Strongylocentrotus purpuratus and Strongylocentrotus franciscanus), coastal mussels (Mytilus edulis), starfish (Pisaster ochraceus), rock scallops (Crassadoma gigantea) and chitons (Katharina tunicata). They also eat crabs, squid, and octopus.

Hunting methods

The sea otter hunts by making short dives, which do not last more than four minutes. When submerged, it can use its front legs to lift and dump rocks in search of prey. In addition, it plucks snails from the algae and burrows into the seabed.

Likewise, it is the only marine mammal that catches fish with its forelimbs, instead of with its teeth. He also uses the rocks to hunt. Either to hit the prey against them, or to use it as a hammer and thus take off a mollusk, such as abalone, that is attached to a surface.

This species eats while floating in the water on its back. Along with this, it uses its front legs to separate the food and bring it to its mouth.

Behavior

The sea otter is a not very territorial animal. Only in adulthood does it usually establish and defend its territory. In these areas, the male watches the boundaries, attempting to remove other adult males from the area. However, the female can move freely through this area, resting in a space that is separate from that occupied by the male.

Although your habits are generally daytime, you can be active at night. The feeding period begins in the morning, before sunrise. Then rest until noon.

During the afternoon, the search for food resumes, ending at dusk. In some cases, a third feeding stage usually occurs, around midnight.

To sleep or rest, the Enhydra lutris floats on its back and wraps its body in seaweed to avoid drifting. In this position, the back legs stick out of the water and the front legs are bent over the chest or covering the eyes.

This species has a very marked grooming habit. They carefully clean and groom their fur, in order to maintain its thermal insulating capacity to the maximum.

Communication

To communicate, use body contact and calls. Although it is a low vocal mammal, researchers have distinguished nine different vocalizations. For example, hatchlings use squeaks to communicate with their mother. Other sounds include moans, cooing, grunting, hissing, and screaming.

References

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