- Also called:
- great sea otter
sea otter
-
What is a sea otter?
The sea otter (Enhydra lutris) is a marine mammal of the northern Pacific, often found in kelp forests. They can grow to be between 100 and 160 cm long and weigh between 16 and 40 kg.
Sea otters eat while floating on their backs, and they are known to use rocks as tools to crack open the hard shells of prey such as crabs and shellfish. They mainly feed on sea urchins, crabs, and shellfish. To avoid drifting away while sleeping, they float on their backs, sometimes holding each other's forefeet to create large rafts.
The sea otter was once hunted to near extinction for its fur. Though protected by the North Pacific Sealing Convention of 1911 and other conservation measures, pollution, conflicts with fisheries and predation continue to threaten the species.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Where do sea otters live?
The sea otter (Enhydra lutris) is a marine mammal of the northern Pacific, often found in kelp forests from the Kuril Islands to the Aleutian Islands and south to the coast of California. They spend most of their time in the ocean but occasionally come to shore to rest or escape predators. Sea otters can gather in groups of up to 1,000, grasping each other's forefeet to create large rafts or pods. Sea otters are well adapted for marine life, possessing fully webbed front and back feet, large lungs, thick fur for insulation, and the ability to drink salt water, allowing them to stay at sea for days.
4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What do sea otters eat?
Sea otters are marine mammals that eat food found in their aquatic habitats such as sea urchins, crabs, and other shellfish. They will also eat fish.
While floating on their backs, they will use rocks as tools to crack open their hard-shelled prey. Sea otter predation on sea urchins allows kelp forests and fish to flourish.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How do sea otters keep warm in cold water?
Sea otters, the smallest marine mammals, possess unique adaptations to stay warm in chilly waters. Unlike other marine mammals, they lack a blubber layer. Instead, they rely on their exceptionally dense fur, the densest of any mammal, with up to a million hairs per square inch, to insulate themselves. This thick pelt traps air, creating a barrier against the cold. Additionally, sea otters have a high metabolism that generates body heat, and they sometimes come to shore to warm up.
4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How do sea otters use tools to get their food?
Sea otters are marine mammals that use tools to access food in their aquatic habitats. They have a unique feeding strategy where they float on their backs and use rocks as tools to crack open the hard shells of prey like crabs and shellfish. While floating, they will smash mollusks against a stone balanced on their chest. They also crush sea urchins with their forefeet and teeth. Sea otters' diet of sea urchins helps kelp forests to flourish.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Why are sea otters important for their ocean habitats?
Sea otters play a crucial role in maintaining the health and balance of their ocean habitats. As a keystone species, their presence has a significant impact on the structure and function of the ecosystem.
Sea otters are voracious predators of sea urchins. By feeding on these herbivorous urchins, sea otters prevent them from overgrazing kelp forests. Kelp forests provide habitat and food for numerous other marine species, including fish. Without sea otters, sea urchin populations can explode, leading to the destruction of kelp forests and the loss of biodiversity.
The decline of sea otter populations can trigger trophic cascades, where the removal of a top predator has cascading effects throughout the food web. The conservation of sea otters is, therefore, essential for maintaining healthy and resilient coastal ecosystems.
4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
sea otter, (Enhydra lutris), completely marine otter species of the northern Pacific, usually found in kelp beds. Floating on its back, it opens mollusks by smashing them on a stone balanced on its chest. The large hind feet are broad and flipperlike. The thick lustrous coat is reddish to dark brown. The sea otter is the largest otter, reaching 100–160 cm (40–65 inches) long and weighing 16–40 kg (35–90 pounds) when fully grown. It inhabits coastal waters from the Kuril Islands to the Aleutian Islands southward to the coast of California.
Diet and natural history
Sea otters feed mainly on sea urchins and on crabs and other shellfish. The captured prey is eaten at sea while the otter swims on its back. Rocks are typically used to break open crabs and other shellfish, whereas sea urchins are crushed with the forefeet and teeth. Consuming herbivorous urchins (genus Strongylocentrotus) enables kelp forests and the fish associated with them to flourish. However, large numbers of sea otters can deplete shellfish populations, competing with fisheries for crabs, clams, and abalones. Female sea otters give birth in water to only one young at a time, and the young remains dependent on the mother until six to eight months of age.
(Read Britannica’s essay “How Do Sea Otters Stay Warm?”)
" height="20" alt="HEW Logo">
Although sea otters spend most of their time in the ocean, they come to the shore on occasion to escape predators in the water, rest, or warm up. Often resting near beds of kelp, where they rely on their buoyant bodies to float on their backs, sea otters can gather in groups of up to 1,000 individuals, grasping one another’s forefeet to create large rafts or pods.
Conservation status
The sea otter had been hunted almost to extinction for its fur by 1910. After becoming aware of this diminishing resource, the United States, Great Britain (for Canada), Japan, and Russia signed the North Pacific Sealing Convention in 1911 to protect sea otters and northern fur seals (Callorhinus ursinus). Sea otters recovered modestly during the 20th century; however, their populations remain widely separated. Although the International Union for Conservation of Nature and Natural Resources listed the sea otter as a species of least concern in 1996, population declines since the 1980s due to the effects of pollution from oil spills, conflicts with fisheries, predation by sharks and killer whales, and disease prompted the organization to reclassify the sea otter as an endangered species in 2000.
Marine otter
Some authorities also consider the marine otter (Lontra felina), a species that lives along the rocky Pacific coast of South America, to be a type of sea otter, because it hunts in shoreline and nearshore ocean areas, preying on crabs and other marine invertebrates. Unlike its northern cousin, however, the marine otter spends much more time on land, where it makes its dens in sea caves, along windswept beaches, or in gaps within rock outcrops.