Sea otter

They can sleep in the sea by lying on their backs and floating on the surface of the water

Mike Michael L. Baird

Sea otter


They can sleep in the sea by lying on their backs and floating on the surface of the water

Population 3,000
>90% decline from 1990 – 2015

As the heaviest member of the weasel family yet the smallest marine mammal, the sea otter presents a study in contrasts and an example of nature’s adaptability. Native to the northern and eastern coasts of the Pacific Ocean, these marine mammals have developed remarkable biological and behavioral adaptations to thrive in their aquatic environment.

One of the most notable features of the sea otter is its dense fur, the thickest in the animal kingdom. This luxurious coat comprises a dual-layer system: a short undercoat that traps air and a layer of longer guard hairs that protect the undercoat. This fur ensemble serves a critical function, providing insulation against the cold waters of the Pacific Ocean. Sea otters lack the blubber that other marine mammals rely on for warmth, making their fur essential for their survival.

To maintain the insulating properties of their fur, sea otters engage in meticulous grooming behaviors. After feeding, they use their teeth and paws to clean their coat, ensuring that they remain waterproof and able to trap air effectively. This behavior underscores the importance of their fur for thermoregulation and buoyancy.

Sea otters play a pivotal role in their ecosystem, particularly in maintaining the health of kelp forests and coastal marine habitats. They are keystone species, meaning their presence has a disproportionately large impact on their environment. By preying on herbivores such as sea urchins, which can overgraze kelp if left unchecked, sea otters help preserve kelp forest ecosystems that provide habitat for many marine species.

The tragic history of sea otter exploitation for their fur led to a drastic decline in their population, pushing them to the brink of extinction. From an estimated 300,000 individuals in the 18th century, relentless hunting reduced their numbers to a mere 2,000 by the early 20th century. Thanks to international protection and conservation efforts, their numbers have gradually increased, but they remain listed as Endangered by the IUCN.


Population est.
Seasonality Uncertain
Seasonality Uncertain
United States

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Terrestrial / Aquatic

Altricial / Precocial

Polygamous / Monogamous

Dimorphic (size) / Monomorphic

Active: Diurnal / Nocturnal

Social behavior: Solitary / Pack / Herd

Diet: Carnivore / Herbivore / Omnivore / Piscivorous / Insectivore

Migratory: Yes / No

Domesticated: Yes / No

Dangerous: Yes / No