Sea Otter (Enhydra lutris)

Marine MammalMustelidKelp Forest

Overview

The sea otter (Enhydra lutris) is the smallest marine mammal and the most fully aquatic member of the weasel family. It lives along the northern Pacific rim, spending almost its entire life at sea — feeding, resting, grooming and even giving birth in the water.

Sea otters have no blubber. Instead they rely on the densest fur of any animal, which traps a layer of air against the skin. That fur only works if it is meticulously maintained, so grooming occupies a large part of every day, and oil contamination is catastrophic for them.

To fuel a high metabolism in cold water, a sea otter must eat a very large share of its body weight daily — which is what makes it such a powerful force in the ecosystems it inhabits.

Habitat & Range

Sea otters live in shallow coastal waters along the North Pacific — from northern Japan and the Russian Far East through the Aleutians and Alaska to British Columbia and California. They favour rocky nearshore habitat with kelp forests, where they can forage on the seabed and anchor themselves in kelp fronds while resting.

Diet

Sea otters eat marine invertebrates: sea urchins, crabs, clams, mussels, abalone, snails, and some fish and octopus depending on region. Individual otters often specialise on particular prey and techniques. Because they burn energy fast in cold water, they consume a very large proportion of their body weight each day.

Behavior

Sea otters are among the best-known tool users outside primates and birds: an otter will carry a suitable stone and use it to crack hard-shelled prey against its chest while floating on its back, sometimes storing the stone in a loose skin pouch under the foreleg. They rest at the surface in single-sex groups called rafts and wrap themselves in kelp to avoid drifting. Grooming is constant, and pups are cared for intensively by the mother.

Human Interaction & Conservation

Sea otters were hunted almost to extinction in the maritime fur trade for their exceptional pelts, and surviving remnant populations have since expanded under protection. They are widely cited as a keystone species: by eating sea urchins they limit urchin grazing on kelp, helping kelp forests persist — an effect with consequences for many other species. Modern threats include oil spills, entanglement, disease, predation and conflict with shellfish fisheries. Verify current status at the IUCN Red List.