Mammals · Mustelids

Sea Otter

Enhydra lutris

Endangered

The sea otter is the heaviest member of the weasel family and among the very few marine mammals that use tools. Found along the North Pacific coast, it relies on the densest fur of any animal on Earth — rather than blubber — for warmth, and plays an outsized role in keeping kelp forest ecosystems healthy.

Classification

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Carnivora

Family: Mustelidae

Genus: Enhydra

Species: lutris

Related species: River otter, giant otter, weasels, badgers — all family Mustelidae

Size

4–5 ft long including tail; the largest member of the weasel family by weight.

Weight

45–90 lbs, with males considerably larger than females.

Habitat

Nearshore kelp forests and rocky coastlines of the North Pacific, from California to Alaska and across to Russia and Japan.

Description

Dense, dark brown fur (paler on the head in older individuals), a blunt face with prominent whiskers, and webbed hind feet used for propulsion.

Fur density

Up to 1 million hairs per square inch — the densest fur of any animal — trapping an insulating layer of air rather than relying on blubber for warmth.

Diet

Carnivore — sea urchins, clams, crabs, mussels and other invertebrates, eating up to 25% of its body weight daily to fuel its fast metabolism.

Tool use

One of the few marine mammals known to use tools, cracking open shellfish with a rock balanced on its chest while floating.

Communication

Squeals, whistles and grunts; mothers and pups also recognize each other’s individual calls at a distance.

Gestation

About 4–12 months, varying due to delayed implantation.

Birth & Litter Size

Usually a single pup, born with a coat so buoyant it cannot yet dive, kept afloat on the mother’s chest for weeks.

Sexually Mature

3–5 years for females, 5–6 years for males.

Life Span

10–20 years in the wild.

Did You Know?

A sea otter has up to a million hairs per square inch of skin — more hair on a single square inch than a human has on their entire head.

Did You Know?

Sea otters often hold hands, forming a "raft," while sleeping to keep from drifting apart on the current — mothers will also wrap their pups in kelp to anchor them in place.

Did You Know?

A sea otter has a favorite rock, kept tucked in a loose pouch of skin under its forelimb, which it uses over and over as a tool to crack open shellfish.