NL·0548Herbarium of the Nature Library
- Name
- Enhydra lutris
- Family
- Mustelidae
- Native to
- Coastal North Pacific, from Hokkaido and the Kuril Islands through Alaska to California
- Habitat
- Kelp forest, Rocky coast, Estuaries
Sea otter
Enhydra lutris
Also calledKalan (Russian) · Rakko (Japanese) · Hǎitǎ 海獭 (Chinese) · Nutria marina (Spanish)
One of the smallest marine mammals, and unlike most it has no blubber, keeping warm instead with the densest fur of any animal. By eating sea urchins, sea otters protect kelp forests, a textbook case of a keystone species.
The sea otter is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Adult sea otters typically weigh between 14 and 45 kg (30–100 lb), making them the heaviest members of the weasel family, but among the smallest marine mammals. Unlike most marine mammals, the sea otter's primary form of insulation is an exceptionally thick coat of fur, the densest in the animal kingdom. Although it can walk on land, the sea otter is capable of living exclusively in the ocean. Wikipedia
What it can do
- iFloats on its back and cracks shellfish against a stone balanced on its chest
- iiKeeps a favourite stone in a loose pouch of skin under its forearm
- iiiHas fur of up to ~150,000 hairs per square centimetre, which traps an insulating layer of air
- ivControls urchin numbers, allowing kelp forests to grow and support many other species
In the field
Field marks
- aLarge otter floating on its back
- bDense brown fur, paler grizzled head
- cSmall ears, blunt face, flipper-like hind feet
- dUses rocks as tools on its chest
- Voice
- Squeals and whistles, especially from pups
- Not to be confused with
- Harbour seals lie belly-down and lack visible paws. River otters swim on their bellies with long, tapering tails.
- Where to see it
- Monterey Bay and Elkhorn Slough (California); Kenai Fjords and Prince William Sound (Alaska)
- When
- Resident
Listen
Looking for field recordings…
Life & habits
- Diet
- Carnivore: sea urchins, crabs, clams, mussels, snails; eats about a quarter of its body weight daily
- Habitat
- Shallow coastal waters, often within 1–2 km of shore
- Size
- 1–1.5 m; males 22–45 kg, females 14–33 kg
- Lifespan
- 10–20 years
Rafts of resting otters wrap themselves in kelp or hold paws so they don't drift apart. Mothers float their pups on their bellies.
Where it lives
Recorded sightings
—
geo-referenced records in GBIF, from museums, herbaria and field observers.
Native range
Coastal North Pacific, from Hokkaido and the Kuril Islands through Alaska to California
Drag the globe to turn it. Dots are where records exist, not a range map; darker means more records.
In the old herbals & bestiaries
No plate in the Source Library names this exact species, so these show its closest relatives as the old naturalists drew them: same genus, or the same kind of animal. Click a plate to read the page it came from, with translation.
The Hieroglyphics
Relative · Horapollo · 1551 · p.251
History of Animals, Book II: On Oviparous Quadrupeds
Relative · Conrad Gessner · 1586 · p.721
Theater of Earthly Creatures
Relative · Anonymous · 1672 · p.168
Florentine Codex, Vol. 3 (Books 10-12)
Relative · Bernardino de Sahagún · 1577 · p.456
Collected Illustrations of the Three Realms: Birds and Beasts
Relative · 王圻, 王思義 · 1609 · p.48
In the stacks
Searching the stacks…
Every page naming Enhydra lutris in the Biodiversity Heritage Library →
Marginalia
After Vitus Bering's 1741 expedition returned with pelts, Russian and later British and American traders sold sea otter fur to China, nearly wiping the species out. The 1911 Fur Seal Treaty ended the hunt when perhaps 1,000–2,000 remained.
Curiosity
Sea otters are among the few mammals other than primates known to use stone tools.
Kinship
Fact-checked: 1 correction made to this sheet. Photographs: iNaturalist contributors under the licences shown. Records: GBIF.org. Historical plates: Source Library (CC BY-SA 4.0; originals public domain). Summary text: Nature Library editors and Wikipedia (CC BY-SA). Medicinal and edibility notes are historical and educational, not advice. iNaturalist taxon 41860.