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27 / Recently extinct
Steller’s Sea Cow
Hydrodamalis gigas
This enormous, slow sirenian grazed kelp in cold shallow water.
- Time range
- About 8 million years ago–1768
- Final stage
- 18th century
- Geographic range
- Commander Islands, Bering Sea
01 / ANSWER FIRST
What was Steller's Sea Cow?
Steller's Sea Cow was an enormous cold-water sirenian, up to about eight metres long, that grazed kelp in shallow seas around the Commander Islands.
Georg Wilhelm Steller described it alive in 1741 after the surviving population had become restricted to a tiny refuge. Fur-hunting crews then killed it for meat and fat, and it was gone by 1768.
02 / QUICK FACTS
Steller's Sea Cow at a glance
- Scientific name
- Hydrodamalis gigas
- Extinction
- 1768
- Length
- Up to about 8 m
- Mass
- Several tonnes
- Diet
- Kelp and other seaweeds
- Teeth
- None; keratinous chewing pads
- Range at discovery
- Commander Islands
- Closest living relatives
- Dugongs and manatees
03 / CORE QUESTION
Why did Steller's Sea Cow go extinct?
Its final population lived in shallow, predictable kelp beds and moved slowly near the surface. Hunting crews killed animals for large quantities of meat and oil, removing adults from an already restricted and probably small population.
Hunting is the direct historical cause. Earlier range contraction may reflect post-Ice-Age habitat change, and sea-otter depletion may have altered kelp forests indirectly, but those mechanisms do not replace the documented slaughter.
Read the complete extinction-evidence guideHow to read the numbers
This page separates direct evidence, comparative inference and unresolved debate.
04 / LIFE & DISCOVERY TIMELINE
Twenty-seven years from scientific discovery to extinction
North Pacific range
Fossils extend from Japan to North America.
Steller observes survivors
A shipwrecked expedition documents the species.
Intense hunting
Fur-trade crews provision ships with sea-cow meat.
Last accepted killing
The species disappears from the Commander Islands.
05 / ANATOMY
A giant sirenian adapted to cold kelp forests
Thick hide
Dark, cracked skin and blubber insulated the body.
Small flippers
Forelimbs steered and braced against rocks while feeding.
Forked tail
A broad horizontal fluke supplied propulsion.
Chewing plates
Keratinous pads crushed tough seaweed without teeth.
06 / DIET & BEHAVIOUR
What did it eat?
Steller watched animals crop kelp and other macroalgae in shallow water, often exposing part of the back while feeding.
Read the complete guide07 / DIET & BEHAVIOUR
How did it live socially?
Historical accounts describe pairs, calves and groups assisting wounded animals, but sample size and observer interpretation limit detailed social claims.
08 / RANGE & HABITAT
Where did Steller's Sea Cow live?
At European discovery it survived only around Bering and Medny islands, but fossils show a formerly broad North Pacific coastal range.
Bering Island
The 1741 expedition made its first detailed observations.
Medny Island
Kelp beds supported the last population.
North Pacific fossils
Older bones occur from Japan to California.
Shallow rocky coasts
Cold productive kelp habitat supplied food.
09 / FOSSIL EVIDENCE
How do scientists know about Steller's Sea Cow?
Steller's account
A trained naturalist described living anatomy and behaviour.
Skeletons
Museum bones constrain size and sirenian identity.
Fossil range
Older remains document contraction before 1741.
Ancient genome
DNA tests population history and skin adaptations.
10 / DISAPPEARANCE & DEBATE
Was extinction inevitable before Europeans arrived?
No. The population was restricted and vulnerable, but it persisted until sustained hunting removed breeding adults over only a few decades.
Genomic vulnerability and habitat history explain risk; the historical record identifies the terminal pressure.
12 / FREQUENTLY ASKED QUESTIONS
Steller's Sea Cow FAQ
When did Steller's Sea Cow go extinct?
The last accepted record is 1768.
How big was it?
Up to about eight metres and several tonnes.
What did it eat?
Kelp and other large seaweeds.
Why did it go extinct?
Intensive hunting eliminated its final small population.
Did it have teeth?
No, adults used keratinous chewing pads.
Where did it live?
At discovery, only around the Commander Islands.
04 / SOURCES & FURTHER READING
Check the source record
Use the scientific name to compare taxonomy, occurrence records and the fossil record. Database coverage and classifications may differ.
05 / REVISION HISTORY
How has this record changed?
- Expanded into a bilingual S-tier hub with two evidence-led guides.
- Verified authoritative entity sources and added three responsive reconstruction sizes.
- Initial bilingual species record published.
06 / CORRECTIONS & ADDITIONS