Steller's sea cow
Hydrodamalis gigas (Zimmermann, 1780)
Steller's sea cow was a nine-metre marine mammal of the Bering Sea, discovered by Europeans in 1741 and hunted to extinction by 1768 — just 27 years, the shortest interval between scientific description and extinction of any large animal.
Updated 25 July 2026
- Length
- Up to about 9 m
- Weight
- Estimated 8–10 tonnes
- Closest living relatives
- Dugong and manatees (order Sirenia)
- Diet
- Kelp — an obligate marine herbivore
- Described by science
- 1741, by Georg Wilhelm Steller
- Extinct
- 1768 — 27 years later
Steller's sea cow holds a record no species should: 27 years from formal scientific description to extinction. It was an enormous, slow, docile relative of the manatee and dugong, up to nine metres long and possibly ten tonnes, grazing kelp in the frigid shallows of the Commander Islands. Georg Steller described it in 1741 while shipwrecked on Bering Island. Fur-trade crews working the North Pacific used the animals as a convenient meat supply, and by 1768 there were none. The population Steller found was already a tiny relict — a few thousand animals — which is why it took so little to finish.
Key facts at a glance
- Steller's sea cow was the largest member of the order Sirenia ever recorded — up to 9 m long and possibly 10 tonnes, dwarfing living manatees and dugongs.
- It went extinct in 1768, only 27 years after Georg Steller described it in 1741 — the shortest documented gap between scientific description and extinction for any large animal.
- It could not submerge fully and grazed kelp at the surface, which made it trivially easy to harpoon from a boat.
- The population Steller encountered was already a relict of a few thousand animals confined to the Commander Islands; the species had once ranged across the North Pacific rim.
- Steller observed the animals defending an injured companion, returning repeatedly to a harpooned individual — behaviour that made systematic hunting more efficient rather than less.
- Sea otter hunting in the same period removed the predators that control sea urchins, and urchin grazing degrades kelp forest — so the fur trade attacked the sea cow's food supply at the same time as the sea cow.
How was a species eliminated in 27 years?
Because there were very few left when Europeans found it, and because it was almost impossible to miss. By 1741 Steller's sea cow survived only around the uninhabited Commander Islands, a relict population of a few thousand animals. Fossil evidence shows the species once ranged widely around the North Pacific rim; earlier human hunting had already reduced it to that final refuge. The animals were enormous, slow, unafraid, and unable to dive — they grazed kelp at the surface in shallow water within easy reach of a boat. Russian fur-trade expeditions working the Aleutian and Commander chain found them an ideal provisioning stop: one animal yielded enormous quantities of meat and fat that kept well. Steller also recorded that injured animals were attended by others, which made repeat kills easier. Crews took far more than they used, wounding animals that drifted away and died. A population of a few thousand large, slow-breeding mammals cannot absorb that for three decades.
The kelp forest connection
The sea cow's extinction is a textbook trophic cascade, and it is why the species appears in ecology courses rather than only in extinction lists. Sea otters eat sea urchins. Sea urchins eat kelp. When the Russian fur trade removed sea otters from the North Pacific on an industrial scale, urchin populations expanded and grazed kelp forests down to bare rock — a state marine ecologists call an urchin barren. Steller's sea cow was an obligate kelp grazer. So at the same time as crews were killing sea cows directly, the trade in a different species was destroying the only food the sea cow ate. This is the mechanism that makes single-species conservation insufficient: the fur trade never targeted sea cows as an industry, but it removed their food supply as a side effect, and the two pressures together closed the window in under thirty years.
Where it lived
Commander Islands, Bering Sea
What caused it
- 1 Hunting by fur-trade crews for meat as ship provisions
- 2 A tiny relict population with no reserve capacity
- 3 Loss of kelp forest food supply as sea otters were hunted out
What this extinction teaches
A species can be destroyed by a trade that never targets it, through the food web. Protecting one animal while removing the species it depends on is not protection — which is why modern marine conservation works on whole systems, from kelp forests to coral reefs, rather than on charismatic animals alone.
Still here — for now
Still facing the same pressure: Dugong
Steller's sea cow's closest surviving relative, and an obligate seagrass grazer facing exactly the analogous problem: its food meadows are being lost to coastal development, dredging, boat scarring and warming seas. Some regional dugong populations are already listed as Critically Endangered.
IUCN status: Vulnerable
Did you know
Steller wrote the only scientific account of the living animal while shipwrecked on Bering Island during the winter of 1741–42, and the crew survived partly by eating the species he was describing — the sole eyewitness record of a species is also, in part, a record of eating it.
Steller's sea cow: frequently asked questions
When did Steller's sea cow go extinct?
How big was Steller's sea cow?
What killed Steller's sea cow?
What are its closest living relatives?
Could it still survive somewhere?
Sources
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