Twelve sea otter facts, fact-checked
The sea otter (Enhydra lutris) is the smallest marine mammal and one of the clearest examples of a keystone species. Full profile in our sea otter guide.
1. The densest fur of any animal
Up to a million hairs per square inch — the reason they were hunted almost to extinction.
2. No blubber
Unlike other marine mammals, sea otters rely entirely on fur for insulation, which is why oil contamination is lethal: fouled fur stops insulating.
3. They use tools
Rocks are used to crack shells against the chest, and many otters keep a favourite stone in a loose skin pouch under the foreleg.
4. They eat about a quarter of their body weight daily
Staying warm without blubber demands an enormous metabolic rate.
5. They are a keystone species
By eating sea urchins they prevent urchin barrens, allowing kelp forests to persist. Remove otters and the kelp goes with them.
6. Kelp forests store carbon
Because otters protect kelp, their presence has a measurable effect on carbon storage — a rare directly quantified link between one predator and climate.
7. They hold hands, or use kelp
Resting otters wrap themselves in kelp fronds to avoid drifting; holding paws in rafts is real but less common than the internet suggests.
8. Rafts can number in the hundreds
Groups of resting otters, usually segregated by sex.
9. Pups float from birth
Pup fur is so buoyant that a newborn cannot dive. Mothers wrap pups in kelp while they forage.
10. The fur trade nearly ended them
Hunting reduced a population of hundreds of thousands to around 1,000–2,000 animals before protection began in 1911.
11. Recovery has been partial
Numbers rebounded in places but remain far below historic levels, and the southern sea otter is still restricted to a fraction of its former range.
12. They are Endangered
Oil spills, entanglement, shark bite mortality and disease from land-based pollution all continue to constrain recovery.
Read the full sea otter wildlife guide for IUCN status, population context and sources — or donate to WARN to help fund the partner teams protecting wildlife on the ground.
