Twelve octopus facts, fact-checked
Octopuses are the closest thing on Earth to an intelligence that evolved along a completely separate path from ours. Full profile in our octopus guide.
1. Three hearts
Two branchial hearts pump blood through the gills; a third systemic heart drives it around the body. The systemic heart stops when the animal swims, which is part of why octopuses prefer to crawl.
2. Blue blood
Octopus blood carries oxygen using haemocyanin, which is copper-based rather than iron-based, so it is blue. Haemocyanin works better than haemoglobin in cold, low-oxygen water.
3. Nine brains, functionally
A central brain plus a large nerve cluster in each of the eight arms. Roughly two-thirds of the animal's neurons sit in the arms, which can execute complex actions semi-independently.
4. An arm keeps working when severed
Because of that distributed control, a detached arm continues to react to stimuli and can even pass food towards where the mouth would be.
5. They are colour-blind — and change colour
Octopus eyes have a single photoreceptor type. Current evidence suggests they may sense colour through light-sensitive proteins in the skin itself, effectively seeing with their body.
6. Skin changes texture as well as colour
Muscular papillae raise and flatten the skin to mimic sand, rock or seaweed, so camouflage is three-dimensional, not just a pattern.
7. Only the beak is hard
An octopus can squeeze through any gap its beak fits through — which for a large animal can be startlingly small.
8. Each sucker tastes
Suckers carry chemoreceptors, so an octopus tastes whatever it touches. It can identify prey inside a crevice it cannot see into.
9. They use tools
The veined octopus carries coconut shell halves to assemble as portable shelter — one of the clearest examples of tool use outside vertebrates.
10. Ink is more than a smokescreen
The cloud both obscures and contains compounds that interfere with a predator's sense of smell, buying escape time twice over.
11. Most live only one to two years
Short lives are the rule. Females typically stop feeding while guarding eggs and die soon after they hatch.
12. They are famous escape artists
Captive octopuses open jars, dismantle enclosures and exploit gaps — behaviour that says as much about their problem-solving as any laboratory test.
Read the full octopus wildlife guide for IUCN status, population context and sources — or donate to WARN to help fund the partner teams protecting wildlife on the ground.
