Common Octopus (Octopus vulgaris): Facts and Intelligence

What does a common octopus look like?

A common octopus has a rounded, baglike body called the mantle, which holds the gills, hearts, digestive organs and ink sac. In front of the mantle is the head with two large, prominent eyes, and from the head spread eight muscular arms, joined at their base by a short web of skin. Each arm carries two rows of suckers along its whole length. The mouth sits hidden in the center where the arms meet and is armed with a hard, curved beak much like a parrot’s.

Its color is never fixed. A resting octopus is often mottled brown, gray or reddish, but it can turn pale, dark, spotted or striped within moments. It can also raise small bumps and flaps called papillae, so smooth skin suddenly looks like a weedy rock.

The common octopus has no skeleton at all. Its only hard parts are the beak, the radula (a tongue-like ribbon of tiny teeth) and a capsule of cartilage around the brain. Inside, it has three hearts and copper-based blood that turns blue when it carries oxygen, explained in how many hearts does an octopus have?

How big is a common octopus?

Common octopuses are medium-sized for their family. Most adults caught by fisheries weigh under 3 kg (6.6 lb), but a few grow much larger.

The arms make up most of the length; each is several times as long as the mantle. Growth is remarkably fast for an invertebrate. In warm water, young octopuses can add several percent to their body weight every day, and many pass 1 kg (2.2 lb) within their first year. The largest octopus species of all, the giant Pacific octopus, is far bigger and lives in the cold North Pacific.

Habitat and range

The common octopus lives on the seabed in warm and temperate coastal waters, from tide pools down to about 200 m (660 ft), though most live shallower than 100 m (330 ft). It prefers rocky reefs full of cracks and holes, but also uses seagrass meadows and sandy or muddy bottoms, where it moves into empty shells, cans, bottles and old pottery.

In the strict sense, the species ranges through the Mediterranean Sea and the eastern Atlantic, from the southern coasts of England and the English Channel south along West Africa to South Africa, including the Azores, Canary Islands and Cape Verde Islands. It avoids water that is too fresh, so it is absent where rivers lower the salinity.

Common octopuses are not true migrants, but in some areas, such as the northwest Mediterranean, larger animals move inshore in spring to breed and retreat to deeper water in late summer and autumn.

One species or several?

For about two centuries, scientists treated look-alike octopuses from warm coasts around the world as one global species. Genetic studies since the 2000s have shown that O. vulgaris is really a species complex, a group of very similar species that are hard to tell apart by eye:

• The East Asian common octopus (Octopus sinensis) of Japan, China and Korea was confirmed as a separate species in 2016–2017.
• Octopus americanus of the western Atlantic, including the Caribbean, was redescribed in 2020.
• Octopus insularis, off Brazil and in the Caribbean region, was described in 2008.
• The gloomy octopus (Octopus tetricus) lives in eastern Australia and New Zealand, and Octopus djinda of Western Australia was named in 2021.

So an octopus seen by divers off Florida or Japan is probably not O. vulgaris in the strict sense. Older books and fishery statistics often still lump them together.

What do common octopuses eat?

The common octopus is a carnivore. It prefers crabs, lobsters and shrimp, along with clams, mussels, cockles and snails, and it also takes small fish and even other octopuses. It hunts mostly at dusk and at night, though in some places it forages by day.

It uses several techniques. It may pounce and trap prey under the web between its arms, or probe crevices with its arm tips, feeling and tasting for anything edible. To get into a shell it either pulls the two halves of a clam apart or drills a tiny hole with its salivary papilla, a small organ near the beak with minute teeth, and then injects venomous saliva that paralyzes the prey and loosens the muscle.

Prey is usually carried home to the den and eaten there. The empty shells and crab claws pile up outside as a midden, which tells divers and scientists exactly what the octopus has been eating.

Camouflage and defense

Camouflage is the common octopus’s first line of defense. Its skin holds thousands of color cells called chromatophores, tiny elastic sacs of yellow, orange, red, brown or black pigment, each opened and closed by muscles under direct nerve control. Beneath them, reflective cells called iridophores and leucophores add shimmer and white. Together with papillae and body posture, they let the octopus match rock, sand or algae within a fraction of a second.

Remarkably, the common octopus appears to be color-blind, with only one type of light-sensitive pigment in its eyes. How it still matches the colors of its background is not fully understood; light-sensitive proteins found in octopus skin may play a part. The species also flashes dark and pale patterns as a warning, and it can send dark bands rippling across its body, a display called the passing cloud. It is one of the best-known animals that change color.

If camouflage fails, it squirts a cloud of black ink made of melanin and mucus, then jets away by forcing water out of its funnel. An octopus that loses an arm to a predator can grow it back.

Intelligence and behavior

Common octopuses are solitary and spend much of the day in a den, a crack or hole that they sometimes barricade with stones and shells. They leave at dusk to hunt and return to the same den or move to a new one every few days. Neighbors keep their distance and meet mainly to mate.

The species has about 500 million neurons, roughly as many as a dog has in its cerebral cortex, and about two-thirds of them lie in the arms rather than the brain. In laboratory tests since the 1950s, common octopuses have learned to tell shapes, sizes and brightness apart, found their way through mazes and learned to remove the stopper from a glass jar to reach a crab inside. They also show behavior that looks like play, such as repeatedly pushing objects around a tank. Read more in how smart are octopuses?

Their abilities have earned them legal protection. From 1993 until 2012, the common octopus was the only invertebrate protected under the UK’s law on scientific experiments, and a 2010 European Union directive extended protection to all cephalopods used in research. Studies also suggest that common octopuses sleep, with a quiet state of rest from which they are harder to wake.

Reproduction and life cycle

Males have a specialized third right arm called the hectocotylus, with a groove and a spoon-shaped, suckerless tip. During mating, which can last hours, the male slips this arm into the female’s mantle and passes over packets of sperm. Both sexes may mate with several partners, and genetic tests have found eggs from one female fathered by more than one male.

The female then finds a sheltered den and lays 100,000–500,000 small eggs, which she glues in long strings to the roof of the den. She stays with them day and night, cleaning them with her arm tips, blowing fresh water over them and fending off intruders. She usually does not eat during this time, which lasts from about a month in warm water to four or five months in cold water.

The young hatch as tiny paralarvae that drift in the plankton for several weeks, eating small crustaceans, before they settle on the seabed and take up the adult way of life. Only a tiny fraction survive.

How long do common octopuses live?

Common octopuses usually live 12–24 months. Their lives end soon after breeding: males weaken within weeks or months of mating, and a brooding female dies shortly after her last eggs hatch, often having lost about a third of her weight. This programmed decline, called senescence, is controlled by the optic glands near the brain. The full story, including deep-sea octopuses that live much longer, is in how long do octopuses live?

Predators, fishing and conservation status

Common octopuses are eaten by moray and conger eels, groupers, sharks, dolphins, seals and seabirds, as well as by larger octopuses. People are also major predators. The species is one of the most valuable octopuses in commercial fisheries, with large catches off northwest Africa and in Spain, Portugal and the wider Mediterranean.

The IUCN Red List classifies the common octopus as Least Concern, in an assessment published in 2018. Because it grows fast and breeds in huge numbers, populations can recover quickly, but some stocks have been overfished and catches can swing sharply from year to year.

Plans for commercial octopus farming, including a proposed farm in Spain’s Canary Islands, have drawn strong criticism from scientists and animal welfare groups, who argue that intelligent, solitary predators are poorly suited to captivity. In 2024, Washington and California became the first US states to ban octopus farming.

Myths and facts

Myth: octopuses have tentacles. Biologists call all eight limbs arms. In cephalopods, tentacles are the two long feeding limbs that squid and cuttlefish have in addition to their arms. See octopus vs squid for the other differences.

Myth: an octopus has nine brains. It has one central brain, wrapped around its esophagus. Each arm has a thick nerve cord with many small clusters of nerve cells that control the arm and its suckers, but these are not separate brains.

Myth: octopuses attack divers. Common octopuses are curious and may reach out an arm to explore a diver’s hand, but they are not aggressive and usually hide or flee.

Fact: an octopus became a famous oracle. Paul, a common octopus at an aquarium in Oberhausen, Germany, was said to “predict” the winners of German matches at the 2010 FIFA World Cup by choosing food boxes marked with flags. His run of correct picks was luck, not foresight. The 2020 documentary My Octopus Teacher, which follows a wild octopus in a South African kelp forest, won the Academy Award for best documentary feature.