The friendly alien of the deep

Once regarded as a malevolent sea monster, the octopus is in fact a gentle, inquisitive and highly intelligent animal. Amia Srinivasan considers the “unboundaried potential” of this evolutionary curiosity

The octopus threatens boundaries. Its body, a boneless mass of soft tissue, has no fixed shape. Even large octopuses – the largest species, the Giant Pacific, has an arm span of more than six metres – can fit through an opening an inch wide, or about the size of its eye. This, combined with their considerable strength – a mature male Giant Pacific can lift 30lbs with each of its 1,600 suckers – means that octopuses are difficult to keep in captivity. Many octopuses have escaped their aquarium tanks through small holes; some have been known to lift the lid off their tank, making their way, sometimes across stretches of dry floor, to a nearby tank for a snack, or to the nearest drain, and maybe from there home to the sea. Octopuses do not have any stable colour or texture, changing at will to match their surroundings: a camouflaged octopus can be invisible from just a few feet away. Like humans, they have centralised nervous systems, but in their case, there is no clear brain-body distinction. An octopus’s neurons are dispersed throughout its body, and two-thirds of them are in its arms. (Octopuses have arms, not tentacles: tentacles have suckers only at their tips. Squid and cuttlefish have a combination of arms and tentacles.)

In evolutionary terms, the intelligence of octopuses is an anomaly. The last common ancestor between octopuses and humans was probably a primitive, blind worm-like creature that existed six hundred million years ago. Other creatures that are so evolutionarily distant from humans – lobsters, snails, slugs, clams – rate pretty low on the cognitive scale. But octopuses – and to some extent their cephalopod cousins, cuttlefish and squid – frustrate the neat division between clever vertebrates and simple-minded invertebrates. They are sophisticated problem-solvers; they learn, and can use tools; and they show a capacity for mimicry, deception and, some think, humour. Their intelligence is like ours, and utterly unlike ours. Octopuses are the closest we can come, on Earth, to knowing what it might be like to encounter intelligent aliens. Peter Godfrey-smith is a philosopher and diver who has been studying octopuses and other cephalopods in the wild, mostly off the coast of his native Sydney, for years. The alienness of octopuses, in his view, provides an opportunity to reflect on the nature of cognition and consciousness without simply projecting from the human example.

An octopus is an eight-armed, soft-bodied mollusc. Its arms are covered in suckers and arranged radially around a sharp-beaked mouth. It eats by catching prey with one of its arms and moving it through a conveyer belt of undulating suckers to its mouth – in that sense an octopus’s arms can also be thought of as its lips. On

top of its arms rests its head, which contains its brain and features two large eyes with horizontal, dash-shaped pupils, like a cat’s eyes turned on their side. Behind the head is the octopus’s mantle, a bulbous structure that contains its vital organs, including three hearts which pump blue-green blood. A tubular siphon is attached to the mantle, which the octopus uses variously for jet propulsion, respiration, excretion and inking predators.

Linnaeus called the octopus a singulare monstrum, “a unique monster”. Victor Hugo’s Toilers of the Sea includes a long description of the octopus, or “devil-fish”: “This irregular mass advances slowly towards you. Suddenly it opens, and eight radii issue abruptly from around a face with two eyes. These radii are alive: their undulation is like lambent flames… A terrible expansion!… A glutinous mass, endowed with a malignant will, what can be more horrible?” Octopuses are indeed glutinous; according to Sy Montgomery, author of The Soul of an Octopus, the slime on an octopus’s skin feels like a cross between drool and snot. But the octopus’s will is far from malignant, at least when it comes to humans.

Octopuses do occasionally attack people, giving a venomous nip or stealing an underwater camera when threatened or annoyed, but in general they are gentle, inquisitive creatures. (Fishermen, by contrast, often kill octopuses by biting out their brains, and in many countries they are eaten alive.) Octopuses encountering divers in the wild will often meet them with a probing arm or two, and sometimes lead them by the hand on a neighbourhood tour. Aristotle, mistaking curiosity for a lack of intelligence, called the octopus a “stupid creature” because of its willingness to approach an extended human hand. Octopuses can recognise individual humans, and will respond differently to different people, greeting some with a caress of the arms, spraying others with their siphons. This is striking behaviour in an animal whose natural life cycle is deeply antisocial. Octopuses live solitary lives in single dens and die soon after their young hatch. Many male octopuses, to avoid being eaten during mating, will keep their bodies as far removed from the female as possible, extending a single arm with a sperm packet towards her siphon, a manoeuvre known as “the reach”.

Just how clever are octopuses? An octopus has half a billion neurons, about as many as a dog. (A human has a hundred billion neurons.) In the lab, octopuses do fairly well: they can navigate mazes, use memory to solve simple puzzles and unscrew jars and child-proof bottles to get food. Yet it can take them a surprisingly long time to be trained in new behaviours, which some

“Octopuses encountering divers in the wild will sometimes take them by the hand and lead them on a neighbourhood tour”

researchers have taken as a sign of their cognitive limitations. In 1959, Peter Dews, a Harvard scientist, trained three octopuses to pull a lever to obtain a chunk of sardine. Two of the octopuses, Albert and Bertram, pulled the lever in a “reasonably consistent” manner. But the third, Charles, would anchor his arms on the side of the tank and apply great force to the lever, eventually breaking it and bringing the experiment to a premature end. Dews also reported that Charles repeatedly pulled a lamp into his tank, and that he “had a high tendency to direct jets of water out of the tank; specifically… in the direction of the experimenter”. “This behaviour,” Dews wrote, “interfered materially with the smooth conduct of the experiments, and is… clearly incompatible with lever-pulling.” Godfrey-smith says this “encapsulates much of the story with octopus behaviour”. Octopuses have a high curiosity drive, and a knack for repurposing things for their own ends. Perhaps there are tasks that octopuses find it hard to learn. Or perhaps they just have better things to do.

Captive octopuses appear to be aware of their captivity; they adapt to it but also resist it. When they try to escape, which is often, they tend to wait for a moment they aren’t being watched. Octopuses have flooded laboratories by deliberately plugging valves in their tanks with their arms. At the University of Otago, an octopus short-circuited the electricity supply – by shooting jets of water at the aquarium lightbulbs – so often that it had to be released back into the wild. The third-century Roman rhetorician Claudius Aelianus, a more sympathetic observer than Aristotle, identified the octopus’s main characteristic as “mischief and craft”.

Octopuses almost certainly feel pain. They nurse and protect injured body parts, and don’t like to be touched near wounds. They have sophisticated sensory capacities: excellent eyesight, and acute senses of taste and smell. But the question of what it might feel like to be an octopus is complicated by the odd relationship between its brain and its body. An octopus’s arms have more neurons than its brain, about 10,000 neurons per sucker. The arms can taste and smell, exhibit short-term memory, and perhaps see: researchers recently discovered that octopuses have the photoreceptors required for sight in their skin. Each arm acts with considerable independence from the brain; even a surgically detached arm can reach and grasp, avoid painful stimuli and change colour. Yet an octopus’s brain can exert executive control, “pulling itself together” when it needs to, for example when an octopus puts out a single inquisitive arm to inspect a stranger.

A further oddity is the creature’s relationship to colour. An octopus’s skin is a layered screen of pixel-like sacs of colour called chromatophores, which make it possible for an octopus to change its colour at will to match its surroundings or threaten an aggressor. The so-called mimic octopus can impersonate more than 15 different animals, including flounder, lionfish and sea snakes. An octopus’s colour also seems to indicate its mood – some octopuses turn white after being caressed for a long time by humans, as well as after mating. The chromatic displays produced by octopuses can include elaborate patterns of stripes and spots, flashing rings and waves of rippling colour. Yet octopuses – like most cephalopods – appear to be colour-blind. Their eyes (and skin) lack the variety of photoreceptors required to see colour, and octopuses are unable to distinguish between different coloured objects in experimental tests. Sometimes octopuses produce elaborate colour displays for no apparent reason, in the absence of predators or other octopuses. Do they talk to themselves? The problem with this thought is that octopuses appear not to have any language at all, and so presumably can no more talk to themselves than to others. The megapixel screen of the octopus’s body means that, theoretically, it could telegraph information of almost infinite complexity – the sort of expressive bandwidth of which a chimp or baboon can only dream. Yet most of the chromatic signals produced by an octopus appear not to have any consistent effect on other octopuses, suggesting that they are signs without meaning, words with no sense.

Most species of octopus live for only a year or two; the Giant Pacific, the species that lives longest, dies after four years at most. Both female and male octopuses mate only once, and enter a swift and sudden decline soon after, developing white lesions on their skin, losing interest in food, and becoming uncoordinated and confused. The females die from starvation while they tend their eggs, and the males are typically preyed on as they wander the ocean aimlessly. In its early evolutionary history, the octopus gave up its protective, molluscan shell in order to embrace a life of unboundaried potential. But an animal with a soft body and no shell cannot expect to live long.

Earlier this year, on a drive from San Francisco to Los Angeles, I went to see the two Giant Pacific octopuses at the Monterey Bay Aquarium. This was my second encounter with a live octopus. (I have had more encounters with dead octopuses than I care to recall. They make excellent carpaccio. Never again.) The first was off a beach in Mykonos, where I was snorkelling. There wasn’t much on the sea floor, just small crustaceans and darting silverfish, until I saw a red mass a few feet away, about the size of a cat, watching me with a single eye. I stayed still, watching it back. The octopus made small, unhurried movements, curling and uncurling its arms, snuffling along the floor. Eventually it crawled to a sunken rope some feet away and wrapped itself around it. Its body became a brown, barnacled coil, and then there was only a single white eye with a black dash of pupil. The eye closed, and the octopus vanished.

At Monterey the two Giant Pacifics were in adjacent tanks, each a few metres wide. The first octopus was energetic, unfurling its huge body and then compressing it, boiling and jetting its way back and forth through the water. When you’re looking at an octopus, your attention is naturally drawn to its rows of suckers, coiling arms and bulging body. Its eyes look sleepy, half-closed. You have to know what you’re looking for to see that they are open, and staring straight at you. I looked the octopus in the eyes and found it looking back at me, fixedly, as its body ballooned and hollowed behind it. The second octopus was quieter, bundled up at the top of her tank. A few thin strands of translucent, pearl-shaped eggs – laid and then painstakingly braided together with the thin tips of her arms – hung nearby, remnants of the clutch that had been removed by the aquarium keepers. Her skin was dull and white. She was dying. The logic of aquariums is the logic of conservation: individual animals must sacrifice their freedom so that the species as a whole can be protected. Yet ethical questions remain, raised by creatures, like the octopus, which so clearly yearn for freedom. Perhaps from our perspective the life of a wild octopus is already a tragic thing: sociality without society, speaking without being heard, a life-world without longevity. An alien. If only the octopus were more like us, we might be better at leaving it alone.

A longer version of this article first appeared in the London Review of Books.

“An octopus’s arm has more neurons than its brain. It can taste and smell, exhibit short-term memory and perhaps even see”