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One morning, while diving in a kelp forest off the coast of South Africa, Craig Foster noticed an unusual structure: a mound of seashells artfully stuck together, as though someone’s beach house decor had washed out to sea. Suddenly, with a sound like clattering teacups, the shells tumbled apart and a maroon octopus shot out of their midst. Wrapping herself in a sheet of kelp, the octopus briefly studied Foster before jetting away behind a cloud of ink.
Enthralled by the octopus’s ingenuity, Foster, a filmmaker, decided to start visiting her every day. Over the following year, he documented her many remarkable behaviors: how she used shells and seaweed to defend herself from sharks, innovated new hunting strategies, regrew a limb after a serious injury, and eventually mated and cared for thousands of eggs. Foster’s daily observations became the basis for the 2020 Netflix Original My Octopus Teacher, which captivated audiences when it debuted and won an Academy Award for Best Documentary Feature, among numerous other honors.
Although the film offers a detailed portrait of a wild animal’s life, its true subject is not so much the octopus herself as her relationship with Foster. When Foster began following the octopus, she was wary, rarely allowing him to get close. After nearly a month of visitations, however, she stretched out one of her arms to meet his, moving liquidly along his skin, each of her independently mobile suckers touching and tasting his anatomy for the first time. As Foster suggests on-screen, the octopus appeared to gradually trust him, repeatedly exploring his limbs and even riding to the surface on his hand. In one of the film’s most memorable moments, the octopus voluntarily rests on Foster’s bare chest, one of her arms curling gently against his chin and cheek. “When you have that connection with that animal and have those experiences, it’s absolutely mind-blowing,” says Foster in voice-over. “There’s no greater feeling on Earth. The boundaries between her and I seemed to dissolve.”
On first viewing, it’s easy to perceive these interactions as a form of genuine companionship—an impression encouraged by lingering close-ups and swelling music. The apparent emotional connection between Foster and the octopus is precisely the aspect of the film that provoked such a strong response from audiences and critics. Upon further reflection, however, the true nature of their relationship becomes more ambiguous. Only one member of the pair speaks directly to the camera. Any conclusions about the octopus’s subjective experience are based entirely on interpretations of her often-enigmatic behavior. Maybe what looks to us like tenderness is mere curiosity or bemusement. Perhaps an ostensible embrace is actually a deflection. No doubt some people are extremely fond of octopuses, but can an octopus really be friends with a human?
It’s much easier to understand how humans form reciprocal bonds with other social vertebrates with which we share a great deal of biology, behavior, and evolutionary history. Like us, many vertebrates are hardwired to form a variety of alliances and long-term relationships essential for their well-being and survival: rodents, canines, cetaceans, corvids, and certain fish and reptiles, to name a few. In contrast, the octopus—a mollusk separated from vertebrates by more than 500 million years of independent evolution—has long been regarded as a reclusive and antisocial creature. It’s rare to see more than one adult octopus simultaneously in the wild. Presumably, octopuses seek each other out only when mating, after which they part ways. Chance encounters often result in mutual evasion, 16-armed brawls, or cannibalism. “There’s sort of a joke that when two octopuses meet, they either mate or one of them eats the other,” says David Scheel, an Alaska Pacific University ecologist and octopus expert.
In the past decade, however, considerable evidence has challenged the octopus’s reputation as a loner. Biologists now recognize that at least some octopus species appear to be much more social than previously thought. Researchers have published reports of octopuses gathering in large groups on the seafloor, sharing dens, using color and gesture to communicate, and forming cooperative hunting parties with fish. Laboratory experiments further suggest that octopuses remember and distinguish individuals and learn by observing each other. In parallel, divers, professional aquarists, and cephalopod enthusiasts are increasingly sharing stories of intense mutual curiosity, surprising interactions, and even what some call friendship between humans and octopuses.
Human perception of the octopus is, much like the creature itself, manifold and mercurial. Depending on the circumstances, we have portrayed them as monsters and marvels, aliens and appetizers. The fact that octopuses are now widely agreed to be sentient creatures of exceptional intelligence and adaptability urges us to seriously consider the possibility of reciprocal human-octopus companionship. Yet their exquisitely unfamiliar biology makes them particularly easy to misinterpret. The mystery of octopus behavior—their unexpected and perplexing interactions with each other and with us—complicates our efforts to categorize animals as strictly gregarious or asocial, and forces us to confront unsettling questions about our interspecies relationships. When we look at an animal, how much of what we see is the animal itself, and how much is a projection of our own psyche? Even in our most intimate associations with other creatures, how can we know that they feel for us what we feel for them?
Octopus ecology does not offer obvious reasons for camaraderie. Animals regarded as having the most intricate and dynamic social lives, such as wolves, chimpanzees, and dolphins, are typically long-lived species that form tight-knit family units and invest a lot of energy in raising a few offspring. Among invertebrates, a few especially prolific groups—such as ants, bees, and termites—have evolved elaborate and highly regulated social hierarchies in which vast numbers of specialized and mostly sterile workers cooperate for the greater good of the colony. Octopuses do not fit either of these models. Most species of octopus fend for themselves, lay hundreds to tens of thousands of eggs at a time, do not parent their young after they hatch, and have life spans of less than two years. Nevertheless, biologists and aquarists have observed habitual social behavior in a few octopus species and what seems to be a latent capacity for occasional social interaction in others.
Some of the earliest reports of octopus gregariousness appeared several decades ago. In the 1980s, Arcadio Rodaniche, a marine biologist at the Smithsonian Tropical Research Institute in Panama, claimed that the larger Pacific striped octopus gathered in groups of 30 to 40 on the seafloor. In most octopus species, females lay one batch of eggs, care for it alone, and die not long after. In stark contrast, Rodaniche explained, reproductive pairs of larger Pacific striped octopuses shared dens and food and repeatedly mated beak to beak, and females produced consecutive batches of eggs, brooding for up to eight months. These behaviors were so unusual that Rodaniche’s peers dismissed his reports and rejected a long manuscript he hoped to publish. More than 30 years later, however, new research has corroborated most of his original observations.
In 2012, Richard Ross, a senior biologist at the California Academy of Sciences, and Roy Caldwell, an invertebrate zoologist at the University of California, Berkeley, acquired a few larger Pacific striped octopuses from aquarium traders and studied them at their respective labs. Together, they confirmed that this octopus species, which still lacks a formal scientific name, is just as social as Rodaniche originally described, sharing dens and food for days at a time, successively mating beak to beak, and never showing any signs of cannibalism. In 2015, Ross and Caldwell published their findings, with Rodaniche as one of the coauthors, just five months before the latter passed away.
Although congregations of larger Pacific striped octopuses in the wild remain unconfirmed, researchers have documented other species forming lively communities. On a November morning in 2009, recreational scuba diver Matthew Lawrence dropped his boat’s anchor in the center of Jervis Bay off the southeast coast of Australia and plunged into the sea. Sixteen meters below the surface, he came across a midden of shells strewn across the sand, surrounded by beds of living scallops. In the middle of the midden stood a mound-like structure about 30 centimeters tall, encrusted with algae, sponges, and coral—perhaps some metal object that had been jettisoned many years ago. In and among the shells was not just one octopus, or a pair, but an entire assembly with at least eight members. Most of the octopuses had dug dens in the sand and shells; the largest occupied a coveted spot beside the central mound. Many were roaming the vicinity, flaring shades of orange, or stretching their arms to tap their neighbors. The biggest octopus even approached and touched Lawrence. He knew right away this place was special. In all his years of diving, he had never seen anything remotely like it.
After Lawrence posted photos and details of his discovery on TONMO, a forum for cephalopod enthusiasts, word eventually reached Peter Godfrey-Smith, a philosopher of science at the University of Sydney who has written extensively on octopus cognition. Since then, Lawrence, Godfrey-Smith, and several collaborating researchers have repeatedly visited the site, which became known as Octopolis, as well as a second similar site several hundred meters away named Octlantis. Both areas were continually inhabited by around a dozen Octopus tetricus, the gloomy octopus or common Sydney octopus, a moderately large species with white eyes, a rust-red underside, and numerous pickle-like bumps on mottled brown skin.
Gloomy octopuses may have initially occupied these sites because they offered both an abundance of food in the form of scallop beds and sporadic shelter, such as rocks and encrusted debris. The accumulating layers of empty shells discarded by the octopuses gradually provided additional protection—a new substrate with which they could shield themselves from the dolphins, sharks, seals, and other predators that stalked the surrounding waters. As more octopuses formed dens in these unique locations, they began to interact more frequently. Sometimes, the gloomy octopuses at Octopolis and Octlantis sit side by side, mate, or probe each other innocuously; other times they jostle and fight, evict one another from dens, or engage in a dialogue of dominance: dark colors and tall postures seem to be associated with aggression, whereas pale shades and blotchy patterns correlate with submissiveness.
In collaboration with David Scheel, Godfrey-Smith and Lawrence have collected reports of similar social behaviors in more than a dozen octopus species, ranging from mere tolerance of each other’s presence to dominance hierarchies, complex mating strategies, and communicative displays. At least one experiment suggests that octopuses are also capable of social learning. In a study published in 1992, one group of octopuses required an average of 17 to 22 training sessions to learn to choose a plastic ball of a certain color in exchange for a reward. When a different group of untrained octopuses watched their tutored peers correctly perform the task a mere four times, they chose the correct ball 70 to 86 percent of the time.
At this point, then, substantial evidence indicates that mating and cannibalism are far from the only outcomes of an octopus rendezvous. “They clearly have other ways of relating to each other,” says Scheel. “That doesn’t mean all octopuses everywhere are social all the time, but when you put them together they have the ability to form relationships and manage them in complex ways.”
Scientists have also recorded certain octopus species, such as the day octopus (Octopus cyanea), hunting cooperatively with coral reef fishes. Some fish perform an underwater headstand over cracks in rock and coral where small prey is hiding, flagging the spot for an octopus; when the octopus reaches into the gap, it sometimes catches a meal and sometimes flushes the prey into the open, where the sentinel fish can hunt it. These types of interactions are not without conflict and compromise, however. Eduardo Sampaio, a PhD candidate at the University of Lisbon in Portugal, and his colleagues recently recorded day octopuses off the coast of Israel “punching” their finned hunting partners. In some instances, Sampaio speculates, the octopuses may have been trying to sanction the fish for not contributing enough to the partnership, or to keep them at a distance in order to procure more food for themselves. “We usually think of the octopus as a grumpy, solitary animal, moving along the seafloor, hunting and doing all these cool things, but keeping to itself,” says Sampaio. “But at least in some cases they actually collaborate with the animals around them.”
My Octopus Teacher may be the most famous tale of human-octopus friendship in recent memory, but it’s certainly not the only one. Other people have had markedly similar encounters. In the spring of 2018, while working at a remote resort on a coral atoll off the coast of Belize, Elora Kooistra encountered an octopus she would come to call Egbert. On their first meeting, he was a quivering blob of nerve and muscle, not much larger than her hand, hiding inside a conch shell on the seafloor, his two bulbous eyes peering out at her. As a rule, Kooistra, an experienced scuba diving instructor, never interfered with wild animals. In this case, however, her curiosity about the creature before her, and the affection she immediately felt for it, were too strong to ignore. She offered the octopus a few scraps of fish, which he quickly accepted.
In the following weeks, Kooistra routinely visited Egbert. She usually found him in the same shallow area, about three meters from the shore, nestled in one of several empty seashells scattered among the algae and seagrass. Kooistra would wear a snorkel mask and weight belt and sit on the sandy seafloor near Egbert, filming their encounters with a GoPro and periodically returning to the surface to breathe. Over time, Egbert gained confidence around Kooistra. He began grabbing her fingers and pulling her toward his conch shell. Kooistra started bringing him snacks in a glass jar. With some help, he learned to remove the lid, but he initially seemed more interested in examining the jar and exploring Kooistra’s hands than in eating his prize.
One afternoon, Kooistra couldn’t find Egbert in any of his favorite shells or usual hangouts. After searching for a while, she spotted him near a small log fuzzy with algae. She dove down and sat a few feet away. Egbert jetted over to her, wrapped himself around her hand, and pulled toward the log. As she approached, he swam to the log and began pushing against it, nudging it slightly, but not enough to roll it over. Kooistra stuck out her finger and Egbert guided it toward the log, which she pushed gently out of place. As the log rolled, Egbert slipped liquidly beneath it, grabbing a sea snail from its underside. Though Kooistra couldn’t be sure, she had the distinct feeling that she had helped an octopus hunt.
Kooistra had seen all sorts of wondrous ocean creatures in her career, including numerous octopuses, which were usually aloof and elusive. Never had an octopus been as inquisitive and charismatic as this one. She was astonished. “It was definitely one of the coolest experiences I have ever had with another animal,” Kooistra says. “I felt kind of special that this octopus actually wanted to interact with me.”
Octopus sociability may reveal itself most frequently and explicitly in captivity, where octopuses are perpetually presented with novel situations and the opportunity for intimate interspecies interactions. Among professional aquarists, octopuses have a reputation as highly individualistic animals that require frequent mental stimulation, often enjoy physical contact, and strongly prefer some humans over others, squirting water at one person playfully, while soaking another in what seems like a rebuke. “The more time you spend with them, the more you see their personality and feel a connection,” says Bill Murphy, a senior aquarist at the New England Aquarium in Boston, Massachusetts, who has cared for more than a dozen octopuses. “They recognize different people and behave differently with them. When I splash the water, they come right over. Other volunteers they ignore, or back away after touching their hands.” In The Soul of an Octopus by Sy Montgomery, which includes many anecdotes about octopus behavior, Alexa Warburton, then a pre-veterinary student at Middlebury College in Vermont, describes her experience working in a small octopus lab: “Some were so friendly, Alexa said, ‘they would lift their arms out of the water like a dog jumps up to greet you’… One named Kermit liked Alexa to pet him, and seemed to snuggle into the caress ‘by raising his shoulders—even though he didn’t have shoulders.’”
In addition to professional aquarists and scientists, a small and passionate community of hobbyists keeps octopuses in home aquariums. Nancy King has raised several octopuses in her Dallas, Texas, living room. One, a California two-spot octopus (Octopus bimaculoides) named Ollie, was especially interactive. “When she was young, she would sit there camouflaged, hiding and doing nothing,” King says. “I would sit there and talk to her, sing a song or something—just be there. Soon, she got very used to me. When she saw me, she would come out and play. She liked to be petted. And she used to pull on her feeding stick the way my dog plays with a towel.” Ollie even learned to interpret King’s pointing to indicate the location of a crab or other treat. “She was very social with me,” King says. “She would study my eyes, study what I was doing. They are smarter than dogs in some ways. It was terribly sad when she died. I am surprised when I think of her more than my dachshund.”
Not all octopus experts and caretakers are convinced that octopuses qualify as social creatures, however. Connor Gibbons, cephalopod facilities manager at Columbia University and a former senior aquarist at the New York Aquarium, does not think “social” is the right way to describe them. “I would even be hesitant to use the word playful,” he says. “It’s more that they are inquisitive or exploratory, that they show more interest in certain objects over others. The way their bodies work is so cryptic and amazing. They have their main brain and, at the base of each arm, a kind of mini brain. It’s awesome watching each arm work and explore almost independently, trying to figure things out. I think there’s a tendency to anthropomorphize them too much—to give them too many mammalian and human traits and emotions. They are very smart animals that display a certain level of critical thinking, but at the end of the day, they are so fundamentally different from us.”
In the past decade, octopuses have become increasingly famous for their creativity and cunning—traits not usually associated with other invertebrates, such as snails, worms, and flies. Octopuses can solve puzzles, use tools, deceive others, adapt their behavior to unfamiliar situations, communicate through pattern and posture, and, it seems, form impromptu social bonds with each other and other species. No other invertebrate demonstrates such extraordinary intelligence and behavioral flexibility. Where exactly did all this intellect come from?
Five hundred million years ago, the octopus’s Cambrian ancestors—armored mollusks akin to snails—oozed along the seafloor. Over time, some of them forfeited their shells in exchange for greatly enhanced agility and shapeshifting. The price of this freedom was vulnerability: tender and toothless, an octopus in open water is an easy meal for many predators. This liability, along with the demands of foraging, may have pressured octopuses to evolve bigger brains and greater intelligence—to outwit those they could not outrace or overpower. Whereas a typical mollusk, such as a slug or snail, might have anywhere from 4,000 to 50,000 neurons, the octopus has 500 million: 150 million in its brain and another 350 million in its arms, each of which contains organized clusters of neurons and is capable of independent decision-making. In terms of cellular processing power, octopuses are on par with some rodents, canids, and other mammals. The octopus is essentially a marine snail that evolved the brainpower of a raccoon.
A big brain is only part of the story, though. Every living creature is an alchemy of biology, environment, experience, and chance. The challenges of the octopus’s habitat, combined with the constraints of its anatomy, shaped its raw intelligence over millions of years. It became more curious and improvisational. It gained a stronger sense of self. It learned to discriminate between prey and predator, between the threatening, the benign, and the beneficial. These traits, which originally evolved in service of survival and reproduction, had profound and surprising consequences for octopus cognition and behavior. The average octopus may not be overtly social most of the time, but serendipity and happenstance—the mass appeal of a sheltered scallop bed, the outstretched fingers of another sentient species—can unlock hidden abilities, awakening forms of kinship, collaboration, and perhaps even empathy never previously expressed.
Despite the undeniable intelligence of octopuses, and the growing evidence of their sociability, there is still the perpetual challenge of correctly interpreting their behavior—especially their behavior toward us. Octopus caretakers often emphasize that many octopuses voluntarily solicit touch, play, and companionship, even when there is no food or material reward involved. Presumably, if they did not want such interactions, they would not pursue them. But that does not erase the impossibility of knowing what another species experiences, nor does it diminish the evolutionary chasm between mammals and mollusks. When an octopus rests briefly on Craig Foster’s chest, what makes us so confident that it’s a sign of friendship? When Egbert pulls on Elora Kooistra’s finger, is he really inviting her to help? Perhaps what we perceive as affection is actually reflexive exploration by a creature whose senses of touch and taste far surpass our own. Maybe octopuses don’t regard us so much as friends or associates as giant, elaborate levers they can manipulate for their own benefit. Though we know much more about octopuses today than even a few decades ago, they retain an essential inscrutability. There is no Rosetta Stone for octopus language, if such a language even exists. There is no familiar countenance or shared repertoire of emotion to consult. Instead, we have only a makeshift semiotics—an exchange of uncertain gestures across what may well be an unbridgeable abyss.
Since 2008, part-time science teacher Elizabeth Nitz has cared for more than 30 octopuses at her home in Livonia, Michigan—mostly small, crepuscular species. “Having an octopus in my living room sometimes feels like having a toddler in a playpen,” she says. “We interact, we have fun. They might be a brat, or super friendly; sometimes you get one that’s kind of gloomy, or moody, or a show-off. But what keeps me coming back is the relationship you form—the fact that they are social.” Many of the octopuses Nitz has raised would routinely rouse and cling to the glass of their tank whenever Nitz and her family were eating dinner, watching TV, or otherwise interacting nearby. If the family moved to another part of the room, the octopus would shift her position to get a better view.
One of the first octopuses Nitz raised was an algae octopus (Abdopus aculeatus) she named the Once-ler after the narrator of The Lorax by Dr. Seuss. She and her daughters would stand in front of the Once-ler’s tank and wave their whole arms as though they were undulating blades of kelp. Eventually, the Once-ler started waving back, imitating their movements with a single arm while keeping all the others tucked neatly beneath her or stuck to the glass. It became a frequent ritual.
When the Once-ler started laying eggs, Nitz steeled herself for what would happen next. As female octopuses brood, they become sluggish and start to deteriorate, losing pigmentation and muscle tone and forming lesions that never heal. The Once-ler spent most of her time with half her body inside her den, guarding her eggs, occasionally extending an arm to probe a piece of food, though she eventually stopped eating altogether. One morning, Nitz woke up and found thousands of baby octopuses, each smaller than a grain of rice, bobbing and spinning through the tank. The Once-ler had torn apart her den to help her children swim free. Now, she was sprawled on the bottom of the tank, sickly pale, her mantle heaving with every labored breath. Nitz sat in front of the tank with her daughters, her hand on the glass, crying softly as their beloved octopus’s breathing became slower and heavier. Suddenly the Once-ler did something none of them expected in those last moments: she inhaled deeply, raised her arm, and waved. “I waited for more breaths, but there weren’t any,” Nitz recalls. Maybe that final gesture was merely a muscle spasm caused by short-circuiting neurons. Perhaps, in their grief, Nitz and her family were seeing what they wanted to see. Still, Nitz says, “it felt for all the world like she was waving goodbye.”