The underwater cameras got it all: The octopuses emerged from a cluttered bed of empty shells, arms unfurling like ribbons. Then, suddenly, a cloud of debris came spewing out from underneath their arms. Usually it was silt, which billowed through the water like smoke. Sometimes it was shells. Sometimes it hit another octopus.
The action unfolded dozens of times a day in the waters off the coast of Australia in 2015 and 2016. The participants were gloomy octopuses, so named likely because of their harrowed-looking eyes. A casual observer might assume that these funky-looking octopuses were duking it out, or engaging in play fighting, using silt instead of snowballs. After all, we humans tend to anthropomorphize animals, especially when they engage in behaviors that appear familiar to us. That tendency can be especially tempting with cephalopods—elusive, graceful-looking creatures known for their air of mystery and remarkable intelligence, which have taken on an almost mystical status in the public imagination. But there may be much less than meets the (sad-looking) eye in this particular set of underwater observations.
David Scheel, an ecologist at Alaska Pacific University, and his colleagues analyzed hours of the gloomy-octopus footage. Gloomy octopuses, the team concluded in research published today, threw stuff around quite deliberately, sometimes directing the debris at other nearby octopuses. “It seems like there’s a target, and they’re not throwing away; they’re throwing at,” Scheel told me. Such throwing behavior, the researchers say, has never been reported in octopuses before.
The flinging works like this: An octopus gathers debris with its arms and holds it close, then expels water through its siphon, a funnel-shaped structure that octopuses use to propel themselves through water, like an anatomical jetpack. The burst of water sends the debris flying. Half of the incidents that Scheel’s team recorded occurred when other octopuses were nearby. Octopuses whose skin temporarily darkened in color—a reaction associated with aggression—threw debris more forcefully, and were more likely to strike another animal. Some animals exhibited signs of what could be interpreted as aiming, releasing material from their sides rather than the front. And some octopuses in the line of fire seemed to react like any person would: They raised their arms toward the offending octopus, or simply ducked.
Several octopus researchers who were not involved with the work question whether the behavior actually counts as throwing. The siphon action is similar to “squeezing your chest muscles and blowing air out through your nose and mouth,” Robyn Crook, an evolutionary biologist at San Francisco State University, told me. Although scientists have observed octopuses passing and releasing material with their arms, they have not documented a concerted act of throwing in the way most of us understand the process: grasping something, recoiling an arm, extending that arm outward, and finally releasing the object. “A throw, to me, sounds like it should involve those types of movements in that type of sequence,” Crook said.
Siphon-directed pseudo-throwing actually happens all the time. Octopuses like to tidy their den, especially after a big meal, and they use this body part to do it. Perhaps they just happened to hit another octopus by accident; in the footage, just about 17 percent of “throws” hit others in the area. “It seems like most of the time, they’re just kind of randomly removing stuff from their surroundings,” Crook said. What looks intentional to one observer may seem accidental to another. “A lot of animal-behavior analysts would look at the same sequence of behavior and give a different interpretation,” Crook said.
Scheel and his team say the behavior is noteworthy because it appears in a social context—one octopus hitting another! But Jennifer Mather, a cephalopod expert at the University of Lethbridge, cautions against describing the interactions observed among these octopuses as social behavior. Octopuses are solitary creatures, yet we humans seem keen on believing they can live together in harmony. When divers discovered underwater settlements of gloomy octopuses in Australia, the popular press dubbed the locales “Octopolis” and “Octlantis.” But the animals were never attracted to one another, Mather told me. “This is a case of being attracted to a place to hide.” They simply came for the shelter of a shell-strewn spot in an otherwise empty, muddy expanse.
Even if the gloomy octopuses caught on film were trying to hit one another, their behavior might not be, strictly speaking, social. Scheel’s team also observed octopuses flinging debris at a nearby camera and some fish. Piero Amodio, a biologist who studies octopus behavior at Anton Dohrn Zoological Station, in Italy, thinks the shell-siphoning is likely “used more broadly, towards annoying or threatening stimuli,” octopus or not.
This uncertainty is not an octopus-specific problem. “It’s really hard to infer the motivation of animals,” Christian Nawroth, who studies the behavior of goats at the Research Institute for Farm Animal Biology, in Germany, told me. That’s especially true when you’re observing them in a natural habitat and not in a controlled environment, where you can adjust experimental conditions. Goats have their own mysteries. They sneeze when they’re spooked or frustrated, and “there is actually nothing on how often goats show this behavior, how often they use it, in which contexts they use it,” Nawroth said. Anecdotal reports suggest that some goats carry a branch around on their horns and use that to scratch parts of their body. Maybe it’s true tool usage, or maybe “the branch landed somehow or got stuck between the horns, and they now use it to scratch themselves just because they figured out that they can do this, and there’s no insight involved in using this as an actual tool,” Nawroth said. These are genuine mysteries of animal intelligence, yet none of them seem to capture our interest in quite the same way as similar behaviors in octopuses.
Octopus researchers know that their subjects are well loved. There is no shortage of popular-science books or documentaries about octopus consciousness, intelligence, and even souls, the accounts dipped with awe. (Scheel himself is writing a book subtitled The Mysteries of Octopuses.) When we’re not rendering octopuses as cute plush toys, we’re asking them to predict the outcomes of World Cup games (and believing that they’re good at it). “Lots of people find octopuses to be charismatic and interesting, and you do seem to see overinterpretation of behavior in cephalopods, where people tend to see extraordinary abilities where more a parsimonious explanation would probably suffice,” Crook said. Mather put it more simply: “Maybe it would be nice if octopuses weren’t sexy.”
Scheel said that he and his colleagues will continue looking for answers in the footage of gloomy octopuses. By now, the animals on the tape are long gone; like most octopuses, gloomies are thought to live for only a year or two, Scheel said. The researchers haven’t monitored the site recently, so they don’t know whether others have converged on it. They don’t know whether a new generation is spraying sand-coated shells around, maybe on purpose but maybe not, oblivious to the inscrutable creatures on land who really, really want to find out what’s going through their mind.