New research by Peter Godfrey-Smith, with David Scheel, a biologist at Alaska Pacific University, and Matthew Lawrence, an Australian diver, on octopus communication by bodily signals was recently featured in the New York Times, National Geographic, New Scientist, and NPR. Below are those three articles and the NPR podcast link, as well as a first-person account of the research process, from Godfrey-Smith’s blog, Metazoan.
Some animals just aren’t that social. Like octopuses. They don’t live in groups. They don’t have big chatterfests like prairie dogs. They don’t write, they don’t call.
But new evidence shows that an octopus may signal its intentions when it is about to whomp another octopus.
David Scheel, a biologist at Alaska Pacific University; Peter Godfrey-Smith, a philosopher of science who has appointments at City University of New York and the University of Sydney; and Matthew Lawrence, an Australian diver, collaborated to record interactions between common Sydney octopuses off the Australian island of Tasmania.
Their method was to put cameras on the sea floor in areas where there were plenty of these octopuses and then comb through hours and hours of video.
They aren’t done yet, but Dr. Scheel presented some of their initial findings in Anchorage at the annual meeting last month of the Animal Behavior Society, and they have about two dozen examples of octopuses signaling their aggressive intent.
He showed video of one octopus moving swiftly toward another as it made itself look taller and turned very dark. Octopuses have a remarkable ability to change their coloration to blend in with their surroundings, like chameleons. But this color change is the opposite. A darkened octopus stands out against a sandy bottom like an avenging cephalopod.
Dr. Scheel said there were hints in previous octopus studies of postures and behaviors like the ones he and his colleagues recorded. But there is very little evidence of any signals between octopuses.
He said that he and his colleagues had documented a number of signals of aggression — standing tall by rising up on the tentacles, turning dark, climbing onto higher (underwater) ground, spreading its tentacles and raising its mantle, which is the main part of an octopus body.
Most of the interactions don’t culminate in an actual struggle. Dr. Scheel said that although they were still analyzing the video, the signals seem to say: “I’m this big. I’m this tall. And I’m certain that I’m not going to back down.”
But that signal could be a way of avoiding a fight. The target octopus could read the signals and decide that keeping his spot on a pile of shells is just not worth it.
How many of the signals occur seemed to depend on how intense the encounter is. If all are displayed, then a fight is about to happen.
But sometimes, two octopuses just grow dark, slap tentacles and then settle down where they are. Perhaps it’s an octopus treaty, with both sides laying down their many arms.
The gloomy octopus of Australia sends cues to its rivals about whether it will flee or fight—a novel discovery.
Standing tall, arms spread, changing colors—them’s fighting words for an octopus.
Until recently, scientists thought the ocean dwellers didn’t communicate with one another much at all. Rather than sending signals with their skin color and texture, octopuses—mostly solitary, except during mating—were thought to camouflage themselves with it.
But new video evidence suggests at least one kind of octopus—the common Sydney octopus (Octopus tetricus)—sends cues to its rivals about whether it will flee or flight. (Also see “Social Octopus Species Shatters Beliefs About Ocean Dwellers.”)
David Scheel, a marine biologist at Alaska Pacific University, and colleagues shot the footage off southeastern Australia—the first evidence that fighting octopuses broadcast their intentions to one another.
Living to Fight Another Day
The common Sydney octopus, also known as the gloomy octopus, were thought to be very independent: When they do come together to mate, the female often eats the male afterward.
So the researchers were surprised that Sydney octopuses at their research site seemed to be interacting regularly.
“The expectation has been that if two octopuses meet, the big one eats the smaller one,” says Scheel, who presented the initial findings at a recent Animal Behavior Society meeting in Anchorage, Alaska.
“But if octopuses encounter each other routinely, they can’t cannibalize each other all the time.”
Instead, it makes sense that the octopuses would need to communicate to either escalate or avoid conflict—which is exactly what the team found. (See “Journey of Octopus Discovery Reveals Them to Be Playful, Curious, Smart.”)
Scheel and his colleagues observed a range of aggressive interactions between octopuses—everything from simply reaching out toward another octopus, to chases, to grappling. Of all these incidents, only a fraction were full-blown fights.
To get their point across, octopuses used a suite of dramatic behaviors such as spreading their arms wide, standing tall, raising their mantles—a structure that holds all their organs—like a crest above their eyes, and climbing on top of objects, the team observed. (See beautiful octopus pictures.)
The animals also changed color depending on their behavior: Aggressive octopuses tended to become darker, while fleeing octopuses were much paler.
“If one octopus signals that he’s coming over and not going to back down, and the other signals he is going to run away, that can end the interaction,” says Scheel.
“Whereas if they both signal that they’re not going to back down, those are the [incidents] that tend to escalate.”
This octopus body language likely occurs in more species, says Christine Huffard, a senior research technician at the Monterey Bay Aquarium Research Institute who was not involved in the new research.
“I would love to see people study this in different octopus species in the wild, but also research the mechanisms behind it,” Huffard says. “It’s hard to know whether it’s an intentional versus a physiological response. For instance, we blush. We don’t say, ‘Hey, body, tell this person I’m embarrassed.’ It’s just something that happens.” (“Watch: Stealthy Octopus Leaps From Water and Attacks Crab.”)
Huffard agrees with Scheel and his colleagues that it’s likely the octopuses are signaling to avoid costly battles.
When octopuses fight, the larger one nearly always wins.
“If you know from the beginning that you’re probably going to lose or you’re not really willing to give up an arm, you might as well tell your opponent that you don’t want a fight.”
Octopuses have been recorded gathering up armfuls of debris – and remember, they have eight arms – before taking pot shots at one another. Whether it’s a case of “get off my turf” or merely “oops, didn’t mean to hit you” is still a puzzle.
Octopuses have siphons on the side of their body, which they normally use for jet propulsion – they expel water forcefully through them, shooting forward as a result.
Gloomy octopuses (Octopus tetricus) living on a bed of shells at Jervis Bay, Australia, seem to have co-opted this system to throw things at each other in what may be the first use of projectile weapons seen in octopuses.
“Very few animals have been reported to throw things at one another, so it would be significant if the octopuses are doing it”, says Peter Godfrey-Smith, a marine biologist at the Graduate Center, City University of New York, who presented video evidence at the Behaviour2015 conference in Cairns, Australia, this month.
The technique the gloomy octopus uses seems to be a throw helped with a spit (see video above).
“In the ‘throwing’ behaviour, it gathers up a pile of stuff in its arms, and then directs the jet under the web of its arms, and throws out all the stuff under pressure,” says Godfrey-Smith. “So it’s a throw rather than a spit, though the throw uses water pressure – it uses a sort of inverted jet propulsion.”
Godfrey-Smith is not yet certain that the behaviour is intentional. It may just be a case of enthusiastic housekeeping showering the neighbours with debris.
“Octopuses often clean out their homes with a jet of water, pushing out sand and rubble. They also jet at intruders like pesky fishes,” says Jennifer Mather, a behavioural ecologist from the University of Lethbridge in Alberta, Canada, who was not involved in the study.
However, other octopuses were hit with the debris more often than you would expect by chance.
If indeed it is intentional, it may have evolved as a response to unusually crowded conditions at Jervis Bay.
The octopuses live on a midden made of shells, where they excavate dens. But with each octopus only having an area around a meter square to themselves, their neighbours can be as close as 30 centimetres away.
This is not the ideal living arrangement for solitary octopuses. But they probably put up with it because of overabundance of scallops – their favourite food – and a lack of other suitable nesting sites.
Even without the throwing behaviour, the crowding has brought out the worst in the inhabitants, it seems. A large female-male pair was caught on camera, for example, fighting intermittently for almost 2.5 minutes. Another time, a large octopus bullied a smaller one into leaving its den.
The team also observed many episodes of “boxing”, where two octopuses probed rapidly at each other with their arms (Marine and Freshwater Behaviour and Physiology, DOI: 10.1080/10236244.2012.727617).
The photo (a video frame) shows one of the most vigorous fights between two octopuses I’ve seen. It was taken at Octopolis, a site at Jervis Bay, Australia, discovered by Matt Lawrence in 2009. We wrote a first report about the site in 2012. David Scheel then joined us on the project, and we published a second paper about it last year. Together with Stefan Linquist, we all spent several days watching the site, with the aid of the dive boat Ocean Trek, at the end of last month.
The aim of this trip was to gather a bigger and more systematic body of video data about the site. In the past we’ve often left GoPro cameras down there to film what the octopuses do when we’re not there. This time we had the cameras going constantly, during daylight hours, with some of them raised high on tripods.
The all-seeing video coverage reminded me of Jeremy Bentham, the 18th century political philosopher, and his design for a high-surveillance building to be used in prisons, (and, among other places, POOR-HOUSES, HOSPITALS, MAD-HOUSES, AND SCHOOLS) called the panopticon. Bentham’s design has the watcher in the middle, not on the periphery, and unlike many of Bentham’s intended panopticon residents, our surveilled octopuses are free to come and go from the site. They tend to stay, though; one of the things that made last month’s trip a success was the large number of octopuses in residence (usually around 7) and almost ceaseless interaction among them, especially due to an unusually active and aggressive male, the right-hand individual in the first photo, who fought, mated, patrolled, and corralled his companions so vigorously that we wondered how he kept it all up. We haven’t gone through much of the video yet, but he seemed to rarely stop to rest or eat.
The frame above shows him again on the right, and the video below shows him getting into two fights in the space of about 30 seconds (the second including the sequence from which the frame above was taken). These incidents are different from the one pictured at the top of the post. In the frame above he looks large in comparison to the other, but this is not an unusually large octopus for the site, and some of his adversaries looked about the same size. The second victim in the video below is one of the most beaten-up I’ve seen there, with several arms damaged either by other octopuses or one of the many predators our octopuses have to deal with.
The fights are certainly dramatic, but some of the most interesting behaviors we see are non-aggressive – or at least much more restrained – ones. There is a lot of low-level jostling and jousting, and when one octopus passes another there is often an exchange of arm-pokes. I have thought of these as “boxing,” but Stefan found himself calling them “high-fives” – the different terms have such different connotations for their role in octopus life. It might be that some are more in one category and some are in the other. This video (which does look like boxing) was included in the online supplement to our first paper about the site.
Other arm-pokes do seem to have a different flavor, though. It’s another behavior we’ll have to analyze in detail when we go through the video and write it all up.
Here’s a collage of photos of some of the vertebrates. From top left clockwise: Steven Taylor and Stefan on deck, then David, Stefan, and me, then Matt carrying down gear, then Matt and David preparing cameras.