Eight Arms That Send a Message
The octopus has been said to be asocial, not interacting much with others of its kind. But new research published this week in the journal Current Biology says that at least one species of octopus uses its changing coloration and shifting postures to send clear signals to others of its species, particularly in times of potential conflict. David Scheel, a professor of marine biology at Alaska Pacific University in Anchorage, Alaska, pored over hundreds of hours of octopus video footage to document the signaling behavior.
David Scheel is a Professor of Marine Biology at Alaska Pacific University in Anchorage, Alaska.
IRA FLATOW: We here at Science Friday have a special affinity for cephalopods, in case you haven’t noticed, including my favorite the octopus. The octopus likes to live alone and has been able to be asocial, not interacting much with others of its kind. But new research published this week says that at least one species of octopus uses its special talents changing coloration and postures to send signals to other octopuses, sort of an octopus pantomime. David Scheel is professor of marine biology at Alaska Pacific University in Anchorage and one of the authors of a paper on the findings published this week in a journal, Current Biology. Welcome to Science Friday.
DAVID SCHEEL: Hello, Ira, thank you for having me on your show.
IRA FLATOW: You’re quite welcome. What do these signals look like?
DAVID SCHEEL: They’re kind of flashy actually. The octopuses turn dark, stand up very tall, spread their arms and web very wide, and then they raise their mantle, which is sort of the body sack behind the eyes, they raise that up above their eyes. And then sometimes they will even seek out high ground to do that display on top of from a high point.
IRA FLATOW: And what does that signal mean?
DAVID SCHEEL: Well, we think it means I’m not going to back down, I’m this big and I’m here so watch out.
IRA FLATOW: Are you surprised that they do this?
DAVID SCHEEL: Some of it’s surprising, yeah. As you mentioned, we do tend to think of octopuses as solitary. If they’re going to get together it’s either for mating or the big ones going to eat the little one. And it’s a surprising site that we’re working at because the octopuses co-exist there for some time.
IRA FLATOW: You know, humans do things that other people can see that may not have evolved to convey information like blushing and embarrassment, could this be just an involuntary reaction?
DAVID SCHEEL: Well, we did consider that possibility. And some of it possibly. But for example, the octopus that’s approaching and wants to hold its ground, that one turns dark and may give chase if the other one runs away. And the octopus that’s going to yield ground turns very pale, or puts on what we call a deimatic display, which is pale color with high contrast dark patches on it. And so now we have a chasing octopus whose dark and a fleeing octopus whose pale, and it’s hard to think of a physiological reason why chasing towards something would turn you dark and chasing away from something would turn pale. So it does seem like this is some sort of signal– communication.
IRA FLATOW: I’m Ira Flatow This is Science Friday from PRI, Public Radio International, talking with about octopuses with David Scheel. I mean, we’ve talked about octopuses, they are so unique. I mean in things that they can do, we have videos of them walking, we have videos of them in their camouflage. Is it possible that they could– sometimes they throw things I understand.
DAVID SCHEEL: Yeah, we have seen that at this site. We’re still working on that a little bit, yes. The thing about the octopus is they’re kind of the universal animal. They can do a little bit of everything it seems like.
IRA FLATOW: Can they fight off two different things at once? Can they make one side of their body get that dark side and one side remain pale at the same time?
DAVID SCHEEL: They do. We haven’t seen dark on one side and pale on the other, but what we have seen at this site is a retreating octopus will give the pale signal on the side of the body facing the approaching octopus, and on the other side of the body it will maintain a fairly neutral color that’s pretty close to the background in color intensity. It’s a bit like the zebra looking grey in the predators eyes. It maintains that gray color that probably from any distance at all matches it to the background.
IRA FLATOW: Now I know that you spent hours and hours watching octopuses, are there any signals you’re seeing that you don’t know what they mean yet?
DAVID SCHEEL: There is an interesting one that’s very common. When one octopus approaches often it will reach out an arm towards another octopus and then the other octopus may reach back towards the approaching octopus. And we don’t really know what this is. They don’t always touch. Sometimes they do. And very often that’s the extend of it. An octopus will walk across this area where we’re studying and three or four other octopuses will reach out an arm towards it and then withdraw the arm. And we don’t really understand what that is yet.
IRA FLATOW: Do they have like a favorite arm, like right handed or left handed? Is there one tentacle or arm that they use more than the other?
DAVID SCHEEL: They definitely are using their first left or right arm for this reaching behavior most commonly. There is a study that shows handedness in another species of octopus, but we haven’t looked at it at this site yet.
IRA FLATOW: And so what’s the next thing you would like to study?
DAVID SCHEEL: Oh, there’s not just one, Ira.
IRA FLATOW: I’ve only got two minutes.
DAVID SCHEEL: OK. So, I think the next step at this site is to try and look at how the signals function in different contexts. Right now we’ve established that there is some signaling going on but we did not establish what kind of context it occurs it and so maybe we’re going to look at their mating system, their foraging behavior and try to understand what’s the context in which the signaling is most common.
IRA FLATOW: We talked about them being isolated– they like to be loners– do they ever find them living in groups?
DAVID SCHEEL: They are here. And we think that’s because this is a little bit of shelter and a big sea of food. And so it’s a great place to hang out but in order to do so they have to tolerate each other. There are groups that have been found in another species of octopus and some displays occurring during mating in yet another. So in this paper we found that there are hints that there might be social interactions in at least 12 species of octopuses already in the literature.
IRA FLATOW: They’re certainly fascinating. As a scuba diver I’ve encountered them underwater and they’re just so interesting to just sit there and watch. Thank you Dr. Scheel for taking time to be with us today.
DAVID SCHEEL: Thank you very much.
IRA FLATOW: David Scheel, professor of marine biology at Alaska Pacific University in Anchorage, and he was one of the authors of a paper in current biology.