Science, Tech & Environment

Is there such a thing as octopus sign language?

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An octopus displays pale color and stretches out one arm before it withdraws from an approaching octopus. The approaching octopus displays dark color, stands tall, and spreads its web and arms.

Credit:

David Scheel

The octopus has been said to be asocial, not interacting much with others of its kind. But Current Biology published new research recently that says 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.

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David Scheel, a professor of marine biology at Alaska Pacific University in Anchorage, Alaska, spends a lot of time studying the communication habits of octopuses. 

“They're kind of flashy, actually,” Scheel says.

One communication behavior he’s noticed is that sometimes an octopus will turn dark, stand up very tall, spread its arms and web very wide, and then raise its body sac up above its eyes. 

“We think that means, ‘I'm not going to back down. I'm big and I'm here. So watch out,' ” Scheel says.

There are other forms of communication as well. A common one that Scheel has observed involves a sort of handshake. When one octopus approaches another, it will often reach out an arm to the other octopus, and the other octopus will reciprocate by reaching its arm back. Sometimes they touch, but not always. 

“We don't really understand what that is yet,” Scheel says. 

Scheel and his colleagues believe they’ve found hints that there might be social interactions in at least 12 species of octopuses. Now they want to figure out how the octopuses’ sign language or signals function in different contexts. 

“We established that there is some signaling going on, but we didn't establish what kind of context it occurs in,” Scheel says. “We're going to look at their mating system, their forging behavior and try to understand what's the context in which this signaling is most common.”

While Scheel still has research to do, these findings are already surprising.

“We do tend to think of octopuses as solitary. If they're going to get together it's either for mating, or the big one's going to eat the little one,” Scheel says, “It's a surprising site that we're working at.”

This article is based on an interview that aired on PRI's Science Friday.