Just when you thought octopuses couldn’t get any more fascinating, they do!
A paper published on January 28th, 2016 in the journal Current Biology found that there is more to octopuses changing colors than camouflage or anti-predator behavior. Using close to 53 hours of recorded video and 186 interactions in a heavily octopus-populated area off in the waters of Australia, the scientists found that some displays of colors are signals that actually mediate combative interactions with one another.
(Octopus in foreground turn pales when retreating from confrontation with another octopus, seen standing tall and menacing in the background. Photo by David Scheel)
This is the first study to document the use of signals during aggressive interactions among octopuses.
David Scheel recalls for NPR the first time he observed this behavior: “I took a look fairly early on at one sequence in which one octopus approaches another in a fairly menacing way. He gets all dark, stands up very tall, and the other octopus crouches down and turns very pale. And then, when the approaching octopus persists, the other one flees. And this is immediately followed by the first octopus approaching a third octopus that’s nearby. And the third octopus turns dark and doesn’t crouch down. He just stays where he is, holds his ground.”
Excerpts from the paper:
Interactions in which dark body color by an approaching octopus was matched by similar color in
the reacting octopus were more likely to escalate to
grappling.
Darkness in an approaching octopus
met by paler color in the reacting octopus accompanied retreat of the paler octopus. Octopuses also dis-
played on high ground and stood with spread web
and elevated mantle, often producing these behaviors in combinations.
(Source: Scheel et al. 2016)
“[An aggressive] octopus will turn very dark, stand in a way that accentuates its size and it will often seek to stand on a higher spot,” explained Professor Godfrey-Smith to the BBC.
The scientists in this research actually dubbed the pose “Nosferatu” because the spread of the octopus’s web was reminiscent of a vampire’s cape, and they looked like Dracula was approaching his prey.
In the end, the color displays ultimately are correlated with the outcome of the interaction.
(Source: Scheel et al. 2016)
Scientists don’t exactly know why octopuses engaged in such heated and feisty exchanges. “It could be an attempt by one or more animals to control territory, as we saw males excluding males but not females, but this isn’t always the case,” Professor Godfrey-Smith said.
It had been previously thought that octopuses were mostly solitary creatures, and changes to body color and shape were viewed as tactics to avoid predators or to hide. This study however not only shows a very interesting range of behavior, but also may indicate complex social signaling.
Octopuses actually have a pretty exciting and dramatic social life after all.
The video above shows a dark-colored octopus, standing in the Nosferatu pose before attacking another dark-colored octopus, which eventually turns white and retreats.
