Images and video: Peter Godfrey-Smith. The University of Sydney.
An unusual site chanced upon in the tourist area of Jervis Bay in NSW prompted a collaboration spanning the United States and Australia. University of Sydney Professor Peter Godfrey-Smith from the Faculty of Science, who is also a Distinguished Professor of Philosophy, City University of New York, said the high density of octopuses at the site allowed researchers to uncover some mysteries of their communication.
The new research looked at signalling and displays the animals use when they deal with each other in various competitive contexts. “There’s a lot of pushing other animals around, kicking them out of the site, and sometimes vigorous fights,” Professor Godfrey-Smith said.
“We showed when octopuses change colour they are signalling their degree of aggression. Darker colours go with aggressive behaviours, and these are combined with other displays.”
The researchers were tipped off about the site by a diver who alerted an online community of people interested in cephalopods that he had seen something interesting. The researchers followed up, ultimately witnessing 186 octopus interactions and more than 500 actions.
The findings are published today in the journal Current Biology.
Co-author Professor David Scheel of Alaska Pacific University in the United States said as a result of these new observations, they discovered octopuses used body patterns and postures to signal to each other during disputes. “The postures and patterns can be quite flashy, such as standing very tall, raising the body mantle high above the eyes, and turning very dark.”
They also learned that when an octopus with a dark body colour approached another dark octopus, the interaction was more likely to escalate to grappling. When a dark octopus approached a paler one, the pastier octopus more often retreated. When the opposite happened and a light octopus approached a darker one, the latter more often stood its ground.
“Dark colour appears to be associated with aggression, while paler colours accompany retreat,” Professor Scheel said.
Octopuses also displayed on high ground, standing with their web spread and their mantle elevated. Octopuses in that ‘stand tall’ posture frequently also sought higher ground. The researchers suspect the octopuses’ behaviours are meant to make them appear larger and more conspicuous.
The findings expand scientists’ understanding of how octopuses interact and communicate with each other. The researchers now suspect that social interactions among octopuses are likely to occur wherever food is plentiful and hiding places are scarce.
They will continue to study these octopuses and explore what role these signaling behaviors and other interactions play in their lives.
Published originally by The University of Sydney.