Study details coordinated three- and four-step sequences octopuses use to pass through narrow openings
Researchers observed common octopuses employing distinct multi-step movements to squeeze through holes smaller than their bodies, findings that could inform the design of flexible robots.
Scientists from the National University of Singapore, the University of Naples Federico II and Vienna’s Haus des Meeres-Aqua Terra Zoo recorded common octopuses navigating openings narrower than their bodies. Using clear acrylic partitions with a single gap, the team captured the animals from multiple angles and identified two recurring movement patterns – a three-step sequence for moderately sized holes and a four-step sequence for tighter passages.
In the three-step pattern, an octopus first probes the opening with one arm, then threads additional arms through before anchoring two arms on the far side to pull the remaining limbs, head and mantle through. When the hole is relatively smaller, the animals add a fourth stage: after the initial probing and arm-shifting, they transfer the remaining arms across the gap, rotate their bodies upward, and finally draw the head and mantle through.
"Octopuses can change their body shape to squeeze through tiny holes, almost like water flowing through a gap, so their size doesn’t always limit where they can go," said researcher Wenci Xin.
The experiments involved three subadult common octopuses, each tested with openings matched to the distance between its eyes – a proxy for the relatively rigid central nervous system. Across 33 trials, 30 successful passages were analyzed. A separate set of juvenile Mayan octopuses did not display the four-step maneuver in the smallest openings but could use the three-step sequence in larger gaps.
The authors note that the small sample size and testing each animal under only one hole-size condition limit the ability to separate strategy from individual variation. They also acknowledge that mantle deformation was not systematically measured, leaving part of the squeezing mechanics for future work.
The observations are intended to aid soft-robotics research, suggesting that robots could benefit from staged actions such as probing, anchoring and pulling rather than relying solely on material flexibility. Potential applications include search-and-rescue or underwater exploration devices capable of navigating confined spaces, although no functional robot based on these findings has yet been demonstrated.