Researchers detail coordinated steps octopuses use to navigate tight gaps
A team of biologists filmed common and juvenile Mayan octopuses, identifying a systematic sequence of arm and mantle movements that enable the animals to pass through openings of varying sizes.
Scientists from the University of Naples Federico II, the National University of Singapore and Vienna’s Haus des Meeres aquarium have captured octopuses navigating clear acrylic partitions, revealing a repeatable, multi-step process for squeezing through narrow gaps. In experiments with three common octopuses and four juvenile Mayan octopuses, the researchers recorded 30 successful passages and analyzed the footage frame by frame.
When the opening was relatively large, the animals completed the maneuver in three stages: an initial arm probed the gap, a second arm (left side in 47 % of trials) followed, and then three to five additional arms were threaded through. The inserted arms curled back, their suckers gripping the far side, allowing the octopus to stiffen, extend and pull the remaining limbs and body forward. For tighter openings, a fourth step was added; the octopus rotated upward, moved the remaining arms through first, and then pulled its head and mantle across, visibly narrowing the mantle to fit.
"So, we know that octopuses have to squeeze to either hide in crevices and caves to avoid predators," said Michael Kuba, a biologist at the University of Naples Federico II.
"On the other hand, they need to explore the same structure to look for food—octopuses often eat rather small prey, which is often hiding in crevices and caves in the rocky shores the common octopus likes to inhabit," he added.
"The organization and coordination of the arm activity is impressive, but I was most impressed by how they move their body/mantle through the hole," Kuba noted, describing how the mantle muscles contract and release during passage.
The study also confirmed that the traditional rule of thumb—an octopus can fit through any hole larger than its beak—is oversimplified. Successful passage required the arm bases and the cartilage surrounding the central nervous system to fit, with the distance between the eyes serving as a size proxy. Mayan octopuses avoided the smallest 10-millimetre openings, probing them before selecting larger gaps.
The researchers acknowledge limitations, noting that only three common octopuses were tested and each experienced a single hole size relative to its body. They plan further experiments to determine whether octopuses can assess an opening’s feasibility before attempting passage.
The findings may inform the design of soft-body rescue robots capable of navigating confined spaces, as engineers seek to emulate the octopus’s ability to coordinate numerous flexible limbs while processing extensive sensory input.