An octopus squeezing through a tiny hole can look as though it is pouring itself through the opening. Close-up recordings reveal something more organized: a sequence of probing, repositioning and bracing that helps the animal pull its body past the barrier.

The research team included Wenci Xin, Michael J. Kuba, Tamar Gutnick, Daniel Abed-Navandi and Cecilia Laschi. They studied common octopuses, Octopus vulgaris, and conducted additional exploratory experiments with Mayan octopuses, Octopus maya. Their analysis of octopus squeezing strategies turns an impressive escape behavior into a set of actions researchers can analyze.

“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,” Xin said. Understanding that coordination could complement existing octopus-inspired robotic arms, which already draw engineering lessons from the animals’ dexterity.

The main experiments involved three subadult common octopuses. Researchers placed clear acrylic partitions inside aquaria, leaving a central opening through which each animal could pass. Cameras recorded the movements from at least two viewpoints, allowing the team to track individual arms and the order of actions.

Rather than judging hole size against the animal’s soft outline, the researchers measured the distance between its eyes. They used this as an indicator of the cartilage capsule surrounding the central nervous system. That provided a reference for comparing the opening with a less deformable part of the body.

One octopus, with an eye spacing of 15 to 20 millimeters, encountered a 20-millimeter opening. The other two, with eye spacing of 30 to 35 millimeters, encountered 30-millimeter holes. Across 33 recorded trials, three unsuccessful trials involved escape attempts elsewhere that damaged the apparatus; 30 trials entered the main strategy analysis.

The simpler sequence began with exploration. An octopus inserted one arm through the opening, producing a bend near the hole and extending the arm beyond it. This probing movement established initial contact with the unfamiliar space before additional arms followed through the same narrow passage.

Next came the shifting stage. Several more arms threaded through, filling much of the available opening. The number shifted ranged from three to five in the reported analysis, with four most common. The remaining arms, head and bulbous mantle stayed on the starting side during this stage.

The final action depended on leverage. Two arms that had already crossed twisted backward and attached their suckers to the far side of the partition. By stiffening and extending against the surface, they generated force that pulled the remaining arms and body through together.

The sequence shows why flexibility alone does not explain the feat. The animals also need attachment and coordinated force. Those same challenges appear in soft-robot research at NUS and in an earlier eight-arm underwater robot designed to combine locomotion with grasping.

The common octopuses facing relatively smaller openings divided the final movement into two parts. After probing and shifting, they first transferred the remaining arms through the hole. Only afterward did they pull the head and mantle through, producing the four-step sequence described in the paper.

During the arm-transfer stage, the animals rotated their bodies upward. Twisting and extending movements helped bring the remaining arms past the partition. Once every arm had crossed, the animals restored their orientation and used arms braced against the barrier to pull the final body section through.

Side views also showed the mantle actively changing shape and reducing its diameter before passage. However, the recordings focused mainly on the arms and head. The researchers could not systematically analyze mantle movements, leaving an important part of the squeezing mechanics for future experiments.

The Mayan octopuses did not complete the same tight-hole maneuver. Four juveniles initially showed no attempt to squeeze through the smaller opening, preventing a comparable systematic analysis. Additional tests showed successful passage through larger openings using the three-step sequence observed in common octopuses.

When offered several openings, a Mayan octopus explored a smaller one and shifted two arms through, but did not complete the next stage. It eventually moved to the larger central opening and passed through. The observations do not establish that Mayan octopuses generally lack the four-step strategy.

The common-octopus sample also limits the conclusions. Each of the three animals was tested under only one relative hole-size condition. Consequently, the association between strategy and opening size could partly reflect individual differences. Repeated trials improve the behavioral record, but they do not replace testing more animals.

Arm use carried another caution. Front-left arms often initiated probing, but the setup provided clearer visibility on one side. That could explain the apparent bias. A different multi-arm foraging study found broadly shared arm use, illustrating why task conditions matter when interpreting octopus-inspired control principles.

For engineers, the lesson from octopus squeezing strategies concerns organization as much as softness. A robot might combine simpler actions such as probing, anchoring and pulling into a coordinated sequence. Dividing a difficult passage into stages could reduce the burden of controlling every part of a continuously deforming body at once, while preserving useful options for adjusting movement when contact changes.

Search-and-rescue and underwater exploration remain potential applications. A machine able to change its effective shape could negotiate passages that would block a rigid body. However, the study tested animals, not rescue robots, and did not demonstrate a working system navigating rubble or operating during a disaster.

The next biological tests need more individuals, several opening sizes for each animal and better measurements of mantle deformation. Even so, the recordings provide a useful starting point. An octopus does more than fit through a gap: it creates contact, finds leverage and moves different body parts through in an organized order.

These resources explore coordinated arm behavior, muscle anatomy and machines inspired by octopuses. Entries appear from newest to oldest and exclude the current study.