Octopuses squeeze through tight holes using a fixed sequence of arm movements

Octopuses follow a consistent, stepwise routine when escaping through small openings, according to a study in the Journal of Experimental Biology. Michael Kuba of the University of Naples Federico II and colleagues found that common octopuses (Octopus vulgaris) adjusted that routine according to whether a hole was wider or narrower than their most rigid body structure. Mayan octopuses (Octopus maya) behaved differently, mostly declining to try the narrower hole at all.

Measuring the limit of a soft body

Octopuses are largely muscle, which lets them change shape dramatically, but they do have some rigid parts. The team used the distance between each animal's eyes as a proxy for the size of the hardest cartilage surrounding the brain. They then built acrylic boxes with holes slightly larger or slightly smaller than that measurement for each individual and placed the animals inside.

The sample was small: three common octopuses and four Mayan octopuses. The findings are therefore best read as a systematic first description of the behaviour rather than a population-level estimate.

Three steps, or four

When the hole was wider than the eye-to-eye distance, common octopuses escaped in three stages. They first pushed one or two arms through, then threaded a couple more, and finally used the arms already outside to push against the box and pull the head and remaining arms through in a single movement. The whole sequence took a few seconds.

When the hole was narrower than that distance, the animals added a fourth step. All arms went through first, and only then did the head and mantle follow, squeezed through the opening.

A more cautious species

Mayan octopuses were less willing to try. Faced with the narrower hole, they generally ignored it. Kuba suggests the difference could reflect underlying biology or adaptation to habitat. Mayan octopuses live in sandy, rocky areas where they may shelter under rocks but seldom need to force themselves through tight gaps. The study does not test these explanations, so they remain hypotheses.

Why it matters

Robyn Crook, an evolutionary biologist at San Francisco State University who was not involved in the work, notes that although squeezing through gaps is among the best-known octopus behaviours, the strategies involved had not been examined systematically. The skill has ecological importance too: octopuses use it to reach hidden food and to avoid predators.

The work also interests roboticists. Wenci Xin of the National University of Singapore says such abilities could let soft robots enter spaces that are otherwise hard to reach. Robots designed for tight spaces are currently often snake-shaped, and an octopus-inspired sequence of arms leading and body following would represent a different configuration.

Open questions

Only circular holes were tested. Crook points out that octopuses may use other tactics for slit-like or tube-like openings, which are common in natural settings and on boats and in aquaria. Larger samples, more species and a wider range of opening shapes would show how general the sequence is, and whether the contrast between the two species reflects evolutionary history or ecology. Comparing arm coordination and neural control across those conditions would also help to explain how a largely soft animal plans such movements, a question relevant to both comparative neuroscience and soft robotics.

Source: How octopuses squeeze through tiny openings, step by step (Science News, 6 November 2026).

Image: AI-generated illustration.