How octopuses squeeze through tiny holes—and why species differ
Testing tight-space skills
Marine biologist Wenci Xin of the National University of Singapore and colleagues studied Mayan octopuses (Octopus maya) and young common octopuses (Octopus vulgaris). Their research, published in the Journal of Experimental Biology, examined how the animals passed through small openings.
The researchers measured the distance between each animal’s eyes as an estimate of the width of its cartilage sheath. That distance ranged from about 0.6 to 1.3 inches. The team built clear plastic aquarium boxes connected by holes slightly wider or narrower than each octopus’s eye-to-eye measurement.
A route through wider openings
When faced with a comparatively large hole, the octopuses first explored it with their arms and sent one limb through. Usually, that was one of the two left front arms. They then passed as many as five more arms through the opening.
Two of those limbs reached back and attached to the first box’s walls with their suckers. The octopuses extended and stiffened the arms to push against the wall as they moved their other limbs, mantle and head through. The transition took about 20 seconds on average.
Different responses to narrow holes
Narrower openings restricted how many arms could pass through at once. Common octopuses handled the final movement in two stages: pulling their remaining arms through, then compressing the mantle and moving the rest of the body through.
Mayan octopuses did not test the narrow holes. They stayed in another corner of the box until a second, larger opening was available. Then they explored the smaller hole but chose the larger one.
What the findings suggest
The study covered only two species, but the results point to different ways of navigating tight spaces. They also suggest that cranial cartilage may set at least some limits on how much an octopus can compress itself.
Xin said there had been no information about how octopuses pass through openings far smaller than their body diameter. The researchers’ trials indicate that an octopus may try an opening if it appears able to fit.
Key points
- The researchers tested two octopus species in boxes linked by differently sized holes.
- Common octopuses used a two-stage maneuver to pass through narrower openings.
- Mayan octopuses avoided the narrow holes and chose larger ones when available.
- The findings suggest both species differences and cartilage-related physical limits.