🐙 How Octopuses Think, Hide, and Hunt

The Perpetually Curious!

🐙 How Octopuses Think, Hide, and Hunt

Originally published: November 2026

Canonical source: https://www.theperpetuallycurious.org/articles/octopus-intelligence/

At the mouth of a rocky crevice, an octopus can explore a place its eyes cannot see. One arm slips inside while the rest of the animal stays outside. The suckers grip the rock and detect chemicals on the surfaces they touch. Its first hints of what lies inside can come from the far end of an arm.

That small reach offers a way into octopus intelligence. What the animal senses through its body can shape what it does next. An arm can feel for a meal or carry an object that becomes shelter. The same soft body can change its appearance or slip away behind a cloud of ink.

In the dim spaces between rock and water, an arm reaches where eyes cannot follow.
Beneath shifting colors, drifting ink, and silent currents, a life unfolds through touch, patience, and possibility.
The sea rarely announces its mysteries. It simply waits for them to be noticed.

🧠 How an octopus senses with its arms

An octopus has one central brain and extensive networks of nerve cells in its eight arms. Those networks handle some sensing and movement locally, a useful arrangement when an arm can bend and twist along its length. The suckers help the animal grip a surface, and specialized receptors let them detect chemicals on contact. Researchers often describe this as tasting by touch.^[1]

In one laboratory study, common octopuses (Octopus vulgaris) learned to reach through a maze with a single arm toward a visually marked compartment. A cue picked up by the eyes helped guide a limb that also gathers information of its own.^[2] On the seabed, an object that an arm explores and grasps can become a shelter.

🐚 When a shell becomes shelter

In Indonesian waters, researchers watched veined octopuses (Amphioctopus marginatus) carry discarded coconut shell halves across the seabed. An octopus could collect two halves and later draw them together around its body. Carrying them made movement awkward, and their value as shelter came when the animal stopped and put them together.^[3]

The researchers described carrying the shells for later use as defensive tool use. What the octopus anticipates during the journey remains an open question. A coconut shell gives it something to hide inside. For many octopuses, the skin itself offers another way to stay out of sight.

🎨 How skin changes color and texture

Tiny muscles stretch open pigment sacs in the skin called chromatophores. As the sacs expand, more pigment becomes visible. As the muscles relax, the spots shrink. Other structures reflect light and can give the skin an iridescent sheen. Some octopuses also raise small bumps called papillae, breaking up a smooth outline against rock or rubble.

The same skin can help an octopus stand out. Researchers watching gloomy octopuses (Octopus tetricus) recorded dark body patterns and raised postures during encounters between individuals.^[4] A change in skin pattern can make an octopus harder to pick out against the seafloor. A second kind of cover can form in the water around it.

☁️ What octopus ink does

Many octopuses release dark ink through the funnel, the same opening they use to jet water for movement. Melanin gives the ink its dark color, and mucus helps shape the discharge. A diffuse cloud can obscure the octopus as it moves away. In some ink-releasing cephalopods, the discharge can hold together in a shape that resembles the animal and may briefly draw a predator’s attention.^[5]

The roles change when the octopus is the one looking for a meal.

🦀 How octopuses use venom

In one field study, young octopuses used touch and chemical cues to search for prey in crevices and under rocks.^[6] A hard beak sits where the arms meet, and venom from the salivary glands can help an octopus immobilize its prey.^[7]

Blue-ringed octopuses (Hapalochlaena) carry tetrodotoxin in their venom. The toxin can cause paralysis, and a bite can be life-threatening to a human. Bright blue markings can appear when the animal is disturbed.^[8]

Tetrodotoxin also occurs in pufferfish and other animals. The blue-ringed octopus is one example of how animals use the same toxin in different ways.

🌊 How species meet different surroundings

Across habitats, the same eight-armed body plan offers different ways to find cover and move through water. In the coastal North Pacific, a giant Pacific octopus (Enteroctopus dofleini) can blend into the rocks around its den. On sandy bottoms in Indonesian waters, a mimic octopus (Thaumoctopus mimicus) can draw its arms together and swim with a silhouette like a flatfish. In the deep sea, dumbo octopuses (Grimpoteuthis) can move with paired fins that look like small ears.

A brooding female can spend much of her time tending a single clutch.^[9] At the opening of a crevice, an arm reaches into the dark. On a deep rock face, a female stays with her eggs. So much of life in a soft body depends on when to reach, when to slip away, and when to stay.

Pass this article along to someone curious and let the learning travel.

↗️ Let the wonder travel

Share this with someone who would linger with you over a small patch of sea, watching to see what moves.

📚 Educational context

This article introduces octopus behavior and physiology. The studies described involve particular species and settings, from laboratory observations to fieldwork on the seabed.