Faced with a predator, the common octopus combines several simultaneous tactics: it releases a cloud of ink to blur the attacker's sight and smell, propels its soft body at high speed with a jet of water, slips into the slightest crack thanks to the absence of a skeleton, and can sacrifice an arm to flee.
A leak on several levels
The ink, produced by the melanin pocket connected to the funnel, does not only serve as a visual screen: it contains compounds which disrupt the chemical and olfactory receptors of predators such as moray eels or certain fish, delaying their pursuit until the octopus disappears. This cloud, expelled in a fraction of a second, sometimes forms a pseudomorph, a mass which roughly imitates the silhouette of the animal and deflects the attack.
In the same movement, the octopus contracts its coat and ejects the water contained inside through its funnel, propelling its body against the direction of the expelled water. This jet propulsion, although costly in energy, allows brief but effective accelerations to quickly move away from an immediate threat.
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Its body, lacking an internal skeleton, is limited only by the size of its horny beak, the only rigid part of its anatomy. This allows it to slip into rock cracks or gaps much narrower than its apparent diameter, a refuge inaccessible to most of its marine predators.
Finally, if an arm is grabbed, the octopus can abandon it by autotomy. The severed arm continues to contract and move on its own for a while, distracting the predator's attention while the animal escapes. The arm then gradually grows back over several weeks to several months.
Complementary defenses, not exclusive
These mechanisms add to camouflage: even before actively fleeing, the octopus seeks to blend into its environment by modifying the texture of its skin using muscular papillae, which allows it to imitate the relief of a rock or algae and avoid being spotted in the first place.
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