Britannica Sources used in this answer

Why does squid ink sometimes form a decoy shaped like the squid?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A blue-ringed octopus with bright blue rings on its beige body crawls over a rocky, coral-strewn seabed. — cephalopod Blue-ringed octopus (genus *Hapalochlaena*).

Squid ink is ejected as a spindle-shaped mass that coagulates in the water, effectively creating a "dummy" or decoy that mimics the size and shape of the squid itself. This decoy serves as a vital defense mechanism during an escape.12

By leaving this decoy behind, the squid is able to contract its chromatophores—the pigment cells in its skin—to become nearly transparent, allowing it to jet away while the predator is distracted by the ink mass. This behavior is distinct from that of octopuses, which typically use their ink to create a cloud that conceals their movement and may temporarily paralyze a predator's senses of sight and smell.13