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Why do Octopuses Change Shape and Color?

Cephalopods, including octopuses, cuttlefish, and squids, possess a remarkable ability to change the color, pattern, and texture of their skin at a pace unmatched in the animal kingdom. Michael Vecchione, curator of Cephalopoda at the Smithsonian National Museum of Natural History, highlighted this phenomenon, noting the evolutionary significance of these adaptations, especially given that most cephalopods are color-blind.

Cephalopod skin is covered in millions of chromatophores—pigment-filled cells controlled by tiny muscles—that enable the creatures to produce a wide array of patterns. Additionally, features like papillae allow octopuses and cuttlefish to alter their skin’s texture. These abilities enable cephalopods to blend into various environments seamlessly. For instance, the common day octopus can transition from sandy beige to rugged, dark tones on rocks, while baby giant cuttlefish mimic swaying seaweed.

Beyond camouflage, cephalopods use their dynamic skin changes for defense and communication. When threatened, many octopuses darken and elongate their bodies to appear larger and more intimidating. Cuttlefish can create eye-like patterns to deter predators, while the venomous blue-ringed octopus flashes bright rings as a warning. The mimic octopus takes deception further, imitating dangerous animals like lionfish to avoid threats.

Cephalopods also employ their color-changing skills in predation. The broadclub cuttlefish, for instance, sends ripples of a dark color to mesmerize prey, while the tropical octopus uses patterns to create illusions, tricking prey into revealing themselves. Social species like the Humboldt squid use bioluminescent cells called photophores for communication in the dark depths of the ocean.

In mating displays, male cephalopods use vivid color changes to attract females or deter rivals. For example, male Caribbean reef squids turn dark red, and male Australian giant cuttlefish disguise themselves as females to sneak past larger males.

While cephalopods’ skin changes are often viewed as intentional acts of mimicry or communication, scientists suggest these behaviors may be involuntary responses to brain activity. This idea is supported by observations of octopuses changing colors while sleeping, possibly indicating dreams.