Biology
Animal Colour Change
Quick fact
The cuttlefish can change both its colour and skin texture in under a second, making it one of the fastest colour-changing animals on Earth.
Why this is interesting
Most people think only chameleons change colour, but many animals—including cuttlefish, frogs, and even some fish—can transform their appearance in seconds. What enables this remarkable ability, and why do they do it?
Read the full explanation
Understanding Animal Colour Change
Animals change colour for several reasons: to hide from predators, to signal to mates or rivals, to regulate body temperature, or to blend into different backgrounds. The key players are pigment-containing cells called chromatophores, which lie in the skin. When these cells expand or contract, the colour of the animal shifts. For example, a chameleon can turn green by spreading yellow pigment cells and allowing blue light to reflect from deeper layers. Colour change can be quick (a few seconds) or slow (over days), depending on the mechanism.
A deeper explanation
Colour change operates through two main mechanisms: physiological and morphological. Physiological change is rapid and reversible, controlled by the nervous system or hormones. In cephalopods like octopus and squid, each chromatophore is surrounded by tiny muscles that contract or relax, stretching or shrinking the pigment sac. This allows pattern changes in milliseconds. In chameleons, colour change involves nanocrystals in specialized skin cells (iridophores) that can be rearranged to reflect different wavelengths of light. Morphological change is slower and involves the synthesis or breakdown of pigment over days or weeks, often in response to seasonal changes or long-term background matching. Understanding these mechanisms reveals how evolution fine-tunes an animal's ability to survive in a dynamic world.