Why chameleons change color and what it has to do with tiny mirrors

Time of India

2 days ago

Chameleons have captivated scientists and casual observers alike for centuries, thanks to their iconic ability to change colour. This striking phenomenon has given rise to countless myths and misunderstandings — from the belief that chameleons change colour to match any background, to the idea that these shifts are purely camouflage-based.
But modern science paints a far more intricate and fascinating picture.
Beneath their scaly skin lies a sophisticated system of nano-crystals, light-reflecting cells, and pigment-containing sacs — all working in harmony to display a dazzling array of colours. These changes aren't just for hiding. They're a complex language of emotion, communication, and survival.
How chameleons actually change colour
Historically, scientists believed that chameleons changed colour using pigment cells — similar to how octopuses and cuttlefish do.
While pigments do play a role, the primary mechanism is now understood to be structural colouration.
At the core of this mechanism are iridophores — specialized cells located beneath the outer transparent layer of the chameleon's skin. These cells contain nanocrystals made of guanine (a compound found in DNA), which can reflect and refract specific wavelengths of light.
How the colour shift happens
When a chameleon is calm, the nanocrystals are tightly packed, reflecting shorter wavelengths like blue and green.
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But when the animal becomes excited, threatened, or is trying to attract a mate, its body adjusts the spacing of the crystals, allowing the skin to reflect longer wavelengths such as yellow, orange, or red.
This is controlled by the chameleon's nervous system — not pigment release. The exact arrangement and size of these nanocrystals determines what colours are visible. This structural approach to colour is far more energy-efficient than pigment-based colour changes and allows for a broader colour spectrum.
Why do chameleons change colour
1. Communication
Perhaps the most important reason for colour change is intraspecies communication. Male chameleons, especially during the mating season, will brighten their colours to attract females or display aggression toward rivals. A dominant male might appear more vibrant, while a submissive one might take on darker tones.
2. Thermoregulation
Chameleons are ectothermic — they rely on external heat sources to regulate their body temperature. By changing to darker colours, they can absorb more heat from the sun when cold. Conversely, they lighten their skin to reflect sunlight and stay cool in hotter conditions.
3. Camouflage and defense
While camouflage isn't the primary reason for colour change, it is still useful in predator evasion. A relaxed chameleon typically blends into green foliage using a combination of yellow pigment and blue-light reflection, giving it a green appearance. Some species can even mimic browns and grays to blend into tree bark or dead leaves.
4. Mood and stress response
Changes in colour also correlate with a chameleon's emotional state. Stress, fear, or aggression can all trigger rapid colour changes. Even environmental factors such as lighting, humidity, and habitat structure can play a role.
What colours can chameleons display
The range of colours a chameleon can display varies by species. Some species, like the panther chameleon (Furcifer pardalis), can shift through a vivid palette — including red, orange, turquoise, and deep purple. Others, like the veiled chameleon (Chamaeleo calyptratus), have more limited transitions between greens, browns, and yellows.
In a 2015 study published in Nature Communications, scientists discovered that some chameleons even have two layers of iridophores — one for visible colour change and another for reflecting infrared light, which may offer protection from the sun or enhance thermoregulation.
The anatomy behind the transformation
Chameleon skin is made up of multiple layers:
Outer transparent layer
: The visible surface is actually clear, allowing light to reach the layers underneath.
Upper iridophore layer
: Responsible for rapid colour changes, containing guanine nanocrystals arranged in a lattice-like structure.
Lower iridophore layer
: Reflects infrared light and contributes to heat regulation.
Pigment cells (Chromatophores)
: Beneath the iridophores, these hold pigments such as red and yellow, adding depth to the final visible colour.
These layers work together like a complex optical instrument, turning the chameleon's skin into a canvas for emotional and environmental expression.
Chameleons' fast facts and fascinating discoveries
Chameleons can't change to any colour — each species has a genetic limit to the palette it can display.
The colour change is reversible — and can happen in just seconds.
Some scientists believe colour changes also play a role in UV signaling visible only to other reptiles.
Chameleons can shed their skin in patches — especially when switching to more dramatic tones quickly.
Do chameleons make good pets
Chameleons, especially species like the veiled chameleon or Jackson's chameleon, are popular among exotic pet enthusiasts. However, they are high-maintenance reptiles requiring:
Controlled humidity and temperature
Specialized UVB lighting
A vertical habitat for climbing
A diet of live insects
They also stress easily and should not be handled frequently, making them better suited for observation rather than interaction.
FAQs about chameleons
Why do chameleons change colour?
For communication, thermoregulation, camouflage, and emotional expression.
How do chameleons change colour?
By manipulating nanocrystals in iridophore cells beneath their skin to reflect specific wavelengths of light.
Can all chameleons change colour?
Yes, but the range and intensity of colours vary by species.
Do chameleons change colour to match their background?
Not exactly. While they can blend in, colour change is more often about mood and social signaling.
Are chameleons colour blind?
No. In fact, they have excellent vision and can perceive ultraviolet light, giving them unique insights into their surroundings.