How Does A Chameleon Change Its Colours?

A Chameleon reflects light off the nanoparticles that are embedded beneath the skin to change its colours. But it doesn't do so to match its environment.

Everybody who has seen a recent three-minute video apparently captured in Madagascar of a chameleon changing its colour seven times - from red to orange to green to yellow to blue and ending at brown, have been caught up in its awe. Hardly an easy sighting in the wild, if at all, at best one can witness a chameleon adapt to the green of the surrounding leaves or the brown bark of the trees.

How many colours can they change?

Different chameleon species vary their colouration and pattern in idiosyncratic ways. The foundation colour is green and sometimes marked with brown, white, beige, black, yellow and orange streaks and blotches. The other colours eventually emerge as the creature grows up. While toggling between brown and green is standard, there are some species which can change to almost any hue. It could be red, orange, pink, light blue, turquoise, purple, yellow, tan and can even be black blotches and stripes.

They might take as little as 20 seconds to change between colours.

How does a Chameleon change its colours? 

Unlike some animals like cuttlefish, squid and octopus which change their colours primarily by distributing their pigments called chromatophores embedded beneath their skin, these lizards rely on structural changes. They have two superficial layers of cells, termed iridophores, which contain guanine crystals - a nanoparticle which determines how light reflects off the skin.

A relaxed chameleon will have its iridophores tightly packed, reflecting blue and green tones which are of shorter wavelengths. But under threat, the cells get stretched out, resulting in generating reds and yellows, which evidently are considered as warning signs in the natural world.

Doesn't Chameleons Change Colour To Blend With Surroundings?

That's actually a myth. Chameleons do not change colour to match their environment; rather, it is dependent on mood, temperature and or stress. When happy they will be mostly green and light blue, but bring them closer to a vet (many have them as pets), they will change to a darker colour or even black, sometimes curling themselves to a fetal position. If angry, they tend to exhibit dark red with black stripes/linings.

That in a natural habitat, it works out favourably for them, can only be attributed to natural selection. Don't you think a turquoise or a violet chameleon could be easy meat to its predator.

Only while shedding, the skin bears white flakes all over. Interestingly, just before it dies it curls up, turns bright green and after death, it turns into a darker shade presumably to absorb heat from its surroundings.