Colour changes of chameleons are not only for camouflage
Chameleons are the extraordinary creatures on earth. It is well known that they change their colour to camouflage themselves. They put it to good use to avoid predators. For example, when a bird approaches from the sky, chameleons can darken their skin to resemble the ground colour. However, if they are attacked from the ground such as by a snake, chameleons can change to slightly lighter colour to match the sky. In addition to the camouflage, chameleons move very slowly which makes them extremely hard to find.
Colours reflect their emotions
Camouflage is not the only reason why they change their colour. In fact, their appearance also change depending on their mood, which means they communicate through their colour. This is significant especially for mating behaviour and fighting.
When the male chameleon find a female, he changes to very bright colour. Of course, the female chameleon will not respond to this all the time. Only when she’s ready she changes her colour in response. About a month after the mating, the female veiled chameleon will dig a hole and lay their eggs. The mother leaves her eggs in the ground, never see her babies again. After the babies hatch, they go out of the ground and start eating insects (see these amazing pictures and videos from here.)
The male chameleons also change their appearance when they encounter another male. In this video, two male chameleons were put in the same space. Both shifted their colour to bright green and their fight escalated to the physical attack. Interestingly, those with brighter-coloured head tend to win the physical fight. The colour pattern might be used to evaluate the quality of the competitor.
To find out more:
Using lights to change colour
The next question is, how do they create these colour combinations to send social cues?
In the chameleons’ skin, there are some cells containing yellow pigments, cells containing red pigments around the stripes, and cells with nano-crystals. Also, there are the cells with melanin which moves down when chameleon is excited, showing its bright colour.
Using these layers, chameleons are creating the colours by controlling the reflection of light by the tiny crystals in their skin cells. Chameleons tune the distance between the crystals when exposed to pressure or chemicals. The colour changes from red to orange to yellow to green to blue as the spacing decreases. So when chameleons are relaxed, the distance between crystals is smaller, reflecting blue and green. When they are excited, the distance increase, reflecting red, orange, and yellow. (For more information)
This mechanism of changing colour with light can be used to create camouflage clothing, chemical, coating and environmental sensors. Perhaps Harry Potter’s invisible cloak might be the real thing in the future. (New ‘smart’ skin changes color using a trick learned from chameleons)
The beautiful colour patterns of chameleons are not only to protect themselves from predators but also for reproduction purposes. To pass their genes onto the next generation, colouring is definitely one of the important factors for chameleons.
Interested in chameleons?
Explore your curiosity from here:
Long and muscular tongue. How are they catching prey? : Evidence for an elastic projection mechanism in the chameleon tongue
Eyes can move separately. Are they independent? : Eye movements in chameleons are not truly independent – evidence from simultaneous monocular tracking of two targets