Here is a link to a very interesting study about bearded dragons and the relationship between coloration and the circadian rhythm (the daily activity cycle of systems in the body).
As I’ve grown older, I am more and more interested in the circadian rhythm in humans because living in harmony with it can really empower an individual and help to maintain a healthy body and mind. So this was an interesting study for me as I don’t see this often addressed with lizards, outside of recommending day lengths that perhaps change with the season to promote breeding behavior.
I feel that this study is particularly well done because it takes into account not only changes in coloration, but changes in reflectance of the skin for multiple spectrums of light at different times of the day, giving us a probable explanation of why coloration changes occur in bearded dragons throughout the daily cycle.
In the study, the circadian rhythm was also changed by changing the day/night lengths. Bearded dragons adapted quickly to these changes by adjusting their pigment cycle. Dragons then placed in the dark “remembered” the latest cycle they had been exposed to, and pigments continued to move through that particular cycle.
Really interesting stuff. Here’s the link: