The Sunning Chameleons- What are they really up to?

The myriad ways in which nature works never ceases to amaze me. I was reading the other day, a paper by Dr Kristopher Karsten and associates from Texas Christian University in Fort Worth, about the behaviour of lizards basking in the sun. The paper fascinated me with its depth of observations.

Till now it was assumed that the lizards bask in the sun to thermoregulate their body temperature. But latest research by Karsten and associates has added a new dimension to what seemingly is a lazy action by the lizards. Dr Karsten discovered that the main function of sun basking by lizards is to acquire vitamin D from sunlight.

To test the assumption that chameleons alter their sunning behavior based on dietary vitamin D intake, Dr Karsten observed the behavioral pattern of two different groups of chameleons. One was fed crickets dusted with a vitamin D powder. The other group was fed on regular crickets and thus had low vitamin D content. The chameleons were then placed in individual outdoor enclosures that offered open area for direct sun, and a tree to offer filtered sun. The animals were free to move between sunny, UV-rich areas and shaded low-UV areas. Chameleons fed on low vitamin D diet readily compensated lack of Vitamin D by increasing their exposure to the sun’s UV rays. According to Dr Kristen “The chameleons were as effective as mathematically possible by our methods at regulating toward optimal UV exposure for their vitamin D profile,”

Scientists have not been able to find out the exact mechanism that enables the lizards to sense their internal vitamin D levels. Dr Karsten thinks there may be a brain receptor sensitive to the vitamin d levels which triggers the behavior of sun basking. Getting to know the intricacies of why lizards do what they do will certainly help people who manages animals in captivity.

Details of the research appears in the May/June issue of journal Physiological and Biochemical Zoology