Rethinking Reptile Lighting - Part 1
In the early 1940s, our knowledge of the effects of light on reptiles and amphibians was very limited. It wasn’t until 1944 that we learned of the amazing ability of reptiles to maintain relatively stable body temperatures through thermoregulation. This was the result of a groundbreaking study by herpetologists Raymond Cowles and Charles Bogert, who coined the terms “ectotherm” and “endotherm.” Their landmark study inspired numerous research projects on the effects of light and heat on reptiles. Since then, our knowledge of reptile lighting has increased tremendously. We now know that many reptiles and amphibians can see things illuminated by ultraviolet-A, and that they can make vitamin D in their skin upon exposure to ultraviolet-B.
When housed in captivity without access to UVB, many reptiles developed a form of metabolic bone disease (MBD) that results in soft, deformed bones and is often fatal if not corrected by UVB exposure. With this knowledge came the introduction of the first commercially available UVB lamp for reptiles in 1993, which allowed people to successfully maintain and breed a variety of reptile species in captivity. Although preventing the onset of disease is good motivation to provide adequate lighting for captive reptiles, many keepers are going to the next level in an effort to accurately recreate truly naturalistic habitats, even with respect to lighting.
Humans see the world differently than reptiles and amphibians. Many reptiles and amphibians have the remarkable ability to see things illuminated by UV wavelengths. Also, some lizards and amphibians have a third eye on the top of their head known as the parietal eye. This eye cannot see the full complement of colors that the other two eyes see, but it can sense light and is associated with photoperiod regulation (circadian rhythms), reproductive behavior, basking behavior and thermoregulation. The parietal eye may also be sensitive to UV wavelengths (Jenison, 1980). These differences in how reptiles and humans see have caused persistent confusion on what defines full-spectrum lighting and UV lighting.
