The ability to change skin color is a relatively common phenomenon in lizards whose occurrence is often related to crypsis. Field observations suggest that Mediterranean geckos (an often ubiquitous introduced species in many metropolitan areas of the southern United States) have the ability to lighten and darken in response to their background. On light backgrounds, the geckos were typically light pink whereas on dark backgrounds they were typically much darker with a brownish hue to their skin. This study investigated the ability to background match in this species, the main effects of temperature (20, 25, and 30[degrees]C), illumination (total darkness and dim lighting), and their interactions on the lizard's ability to match their skin darkness to four levels of background darkness (black, gray, white, and a combination of the three). Each lizard was measured in a repeated-measures design. While temperature had little effect, illumination strongly influenced the lizard's ability to background contrast match. In the absence of light, 73% of the lizards were light in color. This suggests that lighter skin pigmentation in the dark may be the "default" setting with the melanocytes contracted. In dim lighting, the lizard's skin darkness closely matched background darkness in most cases (81%). These nocturnal lizards are typically associated with human development where low levels of illumination are often present at night. The ability of Mediterranean geckos to accurately background match under conditions of human habitation may have contributed to their success as a colonizing species.
Frederic Zaidan and P Weibusch. Effects of temperature and light on background color matching in Mediterranean geckos (Hemidactylus turcicus). Texas Journal of Science. 59, no. 2 (2007): 127-136.
The Texas Journal of Science