Chameleons or chamaeleons (family Chamaeleonidae) are a distinctive and highly specialized clade of Old World lizards with 202 species described as of June 2015.[1] These species come in a range of colors, and many species have the ability to change color.
Chameleons are distinguished by their zygodactylous feet; their very extensive, highly modified, rapidly extrudable tongues; their swaying gait;[2] and crests or horns on their brow and snout. Most species, the larger ones in particular, also have a prehensile tail. Chameleons' eyes are independently mobile, but in aiming at a prey item, they focus forward in coordination, affording the animal stereoscopic vision.
Chameleons are adapted for climbing and visual hunting. They live in warm habitats that range from rain forest to desert conditions, with various species occurring in Africa, Madagascar, southern Europe, and across southern Asia as far as Sri Lanka. They also have been introduced to Hawaii, California, and Florida, and often are kept as household pets.
Change of color
Some chameleon species are able to change their skin colouration. Different chameleon species are able to vary their colouration and pattern through combinations of pink, blue, red, orange, green, black, brown, light blue, yellow, turquoise, and purple.[16] Chameleon skin has a superficial layer which contains pigments, and under the layer are cells with guanine crystals. Chameleons change colour by changing the space between the guanine crystals, which changes the wavelength of light reflected off the crystals which changes the colour of the skin
Colour change in chameleons has functions in camouflage, but most commonly in social signaling and in reactions to temperature and other conditions. The relative importance of these functions varies with the circumstances, as well as the species. Colour change signals a chameleon's physiological condition and intentions to other chameleons.[17][18] Because chameleons are ectothermic, another reason why they change color is to regulate their body temperatures, either to a darker color to absorb light and heat to raise their temperature, or to a lighter color to reflect light and heat, thereby either stabilizing or lowering their body temperature.[19] Chameleons tend to show brighter colours when displaying aggression to other chameleons,[20] and darker colours when they submit or "give up".[21] Some species, particularly those of Madagascar and some African genera in rainforest habitats, have blue fluorescence in their skull tubercles, deriving from bones and possibly serving a signaling role.[22]
Some species, such as Smith's dwarf chameleon, adjust their colours for camouflage in accordance with the vision of the specific predator species (bird or snake) by which they are being threatened.[23]
The desert-dwelling Namaqua chameleon also uses colour change as an aid to thermoregulation, becoming black in the cooler morning to absorb heat more efficiently, then a lighter grey colour to reflect light during the heat of the day. It may show both colors at the same time, neatly separated left from right by the spin.
