THERMOREGULATION
The maximum temperature at which a lizard can survive varies with the natural habitat of the species. Temperate lizards die when the temperature exceeds 30° C, tropical ones at above 35° C, and desert lizards cannot exist in temperatures above 46° C.
Tropical species can estivate at times of drought; temperate and subtropical species can hibernate.Heliothermic shuttling
Using the hypothalamus as a thermostat (and the parietal eye in some species), lizards alter their behavior to regulate their body temperature. In the early morning, lizards choose to bask on vegetation rather than on rocks that have cooled during the night and that would absorb heat from them. Later they move to the more solid surfaces, which have heated up by then. If they get too hot they seek shade and, as sunset approaches, they seek shelter before the cold night (Pough 1998c).
Color change
Many lizards are dark colored in the morning, which enables them to absorb heat and lighten in color as the body warms up. Some desert lizards have scales with different infrared absorption dorsally and ventrally so they can absorb or emit heat depending on the time of day (Bellairs 1969d).
Body posture
Desert lizards can stretch their limbs and lift their bodies high above the warm surface. Others use the heat of solid objects warmed by the sun; for example, geckos may rest under the bark of trees.