Unlike humans, cold-blooded lizards use the environment to regulate their body temperature. Lizards bask in the warm sun and move to cool shade and burrows to maintain body temperature. Since lizards are only active when their body is at its ideal, warm temperature, the sunny, warm climate in the desert provides an environment where they can thrive.
Each species of lizard has a range of optimal body temperatures. For example, the desert iguana's body temperature range is 100 to 108 degrees Fahrenheit. In the active range of temperatures, lizards can hunt, eat, move quickly and reproduce. If the lizard's temperature drops below the ideal range, he will not be able to move quickly and metabolic processes will slow dramatically.
Thermoregulation is the process cold-blooded lizards use to maintain their body temperature. Lizards warm themselves using insolation and conduction. Insolation is the absorption of the sun's rays and conduction is absorbing heat from the ground. If the lizard gets too hot, he will move into the shade or a burrow to cool off. Some lizards have adapted to be able to change color. If a lizard turns a darker color, he will be able to absorb heat better than when he is a lighter shade.
During times of extreme heat, lizards will enter estivation, or a period of inactivity. Lizards also hibernate during the desert winters, when the temperatures do not rise enough for them to maintain temperatures high enough for activity. During these times, lizards typically live in burrows, surviving off the water and nutrients already in their systems. Gila monsters and geckos, for example, store water and nutrients in their fatty tails for these times of dormancy.
Although lizards must maintain adequate body temperature to remain active, being cold-blooded offers many advantages in the desert. While warm-blooded animals struggle to keep cool, lizards are able to enter estivation to keep cool. In addition, cold-blooded animals require far less energy to function than warm-blooded animals, who need a constant supply of food and water.
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