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How do lizards regulate their body temperature by moving between sun and shade?

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A painted turtle (Chrysemys picta) with a dark shell and red and yellow markings rests on a rock near water, surrounded by green aquatic plants. — reptile Painted turtle (*Chrysemys picta*).

It is a common misconception that the term "cold-blooded" implies a lizard's blood is always cold; in reality, this is a misnomer, as their blood can be as warm as or warmer than that of mammals when they are active.1

Lizards are ectothermic animals, meaning they rely on external heat sources rather than internal metabolic processes to regulate their body temperature. To maintain a "preferred temperature"—typically between 28 and 38 °C (82 to 100 °F)—lizards utilize behavioral thermoregulation.21

By moving between sun and shade, lizards control their heat absorption. A typical diurnal lizard will emerge in the morning to bask in the sun, often orienting its body to maximize exposure to solar radiation until it reaches its optimal temperature. If the lizard becomes too hot, it retreats to cooler, shaded areas to prevent overheating. This precise movement allows them to optimize physiological functions, such as hunting and escaping predators, though it involves trade-offs, as time spent thermoregulating cannot be used for feeding or reproduction.21