How Does Skin Keep a Lizard From Getting Too Cold or Hot?

Reptiles are cold-blooded, or exothermic, which means they rely on sources in their environment to maintain a body temperature. They rely on outside temperatures to make sure they can digest food properly and keep from getting sick or dying. Depending on the species and where they live, there are different ways lizards use their skin to keep from getting too hot or too cold.

  1. Changing Skin Color

    • Some reptiles, such as the chameleon or the desert spiny lizard, will change their skin to a lighter color as the sun rises in the sky and the temperature gets hotter. Lighter colors reflect light and keep the sun's warmth from absorbing into the skin -- much the same way you would wear a white T-shirt on a hot sunny day instead of a black one. These reptiles will also darken their skin to absorb the light and warmth to get warm when temperatures drop.

    Skin and Body Expansion

    • The more mass a body has, the more it can absorb heat from external sources, such as heat lamps or the sun. Reptiles will flatten themselves out or puff out their rib cage as much as possible to expose as much of their skin as possible to the warming light. A bearded dragon will bask in the sun and expand the spiny skin around its neck to absorb heat while allowing for more air flow over the body to keep it from overheating.

    Conduction

    • Lizards will find a hard, warm surface on which to sit, such as a rock, to absorb heat from that surface. These hard, smooth surfaces conduct heat and will often hold onto it for a while after the sun has set. Reptiles bring their bodies closer to the surface by bending their legs, putting their heads down and lying flat against the surface. This is why some reptiles will spend so much time lying on a road -- they are trying to soak up the warmth left by the sun. The bearded dragon will also stand up on its hind legs in the heat of the day to distance itself from the hot ground so it doesn't overheat.

    Directions

    • To soak up as much warmth from a light source as possible, a lizard will lie perpendicular to the direction of the sun, so that the light is touching more of its body. Inversely, to cool down, the reptile will turn so it is lying parallel to the light. If the lizard's head or tail is facing the sun straight on, a smaller portion of its body is receiving the light.