Most reptiles rely solely on external sources of heat, whereas birds and mammals use internal heat from their bodies. Reptiles regulate their body temperatures by taking advantage of different sources of external warmth, such as direct sunlight, warm stones and logs, and the heat of the earth. By using such heat sources, reptiles are able to regulate their body temperature. This is called thermoregulation. They move into shade or a cooler area, which will cause their body temperature to drop.
Heat can be delivered as top heat or bottom heat, however, a combination of the two is best.
Top Heat Top heat warms the entire terrarium and provides heat for your pet to bask in. Incandescent flood lamps or bulbs can be screwed into a bulb clamp and attached to the side of the terrarium. The light should be positioned above a branch or other elevated feature in your terrarium. Your reptile will move up the branch to increase the heat it absorbs and move back down to reduce the heat. The residual heat will warm the rest of the terrarium to the desired coller range.