Because reptiles are cold-blooded they cannot regulate their body temperature on their own. This is why you will often see reptiles laying on rocks and in direct sunlight because that is how they warm their blood and body. Since reptiles in captivity cannot move into the sunlight and shade to regulate their body temperature, they need reptile heating mats, heating pads or an under-tank heater in their captive environment to provide warmth.
It is important to remember that reptile heating mats and reptile heating pads cannot be placed under the entire tank or the reptile won't have anywhere to get away from the heat being provided by the under tank heater.
At IncubatorWarehouse.com we have our own line of reptile heating mats and reptile heating pads. Our Repti-Warm Reptile Heating Mats are very rugged and ultra-thin. These under-tank heaters can be ordered in almost any size, with 3 widths to choose from and a customizable length that can be used in almost any environment.