Before I explain the basics of what thermoregulation is, I think it is first important to understand the difference between ectotherms and endotherms. When people say that reptiles are cold blooded animals it is a very confusing term to use. This is because the question that remains is, what temperature is deemed to be cold blooded and compared to what? Some times a reptile might have a blood or body temperature that is actually higher than our own.
What cold blooded really means is that reptiles cannot warm up their own bodies themselves from the inside like we can. Instead reptiles need to get warm from other things outside their bodies and this action is called thermoregulation. Thermoregulation is a crucial part of a reptile's life in order to maintain temperatures high enough for their body's metabolism to function properly. They seek out this heat in many ways for example it could be lying in the sun (basking), or finding a warm place to sit on like a rock. Reptiles and any animal that have to warm their bodies from the outside are called ectotherms. Any animal including our selves that can warm ourselves up from our inside are called endotherms (warm blooded).
Because a reptile does not have the luxury of having its body temperature automatically adjusted to suit its needs it is very important to provide areas with in its cage or enclosure, a wide range of temperatures choices. We call this different range of temperatures provided, a thermal gradient.
( see diagram 1 ).
It is important to remember that in the wild reptiles in most cases have many temperature zones in which to selectively choose according to their desire at the time. In captivity these gradients need to be recreated as best as possible.
Temperature directly affects the various biological functions of the reptile and a preferred optimum temperature will most likely vary between different species.
A reptile's metabolism is extremely poor at temperatures below 5 degrees celsius and much higher temperatures are required for tasks like digesting food etc. The reverse is also true, and temperatures can be too high for efficient metabolism as well. Although generally speaking the higher the temperature the more efficient a reptile metabolism, sustained temperatures above 41 degree celsius is often fatal to many reptiles.