How do reptiles keep warm?

After the cool of the night reptiles have to warm up in the morning sun. This they do by basking until their body temperature is high enough to start their daily activities. Some reptiles flatten out to expose a greater body area to heat and so warm up quickly.

In colder climates many reptiles have dark bodies allowing them to absorb greater heat than will a paler body. You may have seen lizards lying on bitumen roads, particularly in rural areas. The black surface absorbs the heat from the sun and lizards often flatten out on the road to absorb this heat a bit like an electric blanket.

During the day reptiles shuttle between sun and shade in order to keep their temperature at the desired level. If it gets too hot, they will disappear into shelter. Nocturnal reptiles can operate at lower temperatures. Some of these will actually heat up under cover bu selecting sheltered spots that gets the afternoon sun.

Reptiles cannot just keep heating up all day. There is a critical point at which the temperature becomes lethal That point does vary between species but it can exceed 40 degrees C. If the reptile cannot reduce its body temperature, it will very quickly die. They must keep warm enough to be able to carry out their daily activities, but must also be wary of overheating.