FAQ: Heating & Lighting for reptiles

A faulty thermostat can leave a heater permanently on or completely off, which is why the terrarium temperature should be checked regularly with a thermometer. If you notice a fault, switch the heater off for now, watch the reptile and replace the thermostat as soon as possible.

Not entirely, because a thermostat only measures the temperature where its probe sits. A separate thermometer helps check that the thermostat is accurate and shows the temperature in other zones, such as the cool side.

At least two thermometers are usually recommended, one on the warm side and one on the cool side of the terrarium. That way you see the whole temperature gradient and can be sure the reptile has somewhere to warm up and somewhere to cool down.

Stick-on thermometers show the temperature of the glass rather than the air or a surface, and they are often inaccurate. A digital thermometer with a wired probe measures precisely where the reptile is and often records the day’s maximum and minimum.

An infrared thermometer shows a surface temperature in seconds, for example of a basking rock or branch. This matters because a reptile warms itself lying on a surface, and air and surface temperatures can differ a lot.

A hygrometer measures air humidity, which matters to reptiles as much as temperature: air that is too dry makes shedding hard, and air that is too damp encourages mould and breathing problems. Heating changes humidity, so a device that shows both readings is handy.

Put the thermometer probe at the reptile’s level rather than near the ceiling, because the temperature high up and near the floor can differ a lot. Measure in the warm zone near the basking spot and in the cool zone by a hide.

The simplest way is to compare several thermometers in the same spot or check them against an infrared thermometer. If the readings differ by several degrees, replace the unreliable device, since your heating settings depend on it.

A gradient is the temperature difference between the warm and cool parts of the terrarium. It is needed because a reptile regulates its body temperature by moving between zones, so heaters go at one end while the other is left cooler.

If the whole terrarium is heated, the reptile cannot cool down and may overheat. Heating one end creates warm and cool zones, and the animal itself chooses the temperature that suits it at the time.

For many reptiles a night-time drop in temperature is natural and even beneficial, so if the room is warm, no extra heating is needed at night. If the temperature falls below the species’ safe range, a heater that gives no light is used with a thermostat.

For many species the temperature can drop by a few degrees at night, and for desert species somewhat more, but the exact limits depend on the species. Check your reptile’s needs and track the night temperature with a thermometer that records the minimum.

Bearded dragons are usually recommended a hot basking spot of roughly 38–42 °C on the surface for adults and a cool side of about 24–28 °C. For juveniles the basking spot is usually a little cooler; fine-tune the temperatures by the animal’s behaviour and a vet’s advice.

Leopard geckos are usually recommended a warm zone of about 30–33 °C on the surface and a cool side of about 22–26 °C. Since they also warm their bellies, the warm spot is often created with a mat or a lamp over a flat stone, run on a thermostat.

Crested geckos like moderate room temperatures and tolerate heat poorly, so in a warm flat they often need no extra heating. If the room is cool, a low-wattage basking lamp is used at the top, and the terrarium must not overheat in summer.

Ball pythons need a warm zone, a cooler side and fairly high humidity. A ceramic or infrared heater or a mat on a thermostat is often used for heating, and it is worth checking the temperature inside the hides on both sides.

Corn snakes usually need moderate heating, with a warm zone at one end and room temperature at the other. A basking lamp, ceramic heater or mat on a thermostat all work; the key is to protect the snake from direct contact with a hot surface.

Chameleons need a strong UVB lamp and a low-wattage basking lamp at the top of the terrarium, with cooler conditions lower down. They overheat easily, so the basking temperature must be measured carefully and the lamp shielded with a guard.

Green iguanas need a large, warm enclosure with a wide basking zone, a strong UVB lamp and enough humidity. Because adult iguanas are very large, several lamps are often needed so the heat covers the whole body.

Indoors a tortoise needs a basking lamp at one end of the enclosure, a UVB lamp and a cooler zone with a hide. Because a tortoise is large and warms slowly, the basking zone must be wide enough to heat the whole shell.