The Basking Spot: Thermometers and Thermostats – November 2012

The Reptile Times

The Basking Spot

By Jennifer Greene

Thermometers and Thermostats

One of the very first things we learn about reptiles and amphibians is that they are “cold blooded”, or ectothermic, and as such are deeply dependent on their environment for their temperature needs.  In captivity, we, the keepers are responsible for providing them with suitable caging that allows our pets to seek out the conditions they need.  While reptiles do need to maintain a body temperature within a specific range, they do best when offered a range of temperatures to select from and utilize to maintain their own preferred body temperature.  This means controlling the amount of heat added to the cage, as well as accurately measuring temperatures within the cage.

You can measure the temperatures in the cage using a thermometer, which comes in a variety of options. Stick-on thermometers are the most inexpensive, and are ideal for getting a general idea of the temperatures within the cage.  Stick on thermometers most accurately tell you the temperature of the surface they are stuck to, so keep in mind when using them that air temperatures can be much cooler or much warmer than what the stick on thermometer reads.  However, they can be useful when placed on the glass directly touching a heat pad (allows you to check that it is working properly), or just to see at a glance that the cage is an acceptable temperature.

stick on thermometer

The next step up that is commonly used is a dial thermometer, or analog thermometer.  Because these are attached to one section of the cage and usually immovable, they are most useful for determining ambient air temperatures rather than specifics about areas within the cage.  When it comes to monitoring ambient temps, analog thermometers are my preferred type, as you can see the ambient air temp at a glance.

Analog thermometer

For more precise temperature readings, a digital thermometer with a probe is ideal.  To leave in the cages at all times and see temperatures at a glance, digital thermometers are the best you can use.  There are several brands, with some having memory that enables you to see the highest temperatures recorded as well as the lowest.  These thermometers with memory are extremely useful for monitoring temperatures when you’re not around, as well as testing new cages you are setting up to ensure they are reaching the desired temperatures.  Using these thermometers is delightfully easy – simply place the probe in the location that you’d like to know the temperature of (so inside the warm side hide, on top of a basking spot, or along the cool side) and check the screen!

digital thermometer

When it comes to measuring surface temperatures instantly and easily, the use of a temp gun is ideal.  Many advanced keepers prefer to use a temp gun to measure their temperatures, as the instantaneous readout of the temperature of the surface in question is extremely useful and efficient when it comes to maintaining larger collections.  Temp guns only measure the surface temperature, however, and ideally should be used with a thermometer that will measure the air temperature as well.  Temp guns are quite accurate, though, and as I said, when it comes to maintaining larger collections they are indispensable.

temp gun

A fantastic tool for any herper is the thermostat.  Thermostats work by maintaining your heating element for you, turning your heat sources off and on as needed to maintain a specific temperature that you determine. Rheostats are similar, and work much like a dimmer.  When using a rheostat, you simply dial down the level on the light bulb or heat pad plugged into it until it reaches the level you desire.  The downside to a rheostat as compared to a thermostat is that it does not maintain a specific temperature – you have just dialed down the intensity of the heat.  If temperatures in your home drop or spike significantly, then the rheostat will not compensate for that.


Thermostats work in two ways – proportional or analog.  A proportional thermostat, such as those manufactured by Helix, increases or decreases the amount of heat being put out by the devices plugged in to it.  This gradual increase and decrease is much gentler and less abrupt on the animal, as well as extends the life of the bulb.  An analog thermostat will turn your heating elements off and on to maintain the temperature you set – once the temperature goes above the temperature you’ve set, it will turn the heat off, and once it drops below the set temperature, it will turn the heat on.  Which you use is entirely up to you.

The combination of an effective thermometer to check temperatures throughout the cage, as well as a thermostat on your heat bulb or heat pads, will help ensure that your cage is maintained at the correct temperatures.