.png)
Think about what it feels like to sit in your favourite chair in a cozy, warm room inside your house. Now think about what it feels like to sit outside in the sun on a warm summer day. Do these two heat sources feel the same? Warmth from the sun tends to make us feel warm throughout our whole body, whereas warmth from a furnace or other artificial heat source feels external. Infrared radiation is what makes the sun’s heat feel so different to man-made heat sources. The sun’s rays contain ultraviolet (UV), infrared-A (IRA), infrared-B (IRB), and infrared-C (IRC) wavelengths. All of these wavelengths play an important role in maintaining life on Earth, particularly for reptiles. Captive reptiles do not have access to natural sunlight, therefore making it the keeper’s responsibility to mimic sunlight to the best of their ability to ensure their animal is able to carry out its natural functions and survive.
To recreate the same warmth provided by the sunlight, appropriate lighting and heat sources must be selected. There are a variety of heat sources available for reptiles, but not all of them create the correct infrared radiation (or any at all!). IRA, sometimes called near-infrared radiation, is the strongest of the infrared wavelengths. IRA significantly warms the surface of the skin, while also warming deep tissue and the muscles to allow the whole body to warm up. IRB, or mid-infrared, is almost as effective as IRA at warming the skin, but only 10% - 20% of it is absorbed by the muscles and tissue. Although both of these wavelengths are useful, when thinking of a cold-blooded animal that is ectothermic, IRA becomes significantly important.
Reptiles rely on warmth to not only help with digestion and to maintain a comfortable body temperature, but also to maintain proper functioning of their organs and vital systems. Even though IRB allows a small amount of heat to reach the muscles, a heat source that emits IRA should be incorporated into an enclosure to allow the animal to reach optimal temperature more easily. While a reptile can still reach their ideal body temperature with IRB waves, it will take a longer amount of time as the skin slowly conducts heat to deeper tissues.
The last wavelength, IRC, or far-infrared, is more of an ambient heat that warms up objects in the environment. It cannot effectively warm the skin, but it can allow surfaces such as slate rock to absorb heat throughout the day. Objects in the environment heat up from IRC, and store some of the heat to be released once the temperature of the environment cools down (or once the reptile’s lights are shut off). The amount of heat absorbed depends on the properties of the object and its location in the enclosure. For example, rocks placed closely together and stacked near the basking spot are likely to retain heat for longer as it will take them a longer time to cool down to the ambient night temperature than a piece of cork bark placed on the cool side of the enclosure.
To summarize, IRA can be considered as the most vital of the infrared wavelengths that helps the animal to function, IRB allows the skin to be warmed and helps with some functioning, and IRC helps the ambient temperatures of the enclosure stay warm. Despite the differences between these wavelengths, the ideal enclosure set up should include all three and a source of ultraviolet light to replicate sunlight.
Basking Bulbs (e.g., incandescent, halogen)
Basking lights, which are typically an incandescent or halogen bulb, are currently the best available source of IRA for captive reptiles. The most effective basking bulbs are ones around the 3000k colour range, meaning they emit a yellow-y glow when they are on. This colour is a result of the heat generated by the bulb, and not the colour of the glass. Colour tinted bulbs should be avoided as they do not necessarily create IRA and could be stressful for the reptile.
Halogen basking lights have the greatest heat and IRA output compared to other basking bulbs marketed for reptiles, and create more of a “flood” of light as opposed to lighting up one small area. A halogen flood bulb is more effective than a basking bulb marketed as having an intense beam as it will allow more of the reptile’s body to be exposed to the warmth and IRA, allowing them to reach optimal temperatures faster. Reptiles who are under a focused basking beam will bask for longer periods of time as they wait for the rest of their body to warm up, and there is the potential for minor burns if they get too close to the intense beam.
Infrared basking bulbs, or the all red basking bulbs, are not suitable to use. While they do create a significant amount of the heat, the red coloured bulb can be a source of stress for many reptiles. Contrary to popular belief, using a red coloured heat bulb at night does still disturb a reptile’s circadian rhythm as they are able to see the light being released from it. During the day, the red colour will mean the reptile’s world is tinted an odd colour and they will not get to see in their natural spectrum.
Ceramic Heat Emitters (CHE)
Ceramic heat emitters are a lightless overhead heat source that is commonly recommended as a way to boost ambient temperatures in a terrarium or to provide night time heat without disturbing the circadian rhythm of the reptile. Although CHEs can help raise ambient temperatures, they do not emit IRA or IRB, and have a very low IRC output. This means that even though there is some heat output from the CHE, there is little to no long wave infrared radiation reaching objects in the tank for heat to be released while light sources are off.
Deep Heat Projectors (DHP)
Deep heat projectors are similar to a CHE in that they do not emit visible light, however they are a stronger heat source. DHPs emit IRC and can effectively increase ambient temperatures in an enclosure, while also emitting some IRB and IRA waves. The amount of IRA released is not nearly as strong as what is released by a basking light and cannot be used in place of one, but is a great addition to a basking zone or to keep enclosures warm during the night. Since they release more IRC, objects located under the DHP will be able to store and release more warmth.
UVB
UVB bulbs, which produce visible light and wavelengths in the ultraviolet spectrum, are not a heat source. However, UVB lights should be placed near the basking zone to allow captive reptiles to properly synthesize vitamin D (learn more about UVB).
Summary
Given the importance of the sun for the survival of reptiles, one of the main goals of reptile husbandry should be to mimic the sun as closely as possible based on currently available technology. Using a variety of heat and light sources allows for a better replication.
Wavelength | Natural Sunlight | Halogen Bulb | DHP | CHE |
Visual Light | 44% | 11% | N/A | N/A |
UV | 8% | N/A | N/A | N/A |
IRA | 32% | 39% | 8% | N/A |
IRB | 14% | 39% | 48% | 1% |
IRC | 2% | 12% | 44% | 99% |
* These numbers are the average output of each heat source, percentages for artificial sources can range by manufacturer
The table above shows how much of each wavelength is output by the following heat sources. As shown, halogen bulbs are the most well-rounded heat source, and CHE provide the least amount of variety in their output.
To best imitate natural sunlight, pairing a basking bulb with a DHP will recreate the warmth of the sun and allow more IRC to be stored in surfaces around the enclosure. Adding in a UVB bulb will provide the ultraviolet waves needed to maintain the health of the reptile, while also aiding in creating more of their visible light (many reptiles are capable of seeing in to the ultraviolet spectrum). Many keepers have started to include LED full spectrum bulbs to further replicate the natural light spectrum reptiles would experience in the wild. Although LEDs are not necessary, they can be beneficial to help provide a day/night cycle for your reptile and provide them with more opportunities to see the world. If you are interested in adding live plants to the terrarium, an LED full spectrum bulb is required to allow the plants to grow.
Diurnal reptiles or basking species will clearly make use of this set up, but this does not mean that trying to replicate the sun isn’t necessary for nocturnal species. Many nocturnal species can still be caught cryptic basking, or sometimes fully basking in the early morning hours before they go to sleep. If they don’t cryptic bask during the day, they will still benefit from the IRC waves that are released by laying on a piece of rock that was warmed up during the day, or may bask under the night time heat source if provided with a DHP.
Although trying to recreate the sun may have seemed like a daunting task at the beginning of this article, after seeing how various available bulbs can work together shows that it is attainable. Overhead heating offers captive reptiles the opportunity to experience warmth that gives them the energy to explore their enclosures and carry out their natural biological functions. Any heat sources selected should be paired with a thermostat to prevent the reptile from overheating or being potentially burned.
References: