HVR&R Reptile Heating and Lighting Guide
Heating and lighting go hand-in-hand when keeping reptiles, and is an extremely important aspect of reptile husbandry. In this guide, we will walk through the differences between various light and heat sources and discuss their benefits and downsides. An important thing to understand is there are two main lighting aspects in the reptile world - visible and non-visible light. Non-visible light is a type of electromagnetic radiation (EMR) that we cannot see. Infrared and ultraviolet are the two types of non-visible light that are important to understand when keeping reptiles.
Types of Light
The wavelength of EMR determines the type of light emitted by your light or heat source. The three spectrums we need to worry about are infrared, visible, and ultraviolet. Infrared light has the longest wavelengths, followed by visible light, followed by ultraviolet.
Infrared light is typically associated with heat. There are three types of infrared heat that we will discuss in detail later. Infrared has the longest wavelengths and precedes red on the visible light spectrum.
Ultraviolet light is associated with Vitamin D production. Ultraviolet light has three types which we will discuss in detail later. It has the shortest wavelengths, and follows after purple in the visible light spectrum.
Applying Species-Appropriate Heating and Lighting
Necessity of Species-Appropriate Temperatures
Unlike humans, almost all reptiles are completely dependent on their environment to manage their body temperature. The reason different species need to be kept in different temperatures is because their bodies are adapted to varying temperatures. Reptiles do not have a way to heat or cool themselves outside of their environment (with the fascinating exception of some Tegu species during certain parts of the year!) and are completely reliant on their keeper to provide appropriate temperatures for them.
An often overlooked necessity for reptiles is a thermogradient in their enclosures - meaning one side of the enclosure is warmer than other. This will allow your reptile to move as needed from warm to cool areas to regulate their body temperature. Having your reptile in an environment that is one temperature, even if that temperature is within their range, will not allow your pet to regulate its body temperature appropriately. There are numerous reasons an appropriate temperature is so imperative:
Regulating their metabolism
Supporting digestive health
Supporting the immune system to fight infections
Managing dormant parasite levels (almost all reptiles have them)
Maintaining their circadian rhythm
For females - incubating their offspring
This is not a complete list but covers a lot of the important points.
All reptiles should be kept on a consistent 12 hour light cycle - meaning the light is on for 12 hours, then off for 12 hours. This 12 hour rule applies to diurnal (awake during the day,) nocturnal (awake during the night,) and crepuscular (awake at dawn and again at dusk) animals.
Some people are led to believe that a nocturnal animal should never have a light source. But, how would you, as a diurnal human, feel if you had light 24/7? It would disrupt your circadian rhythm and havoc would ensue! We do not want havoc. No chaos here! All reptiles need a 12hr on/12hr off cycle to sustain their natural circadian rhythm.
A common item marketed to reptile keepers are red or blue “night lights.” These lights offer no benefits to your reptile and actually harm them! It disrupts their day/night cycle by having lights on at night, and the colors can damage their eyes. Rule of thumb; avoid colored lights.
The Importance and Controversy of Providing UVB Light
Ultraviolet light comes in the form of UVA, UVB, and UVC. UVA is the lowest energy, longest wavelength ultraviolet. UVA light is visible to reptiles, it’s a color that humans cannot see. It promotes breeding behavior and encourages diurnal movement. UVC is the shortest wavelength, highest energy ultraviolet wavelength that is not required by reptiles but does have antibacterial properties. The main concern here for reptiles is UVB.
At its core, UVB, a form of ultraviolet light, allows for the production of vitamin D3 in a reptiles' body. When combined with heat vitamin D is converted to vitamin D3, which is a primary mechanism for metabolizing calcium. Calcium is an essential component of bone health, among other bodily necessities.
The level of necessity to provide UVB for reptiles varies from absolutely required to simply beneficial. This is where the controversy lies. We at Hudson Valley Reptile & Rescue are of the belief that all reptiles benefit from UVB light, but it is not imperative for all species to do well in captivity. We do believe in providing the absolute best lives possible for our captive reptilian friends, however, and do promote UVB for species even where it is not strictly necessary.
With regards to UVB for reptiles - the question should not be “why?”. It should be “why not?”.
Metabolic Bone Disease
Let’s get into why UVB is undeniably required for certain reptiles. Animals such as bearded dragons, savannah monitors, chuckwallas, red-eared sliders, uromastyx, and many others will develop Metabolic Bone Disease - MBD - without appropriate UVB lighting. Metabolic Bone Disease is a permanent and irreversible condition caused by calcium and Vitamin D deficiencies. It causes skeletal deformities that vary in severity based on the extensiveness of the condition. Reptiles affected by MBD may have misshapen skulls, legs, spines, and more. Reptiles who suffer from this condition often have trouble with mobility, struggle to eat, and have difficulty live enriched lives. It is also a notably painful condition.
Please note - the absence of appropriate UVB exposure is not the only cause for MBD, but it is the most prevalent.
Benefits of UVB For All Species
There has been extensive research that indicates all reptiles benefit from UVB exposure. Vitamin D production is promoted by UVB exposure and is an essential vitamin for metabolizing calcium. Although snakes are not typically thought to benefit from UVB because they have adapted to getting the vitamin D they need from their food, studies have shown that snakes that were provided UVB had higher levels of vitamin D in their blood. Vitamin D plays an essential part in brain, circulatory, digestive, excretory, and immune systems. Vitamin D also promotes healthy beta-Endorphin systems, which involve behavioral stability, bodily stress, and more. Ongoing research has shown that UVB exposure also benefits the eyesight, breeding, and overall mental wellbeing of reptiles.
UVB For Nocturnal Species
There are people who push the idea of nocturnal species not benefiting from UVB light in any way. However, there are numerous sources that indicate reptiles will cryptic bask. Cryptic basking is when an animal will hide most of its body, but leave an appendage - usually a tail - exposed to sunlight to absorb UVB. An important distinction is that nocturnal animals may be more active at night, but they are not photophobic. Nocturnal animals can be active during the day at times, or cryptic bask.
A quick but important note:
Some animals with certain color mutations (morphs) are more sensitive to UVB exposure. Think of it like the Irish person you know who gets sunburned way too easily. Morphs that are especially sensitive to UVB may include albino, their derivatives, and more. Please research your specific animal’s morph when making the decision on how much UVB to provide.
The Quest to Replicate Sunlight
The sun produces all three types of light mentioned above; infrared, visible light, and ultraviolet. The goal as a reptile keeper is to reproduce the types of light created by the sun in a way that suits the species you are keeping best. The sun’s light, by the time it reaches Earth, is made up of the approximate percentage displayed in the graph shown here.
We've covered Ultraviolet, we all know about visible light, let's get into the biggest chunk of sunlight - infrared.
Heat and Infrared Light
Infrared light is invisible to the human, and reptile, eye. The importance of infrared light in the reptile context lies in its association with heat. Although heat seems very straightforward, and to an extent it is, let’s deep dive into the types of infrared heat so you can give your reptile the best life you can!
If you read the article up to this point, you will have seen the term UVB. UVB is a subset of ultraviolet light, the others being UVA and UVC. UVA and UVC are not as essential to reptiles as UVB is - though they can see UVA as a color invisible to humans! The same concept applies to infrared, there is IR-A, IR-B, and IR-C. IR-A is the highest in energy, and its heat penetrates the animal’s tissue the furthest. IR-C is the lowest in energy and provides the most superficial heating. IR-B falls in the middle.
One type of infrared heat is not necessarily better than any other, and instead the goal should be to replicate the sun’s infrared production as closely as possible. Using this graph, we can see that a majority of the sun’s heat is IR-A, or the deepest-penetrating type of infrared heat.
Let’s go over the big players in the overhead heating game, and see how they compare to sunlight.
Types of Heating for Reptiles
The three most popular types of overhead heating are PAR38 Halogen bulbs, Deep Heat Projectors (DHP,) and Ceramic Heat Emitters (CHE.) PAR38 Halogen bulbs provide infrared in the closest ratio to that of sunlight, and include IR-A, IR-B, and IR-C. Halogen bulbs also produce visible light which make them a great daytime heat source.
Deep Heat Projectors produce all three types of infrared heat, but lower amounts of deep-penetrating IR-A than halogen bulbs. However, DHPs do not produce visible light which makes them a great option for a supplemental heat source. Ceramic Heat Emitters are similar to DHPs in that they do not produce visible light, however the heat they produce is almost exclusively shallow-penetrating IR-C. CHEs produce very small amounts of IR-B, and zero IR-A. CHEs are generally less expensive than DHPs, so they may be a more economical option, but DHPs are almost universally superior.
All reptiles should have lower temperatures during their night cycle (no visible light.) However, if you find their environment gets too cold, adding a DHP or CHE to keep their temperatures within their safe range is a great option.
Under-tank heat (UTH) comes in the form of heat mats. They are commonly recommended items for numerous reptiles. Heat mats only provide IR-C. Certain species requiring “belly heat” is a long debunked myth that is still promoted by many pet stores, companies, and other keepers. We do not encourage the exclusive usage of UTH because it only provides IR-C. Heat rocks and similar should be completely avoided for a different reason; they are dangerous due to the likelihood of severely burning your reptile.
To summarize; Halogen bulbs provide the closest replication to sunlight. They produce visible light and infrared heat as the sun does, and the percentages/ratios of each are comparable. DHPs are a great supplemental heat source that provides comparable amounts of IR-A to the sun, but do not produce visible light. CHEs are an economical option to provide supplemental heat and no visible light, but are inferior to DHPs. DHPs and CHEs are good supplemental or, if needed, nighttime heat options. None of these bulbs, however, produce UVB like the sun does - which will be covered in another section. We do not recommend exclusive usage of heat mats because they only produce the most shallow-penetrating heat.
What Heat Bulb Should You Buy?
Now that we have a good understanding of the types of overhead heat, let’s go over what you should purchase.
The two primary parts of every lighting and heat source are the bulb and the fixture. The fixture provides electricity to the bulb and illuminates it. It is essential that your bulb and fixture are compatible. In the specs list below, we will highlight the important specifications that need to match.
There can be an overwhelming number of specs listed on most heat sources, so let’s break it down and make it more digestible!
Wattage (W) - think of this as how strong the heat source is. The higher the wattage, the more heat it will produce.
Note: it is absolutely imperative that your fixture (hood, etc.) is rated for an equal or higher wattage than your bulb is, you are safe. A 75W bulb in a 60W fixture is a recipe for a fire.
When using a dimming thermostat, you want the lowest wattage halogen bulb possible that still achieves the desired temperatures. This is because when the halogen is dimmed, its spectrum can change. A halogen's spectrum at 100% power is closest to the sun.
PAR - specific to the recommended halogen bulbs, PAR is essentially how far the light spreads; think a spotlight versus a flood light. PAR38 is a great option for most reptiles. It provides a good amount of spread, but enough concentration that they can comfortably bask.
The PAR number must match the fixture
Voltage (V) - this is the operating voltage of your bulb.
The voltage of your bulb must be compatible with your fixture
Please note - we cannot provide the exact specs for your specific application. There is a lot of variation that must be taken into account such as species and desired temperature, ambient temperature of your home, size and material of the enclosure, and more.
What UVB Bulb Should You Buy?
There are three types of UVB bulbs that are marketed towards reptiles. To make it easy: one is dangerous, one is all around an inferior bulb, and one is the type you should buy.
Mercury vapor bulbs are the dangerous choice. They can be utilized correctly but require a lot of knowledge and experience, and we discourage use of them. Mercury vapor bulbs are unique in that they produce all three types of light - heat, visible, and ultraviolet in the form of UVA and UVB. At first this may seem like an asset, however, it eliminates the control you have as to how much heat versus ultraviolet versus visible light goes into the enclosure. Each of those are a set amount, and that amount is usually not ideal. The light produced is also very concentrated and can cause burns to your reptile if it isn’t placed correctly. In addition to the lack of control of each type of light, mercury vapor bulbs are being phased out by most manufacturers because of their tendency to explode. Mercury is very toxic, and when the bulb explodes the mercury is difficult to contain and safely clean for disposal.
Coil UVB bulbs are the inferior bulb choice. Like the mercury vapor bulbs mentioned above, the light coil UVB bulbs produce is very concentrated and can cause burns to your reptile. The amount produced by these bulbs is also too low to meet the UVB requirements of most species.
Strip-style UVB bulbs are the type of bulb you should buy. Strip-style UVB bulbs come in a variety of strengths to suit any species’ needs. The strip-style UVB bulbs spread the UVB across a wider area too, eliminating the burn issue caused by over concentration in the other two bulbs.
Types of Strip-style UVB Bulbs
There are two strip-style UVB bulbs appropriate for reptiles; T5 and T8. T5 produces more intense rays than T8 bulbs. T5 UVB rays can penetrate some mesh screen lids. In general, T8 bulbs must be mounted inside the enclosure to have the desired effect because they are not powerful enough to penetrate screens. The strip-style UVB should overlap with the heat (basking) bulb.
The two main aspects of UVB to be concerned about are the strength of the bulb and the distance between the bulb and the basking spot. Each manufacturer is different and it is important to compare specs between manufacturers.
A good frame of reference is the Ferguson scale referenced earlier in this guide. With the same bulb, a species listed in Zone 3 will need the bulb closer to them than a species in Zone 1. There is a tremendous amount of variation in UVB bulbs based on the manufacturer. Any reputable bulb manufacturer will list the recommended bulb strength and distance from the basking spot the bulb should be.
Ultraviolet Light Requirements and the Ferguson Scale
The third and final piece to providing reptiles the closest thing to natural sunlight is providing UVB. With infrared, visible light, and ultraviolet light all being provided in appropriate doses, you are giving your reptile the closest thing you can to the natural light that allows them to thrive.
The amount of UVB needed varies from species to species. A good starting place for determining how much UVB to provide each species is using the Ferguson scale. Dr. Gary Ferguson created four levels based on desired UV Indexes (UVI) of different species. Zone 1 has the lowest UVB requirement, and Zone 4 has the highest. Some quick examples of species from each zone are:
Zone 1 (Crepescular or Shade Dweller) - Zone range UVI 0 – 0.7
Zone 2 (Partial Sun or Ocassional Basker) - Zone range UVI 0.7 – 1.0
Ball (Royal) python
Eastern box turtle
Everglades rat snake (and most other rat snakes)
Zone 3 (Partial or Open Sun Baskers) - Zone range UVI 1.0 – 2.6
Bearded dragon (some studies have them in Zone 4)
Black and white tegu
Zone 4 (Mid-day Sun Basker) - Zone range UVI 2.6 – 3.5
Bearded dragon (some studies have them in Zone 3)
Savannah (Bosc) monitor
Some species may fall somewhere in the middle of two zones. These are only guidelines.
We have covered a lot here! We always encourage everyone to do additional research outside of this guide, but we hope you found it helpful. Heating and lighting is such an important part of reptile husbandry, and we hope this guide pushes a higher standard of care and more scientific-based practices that will benefit your reptiles.