UVB Lighting for Reptiles: Simplifying the Science

May 26, 2017

UVB Lighting for Reptiles: Simplifying the Science

While may aspects of reptile husbandry are fairly straightforward, lighting is often a subject that causes keepers considerable confusion.

This is especially true for those who must provide ultraviolet light to their pets, and many keepers are unsure of the best way to care for their critters. Myth and misinformation abound, which often leads to suffering pets and heart-broken keepers.

The fact is, most diurnal lizards and turtles (those who are active during the daytime) have very specific lighting requirements, which keepers must address through their housing and husbandry practices. The scientific and veterinary communities are still working out the fine details regarding ultraviolet light and reptiles, but the basic mechanisms at play are relatively well understood.

Fortunately, keepers have devised several methods for providing the proper lighting for the most commonly kept reptile species.

The Electromagnetic Spectrum

To understand how to provide your pet lizard or turtle with the proper lighting, you’ll need to start by learning a little bit about light.

Light is a type of energy scientists call electromagnetic radiation. This radiation occurs at a variety of different wavelengths; our eyes recognize some of these different wavelengths as colors. However, our eyes are only sensitive to a tiny fraction of the entire electromagnetic spectrum. In fact, there is plenty of “light” we can’t see.

The Electromagnetic Spectrum

Visible light has wavelengths ranging from about 400 to 700 nanometers – everything you can see is either emitting or reflecting energy in this range. Longer (“redder”) wavelengths take the form of infrared energy, microwaves and radio waves, while shorter (“bluer”) wavelengths include ultraviolet light and X-rays.

It is the wavelengths that are slightly shorter than those of visible light that are important from a reptile-husbandry point of view. Called the ultraviolet portion of the spectrum, these rays are further divided into three subranges, designated A, B and C. When referring to one of these subdivisions, they are called UVA, UVB or UVC.

UVA is generally defined as light with wavelengths between 320 and 400 nanometers, while UVB is comprised of light with wavelengths between 320 and 280 nanometers. UVC, which is dangerous and not produced by most commercial lightbulbs designed for reptiles, has wavelengths varying from 280 and 180 nanometers.

anole parietal eye.

The sun produces plenty of light in these ranges, humans just can’t see it. However, many animals can see UV light – including many lizards and turtles. In fact, many heliothermic (sun-loving) species can detect these wavelengths via a parietal eye, recognizable as a small, unusually colored spot on the center of the head.

As it turns out, there’s a good reason they can detect this kind of light.

Vitamin D and Calcium

When lizards and turtles bask in the mid-day sun (or a lamp that produces light between 290 and 315 nanometers – part of the UVB portion of the spectrum), their bodies produce Vitamin D3. Among other things, D3 plays a role in the metabolism of calcium. Without enough D3, reptiles cannot effectively use the calcium obtained through their diet.

Calcium is necessary for a variety of different bodily processes, and when a lizard or turtle is unable to properly use its calcium, a variety of health problems can occur. Eventually, this lack of useable calcium will cause the lizard to draw the mineral from its bones. This can cause significant pain, lead to deformities, ruin your pet’s quality of life and ultimately prove fatal.

Some Reptiles Need UVB; Some Reptiles Don’t

Not all reptiles require UVB lighting, as they have apparently evolved other production pathways. But fortunately, it is usually fairly simple to distinguish those species generally regarded as requiring UVB from those that do not appear to require it.

Reptiles That Require UVB Lighting

Most diurnal lizards, turtles, and crocodilians require UVB lighting. Those that live in tropical latitudes and wide-open habitats tend to require more than those living under a forest canopy or farther from the equator do.

This includes popular pets like:

  • Bearded dragons (Pogona vitticeps)
  • Sulcata tortoises (Centrochelys sulcata)
  • Greek tortoise (Testudo graeca)
  • Green iguanas (Iguana iguana)
  • Red-eared sliders (Trachemys scripta elegans)
  • Collared lizards (Crotaphytus spp.)
  • Panther chameleons (Furcifer pardalis)
  • Veiled chameleons (Chamaeleo calyptratus)
  • Anoles (Anolis spp.)
  • Uromastyx (Uromastyx spp.)
  • Blue Tongue Skinks (Tiliqua spp.)*
  • Monitor Lizards (Varanus spp.)*
  • Tegus (Tupinambis spp.)*

* Some keepers do not provide UVB lighting for these species, but it is better to err on the side of caution whenever there is conflicting information about a animal's UVB needs. 

A green iguana.

    Reptiles That Do Not Appear to Require UVB Lighting

    Although there are a few snakes that may benefit from UVB lighting, most commonly kept snakes have been maintained for multiple generations without special lighting. In fact, breeders maintain most commonly kept snake species in drawer-style systems, which only receive incidental room lighting.

    This includes both nocturnal and diurnal species, such as:

    • Ball pythons (Python regius)
    • Boa constrictors (Boa constrictor)
    • Gray banded kingsnakes (Lampropeltis alterna)
    • Amazon tree boas (Corallus hortulanus)
    • Emerald tree boas (Corallus caninus)
    • Green tree pythons (Morelia viridis)
    • Carpet pythons (Morelia spilota)
    • Rosy boas (Lichanura spp.)
    • Kingsnakes (Lampropeltis spp.)
    • Rat snakes (Pantherophis spp.)

    In addition to snakes, most nocturnal lizards are able to satisfy their Vitamin D needs through dietary means. This includes:

    • Leopard geckos (Eublepharis macularius)
    • Fat-tailed geckos (Hemitheconyx caudicinctus)
    • Leaf-tailed geckos (Uroplatus spp.)
    • Tokay geckos (Gekko gecko)
    • Crested geckos (Rhacodactylus spp.)

    Chameleon UVB Lighting

    Methods for Providing Ultraviolet Light

    There are essentially four different ways to provide your reptile with ultraviolet light. Some of these methods and strategies are easier than others, and some are more effective than others, so you’ll need to consider all the possibilities before deciding on the best approach for you and your pet.


    The sun provides a significant amount of UVB during the middle of the day, and it does so relatively reliably and for free. Unfiltered sunlight also provides basking reptiles with wavelengths in the UVA portion of the spectrum, which can help encourage natural behaviors (especially breeding behaviors).

    However, because most reptile keepers maintain subtropical or tropical species, it is rarely practical to maintain your pet outdoors. Unless you live in Florida or the southwestern United States, you’ll likely need to bring your pet inside for the winter, thereby forcing you to purchase and maintain two separate habitats. Additionally, outdoor maintenance presents a host of other problems, such as protecting your pets from predators and inclement weather.

    Linear Fluorescent Lights

    Most good linear fluorescent lights designed for reptiles produce very little heat, a relatively nice color spectrum and a modest amount of UVA and UVB. However, it is important to note that different products produce varying amounts of UVB light – you have to match the light to your reptile’s needs.

    For example, the Flukers Repta-Sun 5.0 UVB Lamp won’t produce enough UVB to keep your bearded dragon or Iguana healthy, but they are a great choice for your box turtle (Terrapene carolina), panther chameleon or basilisk (Basiliscus spp.) enclosure.

    Conversely, the Zoo Med REPTISUN 10.0 UVB Bulb produces approximately twice as much UVB as the Flukers model, and is a great choice for bearded dragons, iguanas and uromastyx lizards.

    Compact Fluorescent Lights

    Compact fluorescent lights provide a similar quality of light as their linear counterparts, but they can be used with a reflector-style fixture. In this category, the Exo Terra Reptile UVB200 HO Bulb is the light by which all others are measured. It provides more UVB than is necessary for reptiles that live under forest canopies, but your desert-dwelling lizard or tortoise will appreciate it greatly.  

    Mercury Vapor Bulbs

    Mercury vapor bulbs not only produce a significant quantity of UVB light, they also produce quite a bit of heat, further distinguishing them from fluorescent lights. They are the light of choice for reptiles who need copious amounts of UVB yet also require very warm basking spots (such as bearded dragons and other desert-dwelling herps).

    However, while mercury vapor bulbs are prized for their ability to produce a ton of UVB, they do have a small downside: They typically produce far too much heat for a very small enclosure. Nevertheless, when you really need to replicate the sun as best you can, you’ll need something like the Exo Terra Solar Glo Mercury Vapor Lamp.

    A pair of painted turtles.

    Safe and Proper Use of UV Lights

    It doesn’t matter how awesome a light is if you do not use it properly. Always follow the manufacturer’s instructions, but you’ll also want to follow the proceeding guidelines:

    • Remember that while it is important to create a basking “spot,” this does not mean that highly focused spot bulbs are the best way to do so. Generally speaking, you want the basking spot to accommodate the reptile’s entire body, rather than cooking one small spot (and always use a good thermometer to monitor the enclosure temperatures).
    • Never place UV-producing bulbs or fixtures on the side of an enclosure. Most sun-loving reptiles have evolved thick ridges above their eyes to shield them from the sun. But these ridges do not protect the lizards’ eyes from the side, so placing lamps at odd angles can harm their eyes.
    • Be sure that the distance between the bulb or light fixture and your reptiles is at least 6 inches, but no more than 18 inches. In most cases, it is probably best to aim for a 12-inch-gap between your pet and the bulb.
    • Never look directly into a UV-producing light. It is also important to ensure that the lamp or bulb you are using are not within the sightlines of young children or pets.
    • Understand that even the best bulbs produce less UVB over time, so you’ll need to replace them periodically. Most manufacturers will recommend a suitable replacement schedule, which is generally between 6 and 12 months.
    • Never bathe the entire enclosure in UVB light; your pet should always be able to avoid the light if so desired. Realize that your mercury vapor bulb is pumping out UVB for 12 hours a day – the sun only produces an appreciable amount of UVB for a small portion of the day, even at tropical latitudes. So, give your lizard some type of shade, under which he can hide from the light.
    • If you are using a combination of an incandescent bulb for heat and a fluorescent bulb to provide ultraviolet light, be sure that they illuminate the same area. Lizards and turtles bask to absorb UV-light as well as heat; accordingly, you’ll want to make sure that the basking spot provides both. Combo light shrouds – like the Zoo Med Combo Deep Dome -- make this easier, and they are often available as complete kits – like the Zoo Med Tropical UVB & Heat Lighting Kit.

    A bearded dragon.

    Providing proper lighting is an important part of reptile husbandry, but it needn’t be confusing. Just research the needs of your specific pet, consider his or her range and natural habitat, consult with your veterinarian, and select the best UVB light you can.

    You’ll be glad you did, and so will your pet.  

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