Understanding UV: Why Reptiles Need It and How It Works

Understanding UV: Why Reptiles Need It and How It Works

Keeping reptiles is a lot different than keeping dogs or cats, from personality to care requirements. One of the elements that reptile hobbyists need to keep in mind is UV lighting. Reptiles rely on this critical light wavelength to process nutrients and lead happy lives—and it’s up to their owners to provide them with exactly what they need. But what is UV lighting, and how can we know whether we’re doing a good job of providing it? Do all reptiles even need it? Here’s an overview of UV lighting, from how it works to how you can incorporate it into your scaly friend’s habitat in a natural and effective way.

What Is UV Lighting?

UV lighting, also called ultraviolet light, is one type of light produced by the sun. Unlike the visible light produced by the sun (and most light bulbs), humans can’t see UV light because of its shorter wavelengths; it’s located immediately after purple in the rainbow. UV light is a type of radiation, and like other radiation, it accomplishes specific tasks when it comes in contact with living things.

We use microwave radiation to warm our food and radiation therapy to attack cancer cells, all because each wavelength can perform unique functions. In nature, the sun’s UV rays can be broken down into three subtypes: UVA, UVB, and UVC. Reptiles can see UVA light, which changes throughout the day and across seasons. This helps them regulate when to sleep and wake up, when to mate, and even when to eat. 

UVB light is invisible to reptiles, but it is absorbed by their skin and plays a crucial role in their metabolism. UVC light is produced in small amounts by the sun and can kill bacteria, which is how UV cleaners work. However, exposing reptiles to this kind of light in high quantities can harm them.

Do All Reptiles Need UVB?

Reptiles rely on both UVA and UVB exposure from the sun to regulate their lives in the wild. In captivity, they can face significant consequences without it—and especially without UVB. Lack of proper UVB exposure is one of the leading causes of MBD, or metabolic bone disease. While it’s true that MBD arises from an insufficiency of calcium, even reptiles that receive calcium-dusted food can suffer from this disease without sufficient UV exposure. The reason for this is how a reptile’s metabolism works.

When UV light hits a reptile’s skin, it is absorbed and turned into a vitamin D precursor that is sent to the liver for processing. There, it turns into vitamin D, where it makes a final stop in the kidneys to pick up some extra molecules and become 1,25(OH)2D, or calcitriol. 

Meanwhile, your reptile has calcium floating around in its intestines. However, its intestinal walls only let about 10% to 15% of calcium through. Think of these calcium molecules like large, awkward balls that don’t roll very efficiently. If calcitriol, created from UVB light, is in the area, it serves like a cart with wheels that picks up these awkward calcium molecules and speeds them into the intestinal wall very efficiently, increasing absorption multiple times over. 

Thus, even if your reptile is receiving a lot of calcium supplementation, they’re only absorbing a fraction of it without exposure to ultraviolet light and the vitamin D compounds created from it. Because of this, it’s recommended that reptiles have the option to bask under a UV light whenever possible. 

How to Provide UVB for a Reptile

Every reptile species has its own needs when it comes to UV light. That’s why it’s best to do research, not only about how experts keep your species, but also what kinds of conditions they experience in the wild. The most effective way to offer UVB (and UVA) light to a reptile is with a specialized bulb made to generate these wavelengths. Regular light and heat bulbs do not produce UV, and UV light does not pass through glass or plastic, so you’ll need to affix your UV lighting inside the enclosure or above a screen. 

For most enclosures, a UV strip such as a Reptisun T5 High Output lamp will provide comprehensive coverage with a small footprint. Most coil UV bulbs do not output adequate ultraviolet light to meet your reptile’s needs, but they may be used as a supplementary option. 

Measuring UVB

Once you’ve got a UV light installed, how do you know that it’s working? After all, humans can’t see UV rays. The tool for this job is called a solarimeter or pyranometer, which works by reading how strong the radiation is in the area. Keepers can use these tools to determine how far away their reptile should be in order to feel the effects of the UV bulb (most commonly, that’s about 12 to 18 inches), as well as whether their bulb is still outputting UV radiation. As an added benefit, UV lamps also function as light sources, so they can keep your enclosure bright and simulate natural daylight!

Other Considerations

Remember that reptiles encounter UV radiation in the wild in the form of sunlight. This means that they meet their UV needs during the day. Be sure to turn your ultraviolet lamp off according to the day-night cycle so that your reptile can maintain a healthy circadian rhythm. 

Additionally, place your UV light near the basking lamp. Heat assists in the metabolism of vitamin D and calcium, improving outcomes for reptiles that utilize UV. If you have a shade-dwelling species, ensure that they have options to get away from the ultraviolet light, whether through hides, burrows, or leaf cover. Avoid placing a UV light on the side of an enclosure, as the bright light horizontally aligned with a reptile’s eyes can cause vision damage over time.

UV bulbs don’t last forever, but what’s difficult is that they may still be producing light. Regardless of whether your UV strip has burned out, it is best to replace it every six months to one year. Over time, the ability of the bulb to output radiation on UVA and UVB spectrums decreases, even if the visible light is still on. If you have a solarimeter, you can measure to see whether your bulb is still effective. Otherwise, replacement is in order!

Back to blog

Leave a comment

Please note, comments need to be approved before they are published.