Understanding UVB

What is UVB?

UVB is part of the natural spectrum produced by the sun.

Why do animals need UVB? 

Many animals (most reptiles and birds) are able to utilize UVB to synthesize their own Vitamin D₃. While some species are able to get Vitamin D₃ from their diet (like snakes that eat whole prey items such as mice), most insectivores and herbivores must make D₃ of their own.

Vitamin D₃ is responsible for calcium metabolism, and if there is not enough circulating vitamin D₃ in the blood, animals are not able to use the calcium in their gut that comes from their food. Dietary calcium would then pass through the gut unused, and animals would be forced to take it from their bones, ultimately leading to a form of Metabolic Bone Disease (MBD).  MBD causes reptiles’ bones to become soft, resulting in severe deformities of the spine, broken legs and soft jaws. In severe cases, the internal organs can calcify and become hard—which can ultimately result in death. In addition to being a major component of bones and eggshells, calcium is involved in countless biological processes at the cellular level, including cell communication, muscle contractions and other functions that are essential to life.

In the early days of keeping reptiles, little was known about the specialized lighting requirements of the majority of reptile species. During this time, reptiles housed indoors were not exposed to UVB, and as a result, would often develop Metabolic Bone Disease (MBD).

For a more in-depth information about UVB and reptile lighting, read this article: https://zoomed.com/wp-content/uploads/EPREP1109_ReptileLighting.pdf

How do animals get UVB?

In outdoor habitats, animals receive their UVB from the sun. Indoors, however, a UVB source must be provided. Contrary to popular belief, placing a pet’s habitat near a window will not suffice, as household glass and plastics effectively filter out UVB. In addition, placing a glass terrarium in direct sunlight (including sunlight coming through a window) can be very dangerous. Glass terrariums can act as a greenhouse and trap heat, allowing the habitat to get far too hot to be safe for pets. NEVER PLACE A GLASS TERRARIUM IN DIRECT SUNLIGHT!

Facts to Remember:

• While UVB is important, more is not always better!
• Always follow the manufacturer’s guidelines.
• Use UVB lamps for 10-14 hours a day.
• Some reptiles have traditionally been thought to have no requirement for UVB, but research has shown that most will benefit from some (even low-level) exposure.
• Replace UVB lamps at least once a year.
  • Record the Date of First Use on the bulb
  • Use “UVB Reminder” at www.zoomed.com

Testing UVB

UVB can be tested in a few different ways.  In the past, use of a UVB radiometer allowed us to measure the number of microwatts per square centimeter of UVB were available in a given area.  One of the problems with this method was that the number that was read from an artificial UVB source could not be compared to that of the sun.  The portion of the light that was measured was too broad and because insufficient research had been done on how many microwatts each animal needed, the number was not terribly useful in determining the ability of animals to produce vitamin D3 with exposure to the light.

Recently, a UV Index Radiometer has been the ideal method of measuring UVB.

Current methods for UVB testing provide much more helpful information and allow us to choose the best source of UVB for each individual pet and habitat.

What is the UV Index?

Developed by the World Health Organization, the UV Index is a measure of the UV radiation from sunlight that contributes to vitamin D synthesis, as well as skin and eye damage. It is NOT simply a measure of total UVB, but instead measures only the specific UVB (and some UVA) wavelengths that are responsible for the biological processes mentioned above. Not all UVB wavelengths are equal in their ability to promote vitamin D synthesis. The UV index takes this into account, with each wavelength “weighted” differently depending on how effective it is at promoting vitamin D synthesis. The UV index is often given in weather reports and uses a color coded scale to indicate UV intensity.

How does the UV Index apply to Reptiles?

The UV Index was developed as a tool for evaluating human risk of UV exposure outdoors. So how do we use it to evaluate UV lamps designed for use with reptiles in terrariums? This question was approached scientifically by a team of researchers led by the prominent herpetologist; Gary Ferguson, Ph.D. In their study, they took UV Index readings throughout the day in locations where they observed different species basking outdoors in sunlight or living in the shade. Using these UV Index readings, they were able to make recommendations for appropriate UV levels by creating four different UV Index “zones.” These zones were named the “Ferguson Zones” by Frances Baines (one of the authors and noted reptile photobiologist). This research is ongoing and UV Index readings are constantly being recorded for new species. Thanks to a large community of professional and citizen scientists, we now have a better understanding of the UV exposure that our reptiles need to thrive!

Evaluating Lamp Safety

A major advantage of using the UV Index to evaluate reptile lighting is that readings can be compared to natural UV Index readings recorded in reptiles’ natural habitats throughout the year at times when reptiles are active. The highest UVI readings recorded at solar noon in summer in the deserts of the USA and Australia range from 14.0 to 20.0. At these levels, reptiles are not active and have retreated into burrows or the shade for safety. DO NOT attempt to achieve these levels in the terrarium at the basking site. It is unsafe for people to be outdoors without adequate skin protection at these levels. Research has shown that reptiles retreat from full sunlight when UVI levels are around 8.0 or higher. If a lamp produces UVI readings of 8.0 or higher at the basking site, then the lamp is unsafe and should be moved further away from the habitat or replaced with a different lamp. A lamp that is producing UVI readings of 8 or more at manufacturer recommended basking distances is unsafe and should not be used as this can result in illness, eye & skin damage, or even death. 

Zoo Med’s New Digital UV Index Radiometer can be used to determine if UVB lamps are producing safe and effective levels of UVB. This meter’s response curve is weighted to match the Vitamin D action spectrum to help ensure that pet reptiles are receiving proper and adequate exposure to UVB to help prevent and reverse Metabolic Bone Disease. This meter is easy to use and includes a quick reference scale to help determine the correct levels of UVB for various reptile species.