Heat vs UVB

As we’ve mentioned in some of our other posts, the most common thing that comes to mind when people think of reptiles is that they’re ectothermic. Most people refer to “ectothermic” as “cold-blooded,” but this term isn’t really accurate. To put it simply, reptiles don’t have cold blood. However, their body temperatures will cool down if the ambient (air) temperature is cool, and their body temperatures will warm up if the ambient temperature is warm. Many people also think that reptiles (ectotherms) can’t manage their own body temperatures on their own and that it’s solely dependent upon the ambient temperature. This, however, is also untrue. Reptiles can manage their body temperatures, but over a much wider range than mammals (endotherms). They’re able to influence how much heat is exchanged between themselves and the environment (with varying ability).

What doesn’t often come to mind for new and beginner-level reptile owners, is UVB. Ultraviolet light rays are also very important for your reptile’s health, as they would naturally be supplied by the sun in addition to heat. Moreover, there are different types of UV light and ways to measure them:

  1. Ultraviolet-A (UVA) refers to light wavelengths that allow reptiles (and us) to use our vision and see things.
  2. Ultraviolet-B (UVB) refers to light wavelengths that penetrate the skin of reptiles and activate vitamin D within their bodies (and what is responsible for tanning our skin).
  3. Ultraviolet-C (UVC) refers to light wavelengths that have sanitizing (germicidal) properties.
  4. Ultraviolet index (UVI) is a measurement of UVB wavelengths that contribute to vitamin D synthesis (note that not all UVB wavelengths are involved with vitamin D synthesis!).
    • UVI is a different measurement than UVB, and each requires its own type of meter. Measuring UVI will supply values from 0.0-7.0, and measuring UVB will supply values from 280-315. Measuring UVI will provide a reading of how much vitamin D–synthesizing UVB your reptile is receiving!
Illustration courtesy of Klaran University (Green Island, NY).

There’s so much we could talk about regarding reptiles, heat and UVB. But this post will focus on how you can supply heat and UVB to your reptile in your home, making sure that it’s safe for them and for you!

How to Provide Heat

  1. Provide an appropriate size heat bulb for your reptile. In very general terms, you will need a smaller size (lower wattage) heat bulb for tropical species and smaller terrariums, yet a larger size (higher wattage) heat bulb for desert species and larger terrariums. However, what is considered a “small” or “large” terrarium can be relevant, so check in with The Repstylist if you have questions about providing the right heat bulb!
  2. Provide the appropriate type of heat bulb for your reptile. Heat bulbs can be light-emitting or non light-emitting, infrared, halogen, basking, and more.
    • Light-emitting heat bulbs aid in simulating and adding daylight; non light-emitting heat bulbs are good nighttime, secondary or 24-hour heat sources.
    • Infrared heat bulbs produce a red light, which is a good nighttime, secondary or 24-hour heat source.
    • Halogen heat bulbs provide a “whiter” (rather than “yellow”) light.
    • Basking heat bulbs have more narrowly directed heat emission to keep heat directed toward one spot as opposed to radiating outward.
  3. Provide a temperature gradient along your reptile’s terrarium. This means having a cooler side and a warmer side, which will allow your reptile areas to cool off or warm up (they know when they need to do either). You can create a temperature gradient by placing the heat lamp(s) on one end of the terrarium. As tempting as it may be, avoid placing the heat lamp in the middle of the terrarium.
  4. Provide a basking (hot) spot that is significantly warmer than the warm side of the terrarium. Create the basking spot on the warm side of the terrarium by placing an item, such as a branch, so that it’s elevated toward the heat source. Since the elevated end of the branch will be closer to the heat lamp than the floor of the terrarium, it will be significantly warmer. This, again, allows the reptile to bask under imitated direct sun exposure with the option to cool off in other areas of the terrarium.
  5. Measure the temperature supplied by the heat bulb (we recommend using a digital thermometer with a cord and probe for measurement, as you can easily move the probe to any spot in the terrarium). Each reptile species has an ideal range of daytime, nighttime, and basking spot temperatures.
    • Place the probe on the highest point of the basking spot and take a measurement.
    • Place the probe on the floor of the terrarium directly under (or as close as possible) the heat bulb and take a measurement.
    • Place the probe on the floor of the cool side of the terrarium and take a measurement.
    • You should see a decrease in temperature as you take the measurements in this order. Compare these numbers to the appropriate temperature ranges (basking and daytime) for your reptile’s species. Make adjustments to the height of the heat bulb as necessary.
      • Consider that you may need to raise the heat bulb in order to obtain the right temperatures. You can do this by using a lamp stand.

How to Provide UVB

  1. Provide a UVB bulb of appropriate strength for your reptile and its terrarium size. UVB bulbs typically come in “5.0” and “10.0” strengths. These numbers refer to the amount of UVB output that will contribute to vitamin D synthesis for your reptile (either 5% or 10% of the UVB wavelength output). In very general terms, the 5.0 bulbs tend to work best for smaller terrariums and tropical species, while the 10.0 bulbs tend to work best for larger terrariums and desert species. However, what is considered a “small” or “large” terrarium can be relevant, so check in with The Repstylist if you have questions about providing the right UVB bulb!
  2. Provide a UVB gradient along your reptile’s terrarium. Much like a temperature gradient, this means having one side of the terrarium with little-to-no UVB exposure, and the other side with high UVB exposure. To do this, place the UVB bulb on the SAME side of the terrarium as the heat lamp. In nature, UVB and heat both come from the sun, which means when setting up your reptile’s terrarium, these sources should be together (imitating sun exposure).
  3. Measure the UVI supplied by the bulb you’ve chosen. Each reptile species has an ideal UVI value (or tight range of values).
    • Hold the UVI meter with the sensor as close to, and level with, the basking spot to get a reading for the highest amount of UVB exposure your reptile can get.
    • Next, stand the UVI meter on the floor of the terrarium, directly underneath (or as close to as possible) the UVB bulb to get another reading.
    • Finally, stand the UVI meter on the floor of the cool side of the terrarium and take one more reading.
    • You should see a decrease in the UVI reading as you take the measurements in this order. Compare these numbers to the appropriate UVI for your reptile’s species. Make adjustments to the height of the UVB bulb as necessary.
      • Consider that you may need to raise the UVB bulb in order to obtain the right UVI. You can do this by using a lamp stand.
Illustration of proper heat and UVB source placement to create a gradient. Colors illustrate decreasing heat and UVI as you move away from the sources. Illustration courtesy of The Repstylist. All rights reserved.

The above information is meant to help you provide an appropriate main heat and UVB source for your reptile. You may find that a particular heat bulb that provides the right basking temperature doesn’t provide enough heat to keep the cool side of the terrarium “cool,” as opposed to “cold.” In this case, you can add a secondary heat source to the cool side of the terrarium, using a smaller size (lower wattage) infrared or non light-emitting heat bulb (dependent upon your reptile’s specific habitat).

As always, if you have questions about this topic, contact us here or at therepstylist@gmail.com!

©Copyright 2020 The Repstylist. All Rights Reserved.

6 Comments on “Heat vs UVB

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