Many reptiles have specific needs when it comes to heat and light. Meeting these needs is essential to keeping these pets healthy, so it is important to understand why heat and light are so important.
The Importance of Heat
For all reptiles, providing appropriate temperatures is extremely important. Being ectothermic ("cold-blooded"—although they need warm temperatures) they rely on external temperatures to regulate their body temperature. In the wild, they naturally gravitate to an area with the temperature they need, moving into the sun or shaded areas as necessary. Therefore, a temperature gradient must be provided so that the reptile can choose the appropriate temperature as needed.
Temperatures must not be so high as to overheat the reptile. Just as important, however, is that temperatures not be too low since processes like digestion are only efficient at the right body temperature. At temperatures that are too low, a reptile may become sluggish and unable to digest its food properly.
For the reasons mentioned above, a gradient must be provided. Typically a basking light or other heat source can be placed at one end of the tank so that the temperature there is at the high end of the range for the reptile species. The other end should be maintained around the lower temperature range for the species.
However, providing the gradient isn't quite that simple. Depending on what sort of reptile you are housing, accessories should be placed in the tank in such a way that the reptile can use the gradient while behaving naturally. So, if your reptile likes to hide, some kind of shelter or hide should be provided in both the warm and the cool ends, so the reptile isn't tempted to hide all day in a shelter that is not at the optimum temperature. Similarly, if your reptile is arboreal, the appropriate temperatures must be available up in the branches that the reptile climbs on; the reptile can then thermoregulate and still be in its preferred location.
This may sound like a lot of trouble, but the key is to provide conditions that mimic what the reptile would find in its natural environment. Invest in a couple of good thermometers and regularly monitor the temperatures in different areas of the cage (especially where your reptile is spending a lot of time) and make sure the temperatures are correct. Remember the proper temperature is vital to your reptile's health!
Many captive reptiles do fine with a slight temperature drop at night (that is what many experience in the wild). Many reptile care sheets recommend a night time or minimum temperature. A slight gradient can still be provided, again to let the reptile choose where it wants to be.
There are several options for providing heat and the best one(s) for you will depend on your reptile and your enclosure. Overhead heating more naturally replicates a reptile basking in the sun, but under-tank heating is a good option to supplement the heat provided. If at all possible, avoid heat sources placed within the cage, or at least make sure they are shielded to prevent direct contact between the reptile and the heat source to prevent burns. This is particularly important for some species (e.g. iguanas and Chinese Water Dragons). Hot rocks should generally be avoided - often they can be hot enough to burn a reptile that rests on one, yet they do not do much for heating the whole tank. And of course, make sure all heating devices are used appropriately and safely to reduce the risk of burns or fires. A few options are presented below.
- Basking lights, spotlights, incandescent lamps: These represent a simple and effective way to provide heat as well as daytime light. They come in a variety of wattages and some experimentation may be necessary to find the right combination of distance and power to provide the right temperature. White bulbs can't be used 24 hours a day, though (your reptile needs some time in the dark too), so a dim colored bulb can be used at night. Nighttime bulbs made specifically for reptiles are a good choice. This type of heat is a nice choice since it provides a baking spot for your pet.
- Ceramic heating elements: These screw into a socket much light a bulb, but do not emit any light. They produce a lot of heat and must be used only in a ceramic socket rated for the element or there is a risk of overheating and fire.
- Under tank heating pads and tape: Human heating pads are okay but not ideal. Special heat pads and heat tape can be purchased for reptiles. These under tank heat sources are a good choice for supplementing heat provided by a basking light, or providing heat at night.
The Importance of Ultraviolet
Aside from the need for a regular day-night cycle, some reptiles need specific kinds of light, i.e. UV light. Similar to the requirement for heat, the requirement for UV light is vital for the optimal health of the species who require UV wavelengths. Even for those reptiles that do not need UV light, the provision of a regular day-night cycle is necessary. Without a regular cycle of light and dark, animals will experience stress. Additionally, if breeding is a goal, mimicking the changes in the light-dark cycle that would naturally occur as the seasons' change may be necessary to induce reptiles to breed.
Snakes and Nocturnal Lizards
Snakes, because they have evolved to eat whole prey, are pretty easy to feed and get virtually all their calcium and vitamin D needs through their diet.
Nocturnal species of lizards do not get much exposure to UV light in the wild, so do not have any special requirements for UV light producing bulbs.
Snakes and nocturnal lizards therefore simply need enough light to provide a day-night cycle appropriate for the species, and a regular incandescent bulb is fine. Bulbs used for heating and light are sufficient for these species.
However, many lizards and all turtles and tortoises need exposure to UVA and UVB light, which must be provided wither by regular exposure to sunlight or special lights.
Why Is UV Light Important?
Ultraviolet light (UV) is important in the production of vitamin D3, which is necessary for calcium metabolism. Vitamin D3 is produced in the skin with exposure to UV light (from sunlight). While vitamin D3 can be supplemented in the diet, it appears some reptiles, such as iguanas, make better use of vitamin D3 produced within their bodies than that provided in vitamin supplements. Sunlight is an impractical source of UV for most owners (UV light is blocked by glass, so exposure through windows is not a viable option). UV can be provided by special light bulbs.
The UV light is made up of UVA, UVB, and UVC wavelengths. UVC is harmful, and UVA and UVB are what the reptiles need. The most crucial consideration is the amount of UVB produced, and this is where the selection of an appropriate bulb is necessary.
Faced with a huge range of light bulbs in a pet store, there is sometimes confusion over which is the best kind to get. Make sure you get a full-spectrum light, that produces more than 1.1 percent UVB. Melissa Kaplan, author of Iguana for Dummies, recommends either the Durtest Vita-Lite or Zoo Med's Reptisun as good lights. Over time, the production of UVB diminishes, and UVB bulbs should be replaced every 9-12 months.
For those species that require a UVB producing light, another source of light is generally required, as either a source of bright white light and/or heat. When placing the various heating and lighting elements, they need to work together. Place the UV lights and the basking light on the same side of the enclosure, or the reptile might spend its time basking and be too far away from the UVB lamp to reap its benefits.
"Caring For Your Lizard". Pet Industry Joint Advisory Council, https://pijac.org/sites/default/files/pdfs/lizard_new.pdf.