LIGHT, HEAT & UVB
What bulb do I use?
Which artificial light source is capable of providing visual light, UV light and infrared light (or heat)?
The only light source today that is capable of providing the three important aspects of light (UV, visual and infrared light) in a somewhat balanced way is a mercury vapor bulb. Unfortunately these bulbs are not suitable for the smaller terrariums because of their high wattage.
If heat is infrared light, how do I create heat gradients?
In heat you have conduction, convection and radiation. Heat gradients are automatically created when a light source is used as a heat source on top of the terrarium. The first energy to strike the ambient air and the objects therein is the radiation. The heated air will then result in convection whereas the heated objects will provide conduction of the heat. The nature of different matters (air, wood, glass, plants, sand, etc.) will result automatically in heat gradients. A well-decorated terrarium increases these heat gradients by preventing the radiation to reach the substrate or underlying dimensions.
It is said that nocturnal and carnivorous reptiles do not need Ultraviolet light, in which case is an incandescent light bulb sufficient?
Not necessarily. Incandescent bulbs are suitable light sources for nocturnal reptiles in some cases. However, we have to take into account that many nocturnal reptiles are exposed to direct or scattered sun light during the day. Some reptiles rest/sleep on tree trunks or outcrops during the day, some deliberately bask during daytime hours while feeding at night, and others start their activity before sunset. This means that some form of photosynthesis takes place with these species.
Also many carnivorous reptiles still need UV light for photosynthesis purposes, correct environment, food and signaling perception. Not all carnivorous prey is capable of supplying the necessary vitamin D3 levels. If the prey's liver is not consumed, vitamin D3 intake is inadequate.
We can thus state that many nocturnal and carnivorous still require balanced lighting systems and that several more factors, other than just day and night cycle or infrared exposure have to be taken into account.
What are the pros and cons of fluorescent lights?
Fluorescents are the most economical light source, both in energy consumption and price. They are capable of emitting high levels of UV combined with acceptable levels of visual light. The higher the amount of visual light the lower the UV emission and vice versa. A combination of two fluorescents (visual + UV) and a basking light (incandescent) is recommended since fluorescent lights fail to produce sufficient heat.
Compact fluorescents have the same spectrum characteristics and emission as linear fluorescents. Due to their compact size, and because they are self ballasted, they are often easier to install than linear bulbs that still require a ballast.
What are the pros and cons of Mercury vapor lights?
These bulbs have it all: UV, high visual light output and sufficient infrared radiation. However, the disadvantage is that they consume a lot of energy (100 watt and plus) in order to operate properly. The lower the wattage, the less stable the bulb is. They are thus only suitable for very big terrariums.
What are the pros and cons of Incandescent lights?
Incandescents are inexpensive but are not very energy efficient when it comes to visual light. They are excellent as an infrared source to increase the ambient air temperature or as basking light. This type of light source also fails to produce any UVB radiation.
What are the pros and cons of Metal halide?
Metal halides are one of the best possible light sources around, the drawback is that they are very expensive. They have a very high light output, are capable of producing sufficient UV levels, and have a high infrared radiation. The installation is very expensive since a ballast is needed plus a special fixture.
The new HCI (Osram) or CDM (Philips) fits any HQI (Metal halide) fixture but has a greater visual light production with the same energy consumption. The advantages are the same then as those of metal halide.
What are the pros and cons of Halogen lights?
Halogen lights are somewhat more energy efficient than regular incandescent lights since they produce more visual light.
How much Ultraviolet light do reptiles receive in nature?
Ultraviolet radiation is expressed in microwatt per square centimeter (mW/cm2) and varies tremendously from the poles (low) towards the equator (high). The amount of UVB radiation received on the equator on a clear day at noon is around 270 mW/cm2. However, this high amount of radiation decreases as the day passes, in the same way that it had increased since sunrise and taking into consideration that not all days are clear. In the wild, basking activities of most reptiles are limited to the early morning and later afternoon. The rest of the day is spent in the shade, in burrows, crevices or other shaded places, or at various places in leafy bushes, shrubs or trees. In tropical forests, home to many types of reptiles and amphibians, only a little direct sun penetrates the forest canopy and underlying layers to reach the ground.
Can we create these conditions in a terrarium?
Yes, absolutely, but…
Many commercial reptile lights today exceed this 270 mW/cm2 in an attempt to show the greatest UVB radiation. Some even exceed over 2000 mW/cm2, which is absolutely dangerous! Especially if you know that the 270 value of the sun is only measured at high noon on a clear day while most light bulbs are on between 10 and 12 hours with constant values. Reptiles accumulate these UVB rays during the day (10 to 12 hours), so there is absolutely no need to even emit 270 mW/cm2 continuously.
Conclusion: "More is not always better"!
What is the role of lighting in reptile keeping?
Light has several functions:
- Indicating night/day cycle
- Providing light to see properly
- Environment perception (visual & UV)
- Agonistic and signaling communication (visual & UV)
- Physiological well-being (UVA)
- Photosynthesis of pre-vitamin D3 (UVB)
- Coloration is light intensity dependent
- Thermo-regulation (infrared)
Is the importance of light often underestimated?
Yes, absolutely. Especially when it comes to intensity of both UV and visual light. Often though, the importance of high levels of UVB light is overestimated; "More is not always better". In lighting there are many aspects and it is important to offer a balanced lighting system. It has to cover the simple aspects from indicating day and night cycle to more complex issues like photosynthesis. Unfortunately consumers often only use incandescent lights, which in most cases are totally inadequate.
What is the relationship between reptiles and the sun?
The sun's energy ultimately drives all life processes on earth and reptiles are no exception. If we fail to provide the important life sustaining aspects of this energy in captive conditions we will fail to maintain thriving terrarium populations, not to mention reproduction.
With special thanks to Dr. Luc Lambrechts, Wilrijk (Belgium) for the veterinarian images.