To survive, reptiles require not only heat but also adequate exposure to the full spectrum of light. Turtles, iguanas, uromastyx, and other "basking" reptiles need ultraviolet light - which is found in the middle section of the light spectrum - to survive. Reptile owners need to know about two types of UV light, A rays and B rays.

Ultraviolet B is essential to the health of reptiles. Exposure to UVB allows them to synthesize vitamin D, and reptiles (like humans) need vitamin D in order to absorb calcium from their diet and maintain strong bones. Without sufficient UVB exposure, many lizards suffer metabolic bone disease, and turtles end up with soft shells.

Ultraviolet A, scientists think, may comprise the rays that allow reptiles, who see in color, to identify their prey, their predators, and members of their own species. According to hobbyists, UVA also influences a reptile's appetite, reproductive behavior, and aggressive behavior.

Another consideration is that reptiles depend on the day-and-night light cycle, or photoperiod. Diurnal species (those active in the daytime) need to rest at night, in the dark, while nocturnal species need the shadow of darkness to hunt for prey.

Your objective is to simulate the natural light exposure - both type and duration - that your reptile's species gets in the wild. Fortunately, the growing interest in herp care has pushed manufacturers and suppliers to come up with reliable and specialized lighting products. Remember, glass filters out the beneficial light emitted from these bulbs so make sure you do not use a glass top between the light and your pet. Make sure you choose the lighting products that suit your reptile's needs. Here's a rundown on the possibilities:

• Incandescent Light. This is what's emitted from the standard light bulb most of us use at home. Incandescent light provides little of the UVB so beneficial to many reptiles, but it does give off a certain amount of UVA as well as heat. An incandescent bulb is an inexpensive and effective heat source for your reptile's terrarium.



• Fluorescent Light. This phosphor-coated tube is the right source for those essential UVB rays. However, a fluorescent lamp, known as cool light, will not serve as a heat source for your reptile's home. Moreover, not all fluorescent lamps are created equal - be sure to buy those specifically designed for reptile use and high in UVB emission. You'll need to replace these lights every six to 12 months because their emissions degrade with use. To give your reptile the full UVB benefit, install the bulbs no farther than 1.5 feet above your pet's basking spot.


• Full-Spectrum Lightbulbs. It's easy to assume that this would be the ideal solution to your pet's needs for different kinds of light. In fact, the term "full spectrum" relates only to visible light and some manufacturers take advantage of the lack of regulations on how the term is used. "Full-spectrum" sources attempt to imitate sunlight, but they do not necessarily emit UV rays and will not provide high UVB intensity. Nonetheless, there are good full-spectrum lights on the market that work well for simulating natural sunlight; they seem to have positive physical and psychological effects on reptiles. If possible, assure the well-being of your herp by using both a UVB-enhanced fluorescent bulb and a full-spectrum light.



• Black Light (or UVA). Some reptile caretakers opt to have separate UVA and UVB sources. Especially for nocturnal species, black light has become a popular source of the UVA wavelength that allows reptiles to see better in the dark. Nocturnal or otherwise, reptiles benefit from the intense UVA that commercial black lights provide. Be careful, though: Too much ultraviolet light will cause problems.



• UVB Bulb. Leading manufacturers of herp supplies have come up with bulbs that emit mainly UVB, specifying the emission as a percentage. As some reptiles habitually bask under the bright desert sun, your pet may benefit from strong UVB exposure, but this intensity could pose a risk to you. Products emitting more than 8 percent UVB are labeled "not for human use." Fearing adverse effects such as skin cancer and eye disorders, many reptile owners are opting for lights that give off only 3 to 5 percent UVB or less.



• Light Hood or Shroud. To make it easier to install and arrange your light and heat sources, check out the various models of hoods, shrouds, and strips. See that they're equipped with separate switches and outlets for your different fixtures.



• Timer. Several types will help you regulate the photoperiod for your reptile's enclosure. These include simple on-off timers and programmable digital timers, which you can preset for weeklong schedules.

Be sure to research the needs of your particular reptile, as no two species are exactly alike in this respect. Your efforts will have a bonus for you: Good lighting allows you to view all of the amazing colors that your herp naturally displays and will stimulate the fascinating behaviors of a healthy reptile.