Most reptiles that people have for pets are from the tropics and are kept indoors only. Thus, they lack natural light and humidity, especially in our dry environment. Husbandry — meaning the feeding, housing and activity — for captured reptiles is the cornerstone of successfully having a reptile as a pet. However, it is often overlooked and not researched for each particular species prior to purchase or adoption.
Ultraviolet light is a critical component to the captive reptile's environment. A wild reptile may spend many hours a day basking in the sun, absorbing UV light. These wavelengths of light are necessary for the body to manufacture the vitamin D it needs for proper calcium absorption from the intestines. Vitamin D is manufactured in the skin. Failure to provide UV light can predispose your pet to nutritional metabolic bone disease that is fatal if it is not recognized and treated.
A UV light source should emit light in the UV-B range (290-320 nanometers). UV-A light (320-400nm), although important in terms of behavior, does not aid in the manufacture of vitamin D. Most bulbs sold for use in reptiles provide both UV-A and UV-B. Examples of commercially available UV-B emitting lights are the Retisun, Power Sun by Zoo Med and Repti Glo lamp by Exo Terra. There are light bulbs with different spectrums of UV light that are available for different types of reptiles, according to their needs. The UV output decreases with age, so the bulbs should be replaced every six months or as directed by the manufacturer. For UV light to work, it must reach the pet in an unfiltered form, which means that you must make sure there is not glass or plastic between the pet and the light. Also, the light should be within 6 to 12 inches from the animal for the pet to receive any benefit. Although these bulbs are expensive, they are worth the extra cost, and often mean the difference between a healthy reptile and a sick or dying reptile.
Regular exposure to natural, direct outside sunlight is encouraged and recommended whenever possible. If you take your pet outdoors, make sure you provide a shaded area for the reptile to escape the sun if it chooses. Always supervise your pet while it is basking outdoors to prevent escape or attack from other animals roaming in the neighborhood. The amount of light your reptile receives each day, which is called the photoperiod, is very important. Photoperiod and temperature will generally decrease in the winter and increase in the summer. Failure to account for these changes in captivity results in problems in pet reptiles. Reproductive failure is the most common symptom and is especially problematic for females who may develop ovarian problems or chronic yolk resorption. Obesity can also develop with incorrect photoperiod as animals that are normally less active in the winter months will continue to eat at a summer pace.
Photoperiods have a greater seasonal variability the farther away from the equator a reptile's native environment is.
Electric timers can aid the regulation of photoperiod in captivity and mimic the reptile's natural photoperiod. Remember, your pet reptile cannot sense the change of seasons occurring outside your home. As a general guideline, allow for 14 to 15 hours of light in the summer and 10 tp 12 hours of light in the winter, depending on the zone of the animal's native environment. This is especially important in breeding situations. Proper lighting is a powerful "medicine" for proper reptile management. It is also known as an effective appetite stimulant.
Consult a veterinarian familiar with reptiles if you have any other questions or concerns regarding proper lighting.