Reptiles – even captive-bred specimens – are wild animals who must live in a simulated version of their natural habitat. Different species require vastly different husbandry parameters, although the most important aspects to address for most species are the enclosure's size, temperature, lighting, humidity and furnishings. In most cases, reptiles do not require a habitat that visually resembles their natural habitat; most merely require a cage that functions like their natural habitat does.
Your pet reptile will spend the majority of his life inside his cage. Accordingly, it is important to provide a suitably large habitat to ensure your pet has enough room to get adequate exercise and to engage in typical behaviors. A cage that's too small can be detrimental to mental health.
Different species require different amounts of cage space. As a general rule, some of the most common small reptile pets – such as leopard geckos (Eublepharis macularius), bearded dragons (Pogona vitticeps), crested geckos (Rhacodactylus ciliatus), ball pythons (Python regius) and kingsnakes (Lampropeltis spp.) – require 2 to 10 square feet of cage space. Cages of these sizes are readily available commercially, but for larger species it may be necessary to construct your own cages. Some common pet species, such as green iguanas (Iguana iguana), water monitors (Varanus salvator) and Burmese pythons (Python bivittatus) require closet- or room-size cages.
Heating the Habitat
Most pet reptiles require habitats that are warmer than the temperatures at which most people keep their homes. A variety of commercial heating products exist – consider heat lamps, heating pads, heat tapes and radiant heat panels, which make it possible to manipulate the temperature of your pet's cage. Whatever heating device you decide to use, place it at one end of the cage. This allows you to establish a thermal gradient, giving the animal access to a variety of temperatures.
The warmest side of the cage – the basking spot – should be between about 85 and 125 degrees Fahrenheit, depending on the species you keep. Typically, forest- and mountain-dwelling species prefer lower temperatures than desert-dwelling reptiles do. In all cases, use a high-quality digital thermometer to monitor the cage temperatures.
Some reptiles do not require any supplemental lighting; the ambient light from the room is sufficient. This is true of most snakes and nocturnal lizards – especially those who naturally live under the permanent shade of a forest canopy. Conversely, turtles and diurnal lizards almost invariably require high-quality full-spectrum lights to remain healthy. These lights must not only produce bright visible light, they must also produce ultraviolet rays – specifically those in the UVA and UVB frequency ranges.
Keep the lights on a consistent schedule by plugging them into an automatic timer. If your pet hails from the tropics, keep the photoperiod consistent all year long. However, it is wise to adjust the light schedule for temperate species to reflect the changing seasons. For example, give your North American green anole (Anolis carolinensis) about 14 hours of light in the summer, 10 to 12 hours of light in the spring and fall, and 8 hours of light in the winter.
Different reptile species require different humidity levels to thrive. Most species that hail from forests require higher humidity than those evolved to live in drier climates. Increase cage humidity by incorporating a larger water bowl in the habitat, dampening the substrate or misting the cage with water. The best ways to lower cage humidity are to reduce the size of the water bowl or increase the amount of ventilation in the cage.
Furnishing the Habitat
Now that you have an enclosure with proper temperature, light levels and humidity, you must add substrate, a water dish and any furnishing necessary. The substrate's primary job is to absorb liquids and facilitate cage cleaning. In many cases, this means that you do not have to use the same kind of substrate your pet lives on in the wild. Instead, you can use paper towels, newspaper, hardwood mulch or shredded aspen. Burrowing animals require a particulate substrate, but surface-dwelling or arboreal animals often thrive on a newspaper substrate.
Additionally, almost all reptiles require hiding places. These can take the form of natural-looking items such as hollow logs and pieces of bark, or utilitarian items like plastic tubs and cardboard boxes. You can add decorative items, such as live or fake plants, photographic backgrounds or faux rock walls, but these are primarily beneficial to the keeper rather than the kept. Arboreal species require suitable climbing furniture. You can use real wooden branches if you sterilize them, or use artificial items such as PVC pipes or closet rods.