HEATING, LIGHTING, AND HUMIDITY
To fare well in captivity, green water dragons require temperatures in the mid 80s Fahrenheit (F) during the day, dropping to 75–79° F at night. The easiest way to assure that your lizards achieve their desired body temperature is to provide basking sites, specifically raised areas near a heat source. This allows a green water dragon to regulate its temperature by moving to and away from a heated basking site. For this system to work, it is important that the heat source only covers a portion of the enclosure surface. The enclosure must have a cooler area the lizard can enter once it reaches its desired body temperature.
The simplest way to provide these conditions is to place a reflector-type fixture with an incandescent spotlight on the screen top of the enclosure so that it illuminates about 40 percent of the surface inside the tank. Depending on the size of the tank, a spotlight can be located either to one side of the enclosure (for small enclosures less than 48 inches long) or in the center (for enclosures at least 60 inches long). In large enclosures containing several animals, you can set up more than one basking site, again remembering that the spotlight should illuminate only about 40 percent of the surface area.
The basking site region should consist of a raised area, such as a large branch or cork log, with a width at least equal to that of the lizards maintained. The area closest to the bulb should measure 86–90° F. To achieve this range, you need to decide on the proper wattage and make adjustments with the help of a thermometer. The required wattage of the bulb will depend on the distance between the bulb and the basking site. As a general guideline, if tanks are kept at room temperature (low 70s F), a 100-watt incandescent bulb will be adequate for heating a standard 29-gallon (30-inch long) tank or a 30-gallon long (36-inch long) tank. With larger tanks (4 feet long and at least 2 feet high) it is usually necessary to use up to 150-watt spotlights. Always use a thermometer to assess the temperature in your setup. The heat generated from a basking light is the strongest directly under the bulb, but it will also spread from that point, raising the ambient temperature of the enclosure. Water in the substrate and the water container will also help disperse heat. In cool areas or when temperatures in a home drop into the low 60s F, a common occurrence during the winter months, raise the bulb wattage to maintain the desired temperature range. At night, when the spotlights are off, it may be necessary to provide additional heat using subtank reptile heating pads or lowwattage, infrared, ceramic reptile heat bulbs. Connect these heats sources to a thermostat to assure that night temperatures remain within the desired range (mid to high 70s F).
Small logs and branches make suitable perches for basking sites
Temperature and Light Controls
To keep your heat sources within the desired temperature range, you can connect them to various kinds of thermostats now available in the reptile trade. Most of these require a thermometer for adjustment. The more expensive thermostats, such as pulse-proportional thermostats, include sensors and can be set to the desired temperature. Whether you decide to use thermostatic controls or not, a thermometer is essential. It is the only reliable way to determine the high temperature under the basking site and the cooler temperature at the unheated end of your setup.
Timers are also very useful. If you connect your light sources into the timer unit, you can regulate the photoperiod (cycle of light and darkness) of your setup. It will also mean that you won’t have to worry about turning lights on in the morning or shutting them off at night.
Ultraviolet-B Lighting
Many reptile keepers, because of the health risks associated with giving a reptile too much or too little vitamin D3 in the diet, limit their use of supplements and, instead, provide a source of ultraviolet–B (UV-B) radiation to allow their lizards to synthesize their own vitamin D3. Although this process (scientifically, the photolysis of cutaneous provitamin D3 to previtamin D3 to vitamin D3) has not been specifically studied in water dragons, it is believed to be the primary source of vitamin D3 in diurnal insectivorous and herbivorous lizards that bask in sunlight. Vitamin D3 is essential for the absorption of calcium.
As should be obvious, the most readily available and least expensive source of UV-B radiation is sunlight. Exposing water dragons for four to eight hours a week to natural sunlight between 10 AM and 3 PM is considered adequate exposure for most lizards to synthesize enough vitamin D3 to meet their requirements.
The best outdoor basking cages for water dragons, basilisks, and sailfin lizards are made of a wood or plastic frame covered with nylon shade cloth. Shade cloth cages are the best choice because, unlike welded wire cages, they drastically reduce the risks of rostral abrasion and damage to the mouth. Both of these traumas commonly occur in wire cages as the lizards rub their snouts against the sides during escape attempts. In addition, the wall-like effect of a shade cloth tends to give these lizards a sense of security. Because there is always a risk of animals overheating when placed under full sun, always provide an area with shade (plants or other kinds of cover) when placing these cages outdoors. Days with outdoor temperatures in the mid 70s to low 80s F are perfect for outdoor basking.
Whatever you do, never put glass enclosures containing live animals in sunlight. The glass causes a greenhouse effect that can raise the temperature inside the container to a lethal level and kill your animals.
If you cannot provide natural sunlight, there are two sources of UV-B radiation made specifically for reptiles now available in the pet trade. These are reptile fluorescent UV-B bulbs and self-ballasted mercury vapor UV-B spotlights. If you use fluorescent reptile UV-B bulbs, place a fixture on top of the screen top with one or two bulbs running the length of the vivarium and over a basking site (raised to within 12 inches or less from the bulb). When using UV-B mercury vapor bulbs, which generate more UV-B than the reptile fluorescent bulbs currently on the market, it is important to limit their coverage to one end of a long tank so that animals may choose how much time they want to bask under them. In addition, do not use mercury vapor UV-B bulbs as an exclusive source of heat with water dragons. Our experiments with these bulbs clearly show that water dragons and basilisks choose to limit their exposure, and they require a separate incandescent heat source for thermoregulation. Some keepers limit exposure by simply connecting mercury vapor UV-B bulbs to timers so that they are on for only five hours a day.
If you decide to use a UV-B source, restrict D3 supplementation to no more than once every ten to fourteen days. If your water dragons are regularly (every week or two) fed whole vertebrate prey such as mice, vitamin D3 supplementation is not necessary. When raising insect-eating lizards, one of the most detrimental combinations is UV-B exposure with high levels of dietary D3 supplementation. This commonly leads to hypervitaminosis D (excessive levels of vitamin D), which, when combined with other factors (such as the amount of dietary calcium), can result in death.
The most common cause of enclosure-related fires is the misuse of heating equipment. To prevent the risks of fire, always use spotlight fixtures rated for the wattage bulb you are using. Most high-wattage rated fixtures have ceramic bases. Never place light fixtures near flammable materials, such as curtains, sheets, or tablecloths. If you have children or other pets, secure the fixtures to the screen so that they cannot be knocked off. If you have your lights set on a timer, always unplug them before moving them. Some fires start because an owner does maintenance work in the evening and leaves the light on top of a table or rug to access the inside, then retires before putting the light back on the tank. The next morning, the timer activates the light and it burns or ignites the furniture or rug. If using sub-tank heating units, read instructions carefully to prevent the risk of fire. Finally, always place a fire alarm in any room where you have reptile heating equipment.
Relative Humidity
Green water dragons enjoy 70–80 percent relative humidity. Generally, if you provide a large water container in an enclosure heated by spotlights, the evaporating water will raise the humidity to adequate levels. Adding plants to the setup and using a moistened substrate also helps raise humidity. In very dry areas, partially cover the screen top to raise humidity in the enclosure. Some keepers suggest a daily misting of the vivarium. Misting is fine as long as it does not result in soggy conditions that saturate the substrate or keep the water dragon’s skin perpetually moist. These conditions can result in bacterial or fungal infections of the digits and skin. If you decide to mist the enclosure, always do it early in the day when the heat sources are on. The heat speeds up evaporation and helps prevent the buildup of soggy conditions. Never keep water dragons in a mostly sealed enclosure with poor ventilation. This will raise the humidity to almost 100 percent and will almost certainly result in bacterial or fungal infections.