Iguana Temperature and Housing
Cage Temperature and Basking Spots Iguanas spend much of their day in the tropics soaking up the sun and prefer it slightly warmer than most reptiles. Cage temperature should not drop below 75" F at night and gradually rise to between 85 and 95" F during the day with a localized warm spot or basking area of 97 to 99 F. Numerous studies of wild iguanas have shown that adult iguanas maintain a body temperature between 96.8 and 98.6" F by basking in the sun. Iguanas are hind gut ferments and it is probably not coincidental that mammalian hind gut ferments also have similar body temperatures. Assuring your iguana has a warm spot is important for proper digestion. Several sources recommend much hotter basking areas of 100 to 110" F but this seems dangerously hot. It is important that a thermal gradient exists within the cage so that the iguana can behaviorally thermo-regulate. It needs to be able toward up to a preferred body temperature but also move to a cooler area if getting too hot. The basking area can be provided by suspending over the cage a ceramic bulb or a 60 to 100 watt incandescent light bulb within a reflector. The bulb should radiate through a screen top so it warms a branch or flat rock to 99" F (this temperature should be verified using a glass bulb thermometer placed at the basking site for five to ten minutes). Make sure the iguana cannot come into direct contact with the bulb, reflector or the screen top. Iguanas have been known to hang directly on light bulbs while their skin slowly burns. The best way to heat the rest of the cage is with a space heater keeping the room between 75 and 90 F. Other less desirable heat sources include under-the-tank heating pads, heat tape or multiple ceramic bulbs at various distances from the enclosure to give a temperature gradient. Anything too hot to rest your hand on or under for several minutes will eventually burn the reptile. In general, heat sources outside the cage are much better.  Lighting Given that artificial sources or ultraviolet (UV) light rays may be only marginally effective it makes sense to purchase high quality bulbs, replace them annually and consider using a combination of two different kinds of bulbs. Black lights have no more UV radiance than other fluorescent lights but they produce only a dim purple visible light. Combining the black light with a full spectrum bulb probably produces a more balanced natural light. A two bulb fluorescent light fixture with a black light (General Electric Co.) and either a Vitalite (Durotest Corp.), a Repitesun* UVB310 (ZooMed), a Chroma-50 (General Electric), or a Colortone 50 (Westinghouse) less than 2 feet from the animal works well. The UV output of these lights decreases with age so replace them every year. Plant lights and poster black lights do not produce enough UV light in proper wavelength to be of much benefit. In warmer areas of the country where it is possible to take you iguana outside, sunlight is the best source of UV light and is recommended for at least fifteen minutes each day. Unfortunately glass and most plastics filter out UV light unless it is specifically UV light transmissible, so allowing your iguana to sun itself in the window does not provide it with the necessary UV light. Additionally your tank cover should be screen or UV light transmissible.
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