January 1996: Green Iguanas in the Classroom

Iguanas are strong and fast. They seldom bite, but their jaws are powerful and can inflict a painful injury. If an iguana is not docile, do not handle it, particularly if it is an adult. As should be a common practice in handling any animal, after touching an iguana, always wash your hands. Instruct children not to kiss the iguana or put their fingers in their mouths before washing. Always carefully supervise any child handling an iguana.

Diet

Your iguana has a much better chance of surviving to a ripe old age (10 to 18 years!) if you have a proper understanding of its nutritional needs. Many people are surprised to learn that green iguanas are vegetarians, their digestive systems designed similarly to those of ruminants such as cows. Iguanas (and many other tropical and desert species of herbivorous lizards) are known as hindgut fermenters. Their cecum and colon contain symbiotic protozoans and bacteria that aid in the digestion of fiber, cellulose, and complex carbohydrates.

Be sure to feed your iguana often (once a day for hatchlings, every other day for adults), and provide it with a nutritionally balanced diet (see Iguana Feeding Tips). Iguanas require a body temperature of at least 88° F (31° C) to properly digest their food, so provide appropriate warmth.

While many iguanas relish crickets and other insects, animal protein should never form the mainstay of your animal's diet. Insects should be offered only as occasional treats. Health problems associated with the ingestion of too much animal protein may include liver degeneration, visceral gout, infertility, and calcium deposits in the internal organs. Do not assume that iguanas in captivity automatically eat what is best for them-they have been known to devour pizza, ice cream, and other "junk food" when given the opportunity!

Metabolic bone disease is one of the most common (and serious) dietary problems in iguanas and many other herbivorous reptiles. It is caused by a lack of usable calcium, and its symptoms include swollen jaws and limbs and fibrous connective tissue buildup to replace decalcified bone. Proper skeletal development of juveniles requires very large amounts of usable calcium. Iguanas of all ages need approximately two parts of calcium to one part of phosphorus in their diet for the calcium to be properly absorbed (or "usable").

For optimal health, green iguanas should be fed vegetables and fruits high in calcium, or their diet should be supplemented with powdered calcium. Regardless of the amount of calcium provided, green iguanas kept indoors also require vitamin D3 (for utilization of calcium). Many reptile calcium supplements also contain vitamin D3, which cannot be provided by plant matter. Be sure to follow the manufacturer's or your veterinarian's recommendations carefully, as vitamin or mineral overdoses may be life-threatening.

Housing

For hatchling iguanas, which are generally about 10 to 18 inches in length, a glass aquarium with a screen top provides an affordable and easily obtained first habitat (Fig. 3). While a 20- or 30-gallon tank is sufficient to house a young iguana, you may want to start with a larger enclosure (such as a 55- to 135-gallon terrarium). Iguanas grow very rapidly in their first 2 to 3 years of life, so the initial investment in the larger habitat will probably turn out to be more cost effective and practical than starting with the smaller tank.

Figure 3 Basic habitat for a hatchling iguana. A basket light resting on the screen top will complete the setup.

Iguanas approaching sexual maturity (2 1/2 to 3 feet in length) should be kept separated from others, as they may become territorial and aggressive. If you are just beginning to keep iguanas, you should purchase only one to start with.

Iguanas longer than 4 feet will require some sort of custom or specialty housing. It should provide vertical climbing space, with the habitat's dimensions as follows: length at least 11/2 times the animal's length, width 2/3 the animal's length, and height the same as the animal's length. For details on building or buying custom cages, consult a complete iguana care book or a reptile hobbyist magazine.

Appropriate materials for the bottom of the cage include newspaper (economical, easy cleaning), pine bark (attractive and holds moisture to provide air humidity), alfalfa pellets (somewhat absorbent, yet safe to ingest), and reptile carpeting (attractive, needs to be washed and dried for cleaning). Be sure to provide branches for climbing and basking. Daily misting with water is recommended, especially for younger animals. A shallow dish of water should be provided at all times and changed daily. Iguanas are clean animals that tend to defecate in one area of the cage (often in the water dish or in a tray with sand), so cage-cleaning may turn out to be a minimal part of iguana maintenance.

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