Green Iguana Care

Thomas H. Boyer, D.V.M.

10148 W. Chatfield Ave.

Deer Creek Animal Hospital

Littleton, CO 80127

Green iguanas (Iguana iguana) are popular pets and are the most common lizard in my practice. Owners receive a wide variety of conflicting information, often erroneous, on how to care for their iguana. Therefore the veterinarian must be a knowledgeable source of information because good medicine can only be built upon sound husbandry. Owners form initial impressions of their veterinarian based on how well the veterinarian can tell them how to care for their reptile. Thus husbandry is paramount to the reptilian veterinarian. Here are suggestions on husbandry.

Iguana iguana is a large diurnal arboreal folivore found from Mexico into Brazil. Both sexes lead solitary lives (12) except during the breeding season and are territorial (a fact that is largely ignored in captivity). In the past it was assumed that younger animals were partially insectivorous to facilitate rapid growth but now it is believed iguanas are generally herbivorous throughout their life (1,2) although they will eat carrion (3) and insects (4). Growing iguanas achieve faster growth rates by selecting diets higher in digestible protein and maintaining higher body temperatures which is believed to increase digestive efficiency (2). Studies in Panama (1) found iguanas ate leaves, fruit and flowers of select trees, vines and bushes in short frequent feeding bursts concentrated from late morning to early afternoon. Most forage species were abundant but effort was evident to eat less common species and seasonally available foods. Although a wide variety of species were eaten stomach contents typically consisted of one or two species and researchers speculate that dietary diversity is accomplished over a period of days rather than daily (1).

Adult iguanas are easy to sex because of the ventral femoral pores are much larger in males compared to females and males have hemipenal bulges at the ventral base of the tail. Males also grow much larger. In juveniles these differences are more subtle. Probing has been suggested as a method of sexing (12) but I haven't found this reliable. Sexual maturity can be reached within two years but breeding usually doesn't occur until the third year in captivity (8). Females in Panama lay clutches of 23 to 60 eggs (mean = 40) from late January to mid March during the dry season and hatchlings appear in 90 days at the start of the rainy season (6). Under artificial incubation at 27 to 35 C (80.6 to 95 F) eggs hatch in approximately 93 days. Larger females lay larger clutches (6).

Females need to excavate nests before they will lay. It is tempting to speculate this is one reason females often become egg bound in captivity. Artificial nesting chambers have been constructed from 6 half width solid cinder blocks (40 cm x 20 cm x 10 cm) and females avidly accepted them (6A). These were constructed in a pit by placing one cinder block flat at the bottom, one at each side, one across the back and two perpendicular to the others to form a roof. The cavity inside the cinder blocks was packed with 7 cm soil and two 15 cm inside diameter clay tubes 30 cm long were placed in line with the one open side. The whole structure was then buried including most of the inside of the tubes with soil tapering away to the exposed entrance. With a little imagination one could fabricate a similar, simpler structure in captivity.

In captivity iguanas grow rapidly (30 to 60 cm/year) reaching adult size in 2 to 3 years and can live ten to fifteen years if properly fed and cared for (7,8,12). Owners should invest in a larger aquarium initially or be prepared to purchase a large one later. A 20 gallon aquarium would be good to start but within a few years most owners must build large glass, plywood and screen cages. Wood should be sealed with non-toxic sealant such as polyurethane (8). Allow as much vertical space as is practical to accommodate their arboreal lifestyle.

Iguanas live solitary lives in the wild except for breeding and ideally should be housed individually in captivity (12). Unfortunately this is generally impractical and it is not uncommon for iguanas that have lived together for some time to suddenly tear into one another. For multiple iguana households several smaller cages are preferable to one large communal cage.

It is not advisable to give ones iguana free roam of the house because of the numerous hazards they can encounter (7). Other pets, particularly cats, regard iguanas as prey that must be attacked without hesitation.

The bottom of the cage should be lined with newspaper (the cheapest and easiest to use), astroturf (make sure it has no loose ends that can be eaten), wood chips (large enough that they can't be eaten), or alfalfa pellets. Avoid sand, gravel, dirt, crushed corn cob or kitty litter as substances because they can cause numerous problems and are difficult to clean (7,12). If one uses astroturf buy a second so a clean dry one can replace the one that is being washed and dried (7). If using newspaper or astroturf, cages should be cleaned weekly (or sooner if dirty). Alfalfa pellets and wood chips should be changed every several months but feces need to be scooped out several times per week. Constantly moist or filthy environments are potential sources of infection. For most cleanings hot water is enough to rinse out the cage, more thorough cleaning with a 3% bleach solution is only needed once or twice a year.

Hardwood driftwood branches for climbing and basking are appreciated. A water bowl big enough for the iguana to get in and soak is also needed, clean it whenever dirty or at least twice a week. Iguanas need access to water at all times (12) and not just once a week as has been suggested (8). In the native state >iguanas are usually found in close association with water. In drier parts of the country keep the cages humid, but not wet, by spraying it several times per week or use a humidifier.

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 75ø F at night and gradually rise to between 85ø and 95ø F during the day with a localized hot spot or basking area of 95ø to 100ø F (8). Numerous studies of wild iguanas have shown that adult iguanas maintain body temperatures between 36ø and 37ø C (96.8ø to 98.6ø F) by basking in the sun. Iguanas are hind gut fermenters and it is probably not coincidental that mammalian hind gut fermenters also have similar body temperatures (2). Assuring ones iguana a hot spot is important for proper digestion. Several sources recommend much hotter basking areas of 100ø to 110ø F (7,12) and this seems dangerously hot. It is important that a thermal gradient exists within the cage so that the iguana can behaviorally thermoregulate. It needs to be able to warm up to a preferred body temperature but also move to a cooler area if getting too hot.

Here are some suggestions on maintaining this temperature. Keep in mind that each setup is different so it is difficult to advise what will work well in each owner's home. The only way to know what temperature a cage is, is to use a thermometer (minimum- maximum thermometers are the best). After many years of checking temperatures one finds guess work to be unreliable and dangerous so insist owners purchase a thermometer. Remember reptiles are ectotherms so temperatures too low slow metabolism and predispose to illness whereas temperatures too high can rapidly kill reptiles.

The basking area can be provided placing a 60 to 100 watt incandescent light bulb with reflector outside the cage or resting on the screen top so that it warms a branch or rock in the cage. A small infrared light also works well but make sure it is at least 18 inches from the iguana. With either light make sure the iguana can't come into direct contact or get too close to the light of serious thermal burns may result. 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 75ø and 90ø F. Other less desirable heat sources include heat tape, heating pads or hot rocks. Again make sure any heating sources hot enough to burn ones iguana are not present inside the cage (anything too hot to rest ones hand on or under for several minutes will eventually burn the reptile). In general, heating sources outside the cage are much better.

An area of considerable debate and uncertainty within the herpetocultural world is the need for ultraviolet (UV) lights. UV lights are thought to be essential in basking species for photochemical production of the active form of vitamin D which in reptiles is believed to be cholecalciferol or vitamin D-3 which in turn assists in calcium uptake from the gut. Ultraviolet irradiation in the 290 to 320 nanometer wavelength catalyzes production of cholecalciferol in mammals and it is reasonable to assume this is true for iguanas as well. An alternative to UV lights is to provide preformed D-3 in the diet. Unfortunately vitamin D requirements are unknown for all reptiles and it is extremely toxic in excess amounts. Empirically 100 to 200 IU D- 3/kg/week has been used without apparent harm. It is easy to exceed this amount with minuscule amounts of most multi-vitamins and one finds many overzealous owners unwittingly ready to do this. Most adult iguana necropsies to have considerable evidence of hypervitaminosis D. Therefore until further information becomes available owners are recommended to use UV lights and moderate multivitamin supplementation.

Given that UV lights may only be marginally effective it behooves one to suggest the best combination. Black lights have more UV irradiance than other florescent lights (7,13) but produce dim purple visible light. Combining black light bulbs with other white light florescent bulbs produces a more balanced natural light (7). A two bulb florescent light fixture with a black light (General Electric Co, Nela Park, Cleveland, OH) and either a Vitalite (Durotest Corp., Lyndhurst, NJ). Chroma-50 (General Electric), or Colortone 50 (Westinghouse, North American Phillips Lighting Corp., Somerset, NJ) less than two feet from the animal works well. The UV output of these lights decreases with age so replace them every two years or sooner. Plant lights and poster black lights (BLB lights) fail to provide enough UV light in the 290 to 320 nanometers wavelength to be of much benefit in cholecalciferol activation (7,13).

In warmer parts of the country sunlight is the best source of UV light and is recommended. Unfortunately glass and most plastics filter out UV light (unless specifically UV transmittable) so windows don't help as a source of UV light for indoor animals. Likewise no glass or plastic should be between the light and iguana, screening is fine. There is unfounded fear (7,12) that florescent UV lights can cause damage to the skin. or retina (they don't) and some suggest filters to block UV light in 290 to 320 nm wavelength (14). This is the extrapolated wavelength believed important for cholecalciferol synthesis and use of these filters would defeat the primary purpose of the lights. The lights should be on for 12 to 14 hours per day year round and turned off at night. A timer helps keep them on a regular photoperiod.

Diets for green iguanas are an area owners have tremendous difficulty with and the following is a compilation of recommendations from several sources (9,10,11). For young growing animals eighty percent of their diet should be plant based and 20 per cent protein based. Once the iguana reaches adult size (this should take two to three years) the protein can gradually be reduced and the plant material increased to decrease the load on the kidneys.

Of the plant material 80 to 90% should be vegetables and 10 to 20% fruits. Most iguanas relish fruits but they are mineral poor so they should be restricted. Think of fruit as more of a treat that can be given from time to time. Those foods listed in bold print have a positive calcium to phosphorus ratio. Vegetables will make up the bulk of the diet and leafy greens with a dark green color will make up the majority of the vegetables. Dark leafy greens that are rich in calcium include collard, mustard, and turnip tops or greens, alfalfa or Timothy hay, alfalfa chow, Buffalo grass, and dandelions (flowers, stems and leaves), and should be the cornerstone of a healthy diet. Other dark leafy greens include bok choy, Swiss chard, clover, kale, beet greens, escarole, parsley, spinach, watercress, savoy, kohlrabi, and romaine lettuce. Other types of vegetables include alfalfa or radish sprouts (as well as other sprouts), asparagus, bell peppers, carrots, cucumbers, green beans, jicama, mushrooms, okra, peas, and pea pods, prickly pear cactus pads (remove the spines), shredded squashes (such as green or yellow zucchini), sweet potatoes, soybeans, and uncooked thawed frozen mixed vegetables (corn, green beans, lima beans, peas, carrots). Spinach and beets have calcium binders in them so they should be fed in moderation. Cabbage, broccoli, brussels sprouts, bok choy, cauliflower, kale, and other members of the cabbage family can cause thyroid problems if fed excessively but are fine in moderation (9). Flowers such as roses, nasturtiums, carnations and hibiscus are excellent. Mulberry leaves are good if available. The other 10 to 20% of the plant portion can be various fruits. Figs are one of the few fruits rich in calcium. Apples, apricots, dates, grapes, kiwis, melons, peaches, papayas, pears, plums, prunes, raisins, strawberries and raspberries are all fine in small amounts. Iguanas are fond of bananas unfortunately they have very little calcium present. Iceberg lettuce has little nutritional value.

The other 20% of the diet consisting of protein sources is also important. Canned, semi-moist, or dry dog chow, Purina trout chow, monkey chow, or Hikari chichlid pelleted fish chow, pelleted bird chows, or whole gold fish, baby mice or adult mice (depending on the iguanas size), drained whole sardines, soaked dry legumes (beans), tofu, hard boiled eggs, insects, earthworms, and commercial reptile diets are all important in small amounts. All the dry chows need to be first soaked in water until soft. Feed a wide variety of these foods not just a few. Dog food and monkey chow should be limited to less than 5% of the total diet because of high vitamin D content (9). Avoid cat food because it is too high in protein, fat and vitamin D for iguanas (10).

To make a salad wash, chop and mix three or more types of dark leafy greens, thawed frozen mixed vegetables, several types of fresh vegetables, a fruit and a protein source. Salads can be stored for a week in the refrigerator. For hatchlings it is important to chop food into very small pieces. Each week slightly vary the diet by offering different food. Finicky eaters can be encouraged to eat more by mixing preferred foods in heavily at first and then gradually decreasing them over a few weeks (7). Persistence eventually pays off with novel items but keep in mind iguanas also can have individual likes and dislikes.

How much to feed is a tricky question. In the wild, iguanas probably feed every day. In general feed enough that the reptile continues to gain weight and grow but not so much that it becomes obese. If the iguana eats all one offers and still seems hungry then feed it more. Most young iguanas grow very rapidly so one should notice appreciable growth on a monthly basis. Feed hatchlings daily until they are roughly six months old then they can be fed like adults, three times per week or every other day.

Every feeding sprinkle a light dusting of calcium carbonate, lactate, or gluconate on the salad. Iguana diets tend to contain excess phosphorus (9) so calcium supplements with phosphorus are not recommended. Do not oversupplement with calcium! A fine barely perceptible dusting is all that is required. My brother once told me he only supplements an amount of calcium that he expects equals the amount of bone growth for that dy. Obviously the correlation doesn't exist but it is a very handy rule of thumb for owners. Ideally with a balanced diet little calcium supplementation is necessary. If the iguana eats the variety if chows in the protein portion it is getting plenty of multivitamins. Multivitamin supplementation is only required if the iguana isn't eating any of the chows in which case a very light dusting of a good quality reptile or bird multivitamin once or twice a month is necessary. Multivitamin supplementation has been recommended with each meal (12), this seems excessive.

Variety is key to a healthy diet! Avoid feeding just dog food and a few vegetables and fruit. Until more is known it is prudent not to rely on any one item for the majority of the diet (particularly items known to contain large amounts of vitamin D such as monkey chow biscuits). Recheck patients a month or two after restricting their diet and go over diet again. Question owners as to what they are offering and what is being eaten (often there is tremendous difference that many owners are reluctant to reveal). Captive reptile diets are just beginning to be understood so keep an open mind as recommendations are likely to change in the future.

Wild caught iguanas are often shy and should be minimally disturbed until they are eating well and seem less nervous. Have owners resist the temptation to try and tame them immediately because this will further stress them and can be too much for an animal that is already maximally stressed. Allow them a few months to adjust to captivity. A hide box will give them a secure area in the cage for retreat. Particularly nervous individuals may need their cage covered so they don't pace at glass barriers or brush their snouts whenever there is movement outside the cage.

As one can see iguana husbandry is somewhat complex. Veterinarians must assume the forefront in promoting good husbandry and the only way to do this is to be cognizant of just what good husbandry is. Both your client and patient will benefit from your suggestions.

References

1) Rand, A.S., et al. The diet of a generalized folivore: Iguana iguana in Panama. J of Herpetology, 24(2)211-214, 1990.

2) Troyer, K. Diet selection and digestion in Iguana iguana: the importance of age and nutrient requirements. Oecology, 61:201- 207, 1984.

3) Loftin, H. and E. Tyson. Iguanas as carrion eaters. Copeia 4:515, 1965.

4) Hirth, H.E. Some aspects of the natural history Iguana iguana on a tropical strand. Ecology 44(3):613-615, 1963.

5) Troyer, K. Small differences in daytime body temperature affect digestion of natural food in herbivorous lizard (Iguana iguana). Comp Biochem Physiol, 87A (3):623-626, 1987.

6) Miller, T. Artificial incubation of eggs of the green iguana (Iguana iguana). Zoo Bio. 6:225-236, 1987. 6A) Werner, D.I. and T.J. Miller. Artificial nest for female green iguanas. Herp Review, 15(2):57-58, 1984.

7) Beltz, E. Care in captivity: husbandry techniques for amphibians and reptiles. Chicago Herp. Society, pp 42-43, 1989.

8) de Vosjoli, P. General care and maintenance of the green iguana. Lakeside, CA. Advanced Vivarium Systems, pp 1-32, 1990.

9) Frye, F.L. Biomedical and surgical aspects of captive reptile husbandry. Edwardsville, KS. Vet Med Pub Co, 1981, pp 19,24-25, 34-40.

10) Barton, S.L. Reptile nutrition: herbivorous species. Chicago Herp Society, 1984.

11) Boyer, D.M. An overview of captive reptile diets. Proc of the Student Amer Vet Med Ass Symposium, Ft. Collins, CO, 1987.

12) Anderson, N.L. Husbandry and clinical evaluation of Iguana iguana, Comp on Cont Ed for the Pract Vet. 13(8):1265, 1991.

13) Gehrmann, W.H. Ultraviolet irradiances of various lamps used in animal husbandry. Zoo Biology, 6:117-127, 1987.

14) Mader, D.R. Metabolic bone disease in captive reptiles. Vivarium, 2(4):12-13, 1990.

This is the HTMLized version of the text-only version of this document from The Iguana Den. Special Thanks to Kevin Egan for allowing this HTMLization of this document!