Green Iguana Care

Steven D. Garner, DVM, DABVP Diplomate,
American Board of Veterinary Practitioners,
Chief of Staff, Safari Veterinary Care Centers,
(e-mail) docgarner@safarivet.com

The Common Green Iguana is a native of the tropical jungles of Central and South America. is the most popular reptile kept in captivity in the United States. The typical Green Iguana is colored varying shades of green, from brilliant emerald to a more ashy gray-green. Coloration can vary depending on where an individual originated from geographically. The overall health and nutritional status of the iguana can also affect the coloration. Black bands ring the tail, and a row of tooth-like scales runs from the nape of the lizard’s neck and down its back. Adults may reach 40-60″ in length.
Physical Appearance: Nostrils used for breathing and for salt excretion. Iguanas sneeze out salt through their nostrils. Tongue is essentially used for smelling. You should notice your iguana stick its tongue out frequently, apparently tasting things as he walks along. This is mainly for identification purposes. Ear, or tympanum, is that clear, round object on each side of your iguana’s head. Under the ear is a very large, round scale called the subtympanic plate. This scale does not have any biological function. Under the jawbone is a large piece of hanging skin called the dewlap. The dewlap is extended when the iguana is feeling threatened and wants to make itself look big and scary. If your iguana extends its dewlap when you or another iguana goes near it, it may be interpreted as a sign of stress, or at least discomfort. If you walk closer and then gently stroke your iguana on its sides or head and the dewlap relaxes, then your iguana has probably recognized you and is once again at ease. Sometimes your iguana just might want to let you know that you are in its territory, and the dewlap will extend as you approach.
Natural Behavior: In the wild, the iguana will spend most of its time basking in the sun. The preferred site is usually the highest branch in the forest canopy and hours each day are spent exhibiting this behavior. Young iguana’s have three defense mechanisms. They will leap sporadically from treetop to treetop in hopes of evading their predator or they will drop quickly to the forest floor and run away. If the iguana’s tail is grabbed, the iguana will break off its tail and continue to run. All of these behaviors are potentially dangerous in a captive situation where the iguana may leap from a hand or drop to a hard floor and injure itself. When threatened an iguana will whip its tail, puff up its dewlap, stand straight on its front legs and swing its head from side to side. An iguana that is continually demonstrating this behavior is stressed and stressed iguanas do not do well in captivity. Iguanas are very territorial and once they are past juvenile stage, do not do well when housed together or with other reptiles. Nature sees iguanas in the hot and humid rain forests, high in the canopy, basking in the sunlight. What follows are recommendations to re-create nature’s scene in a captive environment.

Cage Environment: Hatchling and juveniles can start out in a 20-gallon “long” aquarium, but quickly outgrow these quarters. A full-grown adult needs a lot of room, and the minimum dimensions should be 6′ x 6′ x 4′. Iguanas are active lizards, and need a variety of climbing areas (thick, sturdy branches propped up work well) and basking rocks and ledges. A pool large enough for the lizard to soak (such as a dishpan) should be available. Live plants such as Pothos and spider plants add a nice touch, but the iguanas may snack on the leaves, therefore you should make sure they are non-toxic. For substrate, newspaper is easy to clean and inexpensive. If you desire a more attractive alternative, try cage carpeting (like Astroturf. If you have multiple pieces of carpet, you can simply replace the soiled carpet with the clean carpet. The soiled carpet can then be rinsed and cleaned with a bleach solution (One part bleach to ten parts water). You should always rinse items thoroughly that have been cleaned with bleach or any detergent. Another popular substrate is rabbit food. These pellets are not harmful to ingest, but you must be dedicated to scooping out soiled rabbit pellets if you choose to use them. Avoid using chipped bark, peat moss, sand, wood shavings, kitty litter, or dirt as cage substrate. These materials are difficult to clean and may harbor mites and harmful bacteria. Certain woods, cedar and pine, have aromatic oils that are irritating to the eyes, skin and respiratory tract of reptiles. These should never be used.

Temperature: 65-72F night time low, 82-95F daytime high. To achieve this range, use an under-tank heater to heat the entire cage to the low 80s. Add an incandescent spotlight over a rock or branch so the iguana can bask. Experiment with light bulbs of different wattage until the basking area reaches the mid-90s. The cage should have a temperature gradient, so the lizard can choose the temperature that is most comfortable at that time. For example, iguanas will bask under the light after eating a meal (this helps with digestion), and then move to a cooler spot later. DO NOT use hot rocks! Iguanas use radiant heat from above not heat from below. Hot rocks often burn them and these burns can be severe and fatal.
Lighting: Green Iguanas also need a full-spectrum fluorescent light to thrive in captivity. Without it, they cannot effectively process calcium and specifically vitamin D3. This can lead to metabolic bone disease (MBD. These special lights mimic sunlight, and are sold by a variety of manufacturers under different names (such as Duro-Lite and Vita-Lite). Artificial lights will do in a pinch, but nothing beats exposure to pure sunlight. When outdoor temperatures are above 80 F allow your Iguana to bask outside in a wire enclosure, or in a secure pen where he can enjoy the natural sunlight. Do not put the iguana in direct sun in a glass enclosure. The glass magnifies the heat causing cage temperatures to rapidly reach fatal levels. In addition, light coming in through window glass or Plexiglas will not work; the glass filters out beneficial rays in the wavelengths lizards need.
Photoperiod: The photoperiod is simply the length of time your iguana is exposed to light. The recommended photoperiod for iguanas is pretty simple: plug your heating lights and ultraviolet lights into a timer so that they turn on for about fourteen hours each day. During the time that the lights are off, heat will be supplied from the under cage heat source.

Diet: Iguanas are mainly herbivorous (plant eaters) They will eat leaves, flowers, and fruits of plants,
and 90% of the diet should consist of a salad made up of a combination of the following greens:
beet greens, broccoli leaves, cabbage outer green leaves, mustard greens, tofu, turnip greens, dandelion leaves, romaine lettuce (not iceberg), Chinese cabbage, kale, collards. You can mix in some fruits as a treat: bananas, figs, apples, strawberries, sweet potatoes, peas, and beans. The last 10% of the diet should consist of animal-based foods: pinkie mice, crickets, mealworms, and wax worms.
Soaked alfalfa pellets (rabbit chow) provides an excellent source of protein, calcium and fiber. The soaked pellets can be crumbled over the salad. Two to three times a week, sprinkle the “salad” with a calcium supplement. The supplement should contain calcium with Vitamin D3. Supplements with phosphorus should not be given. If this sounds like a lot of work, it is. If you cannot commit yourself to shopping and chopping just for a lizard, don’t despair! There are a variety of prepared iguana chows on the market, which are very nutritious. Even if you normally feed him salad, you can still sprinkle the chow over his food twice a week to make sure he’s getting a balanced diet.
Calcium and Phosphorus: The food that you give your iguana, on average, should contain about twice as much calcium as phosphorus. Oxalic Acid: Oxalic acid, a chemical found in many plants of the genus Oxalis, binds with calcium to form calcium oxalate, an insoluble salt. When your iguanas eat a diet primarily of foods high in oxalic acid such as spinach, rhubarb, beets, celery stalk or Swiss chard, the oxalic acid binds with the calcium in these vegetables, rendering it unusable. Goitrogenic Cabbages: Like oxalic acid-rich vegetables, many vegetables in the genus Brassica (the “cabbage-like” vegetables) should not be fed in excess. Cabbage, kale, bok-choi (Chinese cabbage,) broccoli, turnips, rutabaga, cauliflower, and Brussels sprouts can all cause thyroid problems in iguanas. In short, do not feed any of the eight aforementioned vegetables in excess. Not all members of the Brassica family are harmful. Collard greens and mustard greens are good for iguanas. Dog, Cat and Monkey Chow: Commercial dog, cat or monkey chows contain excessive levels of protein, minerals and vitamin D. When fed to herbivorous reptiles over time these animals will develop mineralization of soft tissues such as kidney, vessel walls and heart muscle. These changes are ultimately fatal. Iguana Commercial Diets: The manufacturers of commercial iguana diets claim that their products contain all of the nutrients essential to the survival of green iguanas however, extensive research into the actual nutritional requirements of iguana is lacking. These diets are convenient and can be fed in addition to a balanced salad diet as described below. Home Prepared Diet: A good basic diet for iguanas consists of collard greens, turnip greens, mustard greens, parsley, dandelion greens, green beans, figs (raw or dried), green peppers, escarole, raspberries, leeks, snow peas, blackberries, grapes, radish, okra, pears, pricklypears. These items should be chopped into bite size portions (a food processor works well), mixed well and served fresh daily to your iguana. Vitamin and Calcium Supplementation: Commercial reptile vitamin supplement which contains beta-carotene rather than vitamin A is preferred because vitamin A can cause problems in excess while beta-carotene is converted to vitamin A as needed. The calcium supplement should contain only calcium and vitamin D3. A supplement containing phosphorus should not be used. Such a supplement does little to counter balance the high levels of phosphorus present in most vegetables. Water: Vegetables are comprised of mostly water – above 90% in many cases. Iguanas obtain most of the water that they need from the food however, you should still provide a water source i.e. a shallow bowl or daily misting of the cage.

Multiple Iguanas: All iguanas have different personalities. Some will get along well and some will not. As juveniles, most iguanas tend to live in harmony however, as they mature; males tend to be the most aggressive and territorial. Groups of females tend to get along better than groups that contain one male. Females can be territorial as well and problems might arise.
Nail Trimming: Iguana toenails can be very sharp and may inflict severe scratches. It is a good idea to keep them trimmed. The only part of the nail that you should clip off is the pointed tip. If you look at your iguana’s nails, you will see that there is a quite defined pointed tip, which is attached to the larger part of the nail, which is attached to the toe itself. You do not want to cut the larger part of the nail, which contains the blood vessels. Have styptic powder available when trimming your iguana’s nails. If you cut too far and the nail starts to bleed, the styptic powder should be packed onto the nail to stop the bleeding.
Bathing: Water temperature should feel pretty neutral to the touch! Soaking for 15-30 minutes is recommended, often stimulating your iguana to defecate in the water. Soaking in lukewarm water is one of the procedures used to treat constipated iguanas. If your iguana does defecate in the water, you should drain the tub and start again with fresh water.
Excrement and Potty Training: Most iguanas defecate about once a day. There should be three parts to your iguana’s bowel movement. There should be a solid bowel movement, not unlike a mammal’s. There should be a very liquid part that may be of varying consistency from that of uncooked egg white to that of water. Finally, there should be a white section that turns chalk-like when it dries, which consists of urates. Your iguana’s excrement should contain all three parts, although the amount of each part may vary from day to day. Iguanas tend to defecate when they soak in warm water. On a daily basis, you can let your iguana soak in the warm tub until it defecates.
Growth: Your iguana will grow very rapidly until it is about two or three years old. Growth rates in iguanas vary, depending on the individual, and also on diet. After your iguana turns three or so, it will continue to grow but at a much decreased rate. Iguanas can grow to be six feet long (the tail is usually about twice to three times the length of the body) and weigh up to 15 pounds.
Sexing: Most iguana owners like to know if their iguanas are male or female. When very young, it is virtually impossible to tell the difference through physical appearance. As they get older, however, there are some visual cues that can help you distinguish between the two sexes. One of the biggest physical differences between males and females is the size of their femoral pores, which line the undersides of their rear thighs. Male pores are much larger than female pores, especially in older specimens. Other differences include body size. Females tend to be more heavy-bodied than males, but males generally grow larger, have broader jowls, and have more developed dorsal crests. Finally, males develop a bulge behind their cloacal vent as they mature. This bulge is, of course, their hemipenes. (Male iguanas have two penises, together called the hemipenes.) Females do not have such a bulge in that area. The sex of an iguana can be determined from a specific blood test in which the DNA reflects the sex of the lizard. The test is 100% accurate and can be done even in very young lizards. Your veterinarian can provide this service.

Breeding to Egg Incubation: If you have only one iguana that tends to get aggressive in the fall, you probably have a male on your hands that is interested in mating. Some males get especially aggressive at this time and turn on their owners! Some iguanas actually attempt to mate with their owners. Many male iguanas simply act a little territorial during mating season, and exhibit head bobbing and act a little more defensive than usual. This difficult behavior usually passes after a few weeks. Lone female iguanas do not tend to change their behavior during mating season. You will know if your female iguana develops eggs (gravid): her abdomen will become large and lumpy, and she will also go off feed for a few weeks prior to egg laying. If your female iguana does become gravid, you must supply her with extra calcium in her diet, and you must supply her with a place to lay her eggs. Female iguanas can develop eggs even when there are no males present. Preparing the Egging Box: Females dig burrows underground and excavate a small cavern in which they lay their eggs. They then back out and back fill the cavern and burrow. You need to recreate the digging area by making an egging box, a place for her to dig a burrow and lay her eggs in a cavern. Depending upon the size of the iguana, two huge kitty-litter pans, placed rim-to-rim and duct taped together, with an access hole cut in one end of the upper pan, will suffice (say 10-12″ snout-to-vent length). Larger iguanas will require a larger area such as garbage cans (made of plastic, with a lid) laid on its side. Duct tape the lid to the can, and cut an access hole at the highest point. Fill the egging box with the proper digging medium before taping it shut. What you need to achieve is soil, which you can easily push but which will stay in place when you take your hand away. Too hard, and the iguana can’t dig; too loose, and it falls back into the burrow or cavern. The following proportions to work quite well:

  • 14 parts potting soil (from peat, available from nurseries)
  • 1 part sand (from nurseries, or playground sand from hardware stores)
  • 9 cups of warm water

Mix thoroughly together, and test. If it falls back, add more water. If too damp, add more soil or sand.
The box needs to be placed in a quiet warm area. Place a heating pad under the egg-laying container or direct a basking light on it (making sure not to melt the plastic!). Introduce your iguana to the container. Hold her up to the opening, let her sniff/taste and look, and then put her down. When she is ready, and if
you have prepared the soil/sand mixture properly and the area is quiet and warm, she will go to work.
It can take 10 hours or so to lay all the eggs. The number of eggs varies from 12-40+. Iguanas that are calcium deficient may demonstrate signs of twitching, jerky gait or difficulty using her back legs. Immediate medical care is very important in these cases. Without proper calcium, these iguanas may become egg bound (unable to pass the eggs). This condition may require surgical removal of eggs and can be fatal.

When a symptom becomes visible to you, your iguana has probably been sick for a long time and hiding its illness from you. Contact your veterinarian. Many diseases can be completely reversed if caught in time and if a proper course of action is taken.

Shedding: Your iguana will shed its skin throughout its entire lifetime. Iguanas do not shed their skin in one large piece. Rather, it comes off in many small pieces. Warm water soaks aid removal of shed skin. Retained portions of skin are usually due to a lack of humidity. Retained skin around the toes, tail and dorsal spines shrinks as it dries and may cut off the blood supply resulting in loss of the affected body part. Retained skin must be removed by soaking and gentle peeling. Increasing the humidity in the iguana’s environment will help prevent these problems.
Color Changes: Male iguanas often develop an orange hue when in breeding season, this must be differentiated from the orange discoloration often seen with illness. Mite infestations may result in slightly raised patches of black discoloration on the abdomen and legs. Mites are microscopic and often hard to see. Newly imported iguanas often have raised black lesions that resemble scabs. These lesions are often caused by infection with fungus that results from overcrowding and stress during importation. Scars from wounds, burns and other trauma initially are white to pale pink, smooth and lack scales. With each shed, the area becomes smaller as new scales are produced. The new scales may be smaller, darker and arranged haphazardly when compared to the normal scales.
Tail Regeneration: Your iguana might lose part of its tail. In the wild, this serves as a defense mechanism against predators. Tails usually do grow back but they do not look like the original tail. In most cases it is a dull brown, has different-looking scales than the rest of the tail, and it never grows back quite as long as the original tail. If your iguana’s tail does break off, you may try to keep the area clean and dry. Application of a topical antibiotic ointment is recommended. It should grow back in time.
Sneezing: Your iguana may sneeze quite often. In most iguanas this is a normal behavior. Iguanas do not sweat as humans do, so they do not excrete salt through their skin. Instead, they do it by sneezing. If your iguana is in a glass enclosure, you may find white spots on the glass. Iguanas can also contract respiratory infections. Bubbles or liquid outside the nose and mouth can be indicative of a respiratory infection.
Burns: Thermal burns caused by hot rocks are commonly seen in iguanas. Iguanas can also burn themselves on lights that are used for heating. Lights should not be placed inside the cage; rather, they should be positioned outside the cage so they can shine into the cage.
Nose Abrasions: Nose wounds are common in many lizards that are housed in cages that have wire or screen on the sides. Iguanas may spend much of its time rubbing its nose against the sides, trying to escape. This behavior may be indicative of a cage that is too small.
Lumps/Bumps: The most common cause of a lump/bump is an abscess under the skin. Abscesses are swollen, pus filled areas of infection caused by bacteria. These lumps should be surgically opened and the hard, purulent material removed. Topical and injectable antibiotics are often needed. This is a job for your veterinarian. A lump on the tail may be abscess or cyst. Microscopic evaluation of the material in the lump is necessary to determine the difference.

Constipation: Most iguanas defecate every day or every other day. Others do so twice daily, and still others regularly skip two days. If it seems as though your iguana is not defecating as often as it should, then soak it for 20-30 minutes in lukewarm water. This action will sometimes stimulate iguanas to defecate. If this fails, you should contact your veterinarian. Other conditions such as parasites, intestinal torsion (twisted intestines), bloat, bladder stones and egg binding can be mistaken for constipation. If left untreated, these conditions can lead to severe infections and fatal complications.
Internal Parasites: Yearly fecal samples are recommended to evaluate for intestinal parasites. These parasites can cause generalized poor body condition, weight loss, diarrhea, intestinal obstruction and, in severe cases, death.
External Parasites: Mites are blood sucking parasites and are common causes of skin irritation, black spots on skin, ulceration and in severe cases anemia in infected iguanas. These mites can be black or red. Your iguana’s enclosure should be thoroughly cleaned and disinfected. You may use a bleach solution (one part bleach to ten parts water) for disinfection. You must rinse those areas thoroughly after cleaning. All branches, rocks, substrates, bowls and dishes must be soaked well in dilute bleach solution. Soaking your iguana in clean warm water will drown many of the mites. These mites feed on blood and heavy infestations can lead to fatal blood loss. In addition, these mites can spread bacterial infections. See handout on mites/ticks.
Food Refusal: There are many reasons why your iguana may refuse to eat. It could be a psychological problem, physiological problem, or both. Environmental causes include: low temperature, low humidity, excessive handling of shy species, overcrowding (may occur with only two iguanas in a cage), aggression from cagemates, lack of hide box for visual security, lack of UV light and lack of proper diet. Raising the temperature of the iguana’s enclosure to 85-90 degrees will help stimulate appetite and increase the function of digestive enzymes. Iguanas generally eat better in the summer months, then slow down considerably during the winter months. Gravid females eat less than normal as the eggs develop filling the abdominal cavity. Force-feeding is often necessary in these situations. Stress of movement to a new cage, placement of cage in a high traffic area or improper photoperiod may contribute to stress and hence decreased appetite. Internal parasites, external parasites, any kind of bacterial or fungal infection, as well as most other illnesses may cause your iguana to go off food. Iguanas with metabolic bone disease are often unable to eat due to their inability to grasp/chew food with their soft jaws. Anorexia (food refusal) is not a disease; it is a symptom of some other problem. You should consult your veterinarian to determine the problem and appropriate treatment.
Lethargy: Similar to anorexia, lethargy (decreased activity) is a symptom of a larger problem. It usually accompanies disease. Make appropriate adjustments in temperature, lighting and diet. If your iguana’s activity level does not improve, further evaluation by a veterinarian is recommended.
Paresis/Paralysis/Hind Leg Weakness: The most common cause is damage to the spinal cord secondary to collapse of one or more vertebrae secondary to metabolic bone disease. The onset is usually sudden and there may or may not be a history of trauma. Another cause of weakness in the rear legs without paralysis is deficiency of calcium and/or B vitamins. Frequently, these iguanas will have difficulty with urination and defecation.

Spinal Curvature: Scoliosis is curvature of the spine from side to side, often into a C or S shape. Kyphosis is curvature of the spine resulting in a hump along the back. Injury, calcium deficiency, malnutrition or birth defect can cause these deformities. Most of these defects are not reversible; however, in most cases the iguana can live a relatively normal life.
Metabolic Bone Disease: The most common nutritional disease among iguanas in captivity is metabolic bone disease (MBD) or fibrous osteodystrophy. When an iguana has MBD, it does not have enough calcium in the blood. This is most often due to a calcium poor diet. Other causes include Vitamin D3 deficiency, overload of phosphorous, and kidney disease. When the iguana’s blood cannot get enough calcium from the food it eats, it starts to take calcium from the bones. This results in the bones becoming fragile and soft. Signs of MBD include broken bones especially the long bones of the legs, a “crooked” back, lack of use of toes, twitching of muscles (tetany), generalized weakness, and failure to raise its body up off the ground when walking. In advanced cases, the legs and jaws develop a firm swelling giving them a “muscle-bound” appearance. This is due to the body’s attempt to strengthen the weak bones by surrounding them with fibrous tissue. The lower jaw may become soft and begin to contract backwards resulting in failure of the mouth to close completely. Very gentle squeezing of the jaw will cause the jaw to flex inward indicating severe calcium deficiency. Deformity of the jaw often results in exposure of the gingival tissue (gums) producing a dry, reddish-brown, scab-like material. The exposed tissue should be kept moist with petrolatum jelly and the discharge periodically removed. MBD is a reversible disease, especially when caught early and treated aggressively. If allowed to go untreated, symptoms progress to severe muscle weakness, muscle tremors, comma and eventually, death.
Breathing Difficulty/Oral Discharge: Increased respiratory rate and/or open mouth breathing may be a sign of over heating in otherwise healthy iguanas, especially those left unattended in the sun or a hot car. Other causes include blocked nostrils, pneumonia and foreign body blockage of the larynx. Iguanas excrete excess salts from glands located in the nostrils. This results in a clear discharge that dries to a fine white powder, which may be seen around the nares or on the sides of the cage. Infections of the sinus results in material from clear with bubbles to thick and mucoid. Foamy or thick discharge from the mouth is a sign of more severe disease and debilitation.
Salmonella: Salmonella is a bacteria that is present in the gut of about 90% of reptiles and may cause no clinical evidence of disease in the iguana, however, in people especially in the young and the elderly, it can be extremely dangerous, even deadly. It is important that you practice good hygiene when there are reptiles present in your household. After handling your iguana or items from your iguana’s cage, you should always wash your hands in a good antibacterial soap. Do not soak the iguana or wash cage/cage accessories in the tub or sink, do not place the iguana near your face or mouth and avoid handling the iguana if you have open sores on your hands. Young people; people on immunosupressive drugs; persons with AIDS, cancer, or diabetes; and the elderly are particularly prone to becoming sick from the bacteria, and it can be fatal. Testing of the iguana for Salmonella is possible but often gives unreliable results and is expensive. It is better to assume the infection is present and handle the iguana accordingly.