Green Iguana

Care of Green Iguana

 The green Iguana (Iguana iguana) is one of the most frequently purchased reptiles and one of the most frequent reptiles to visit the  veterinary office.  Often, the pet owner is not given proper information as to the needs of iguanas at the time of acquired.  It may be weeks to months before the devastating effects of improper diet, internal parasites or incorrect housing conditions take their toll, and the pet becomes ill.  This handout is a brief overview of care, but we recommend that you purchase a copy of The General Care and Maintenance of the Green Iguana by Philippe de Vosjoli for more detailed care.

Iguanas are diurnal, arboreal, tropical lizards of Central and South America.  They have been introduced into south Florida, and are currently predominantly bred in captivity.  In the wild, iguanas are virtually herbivorous, eating fibrous jungle leaves, flowers, and fruits.  They rely on fermentation of complex carbohydrates in their colon to produce 30-40% of the energy available from their diet.  The required bacteria are acquired in hatchlings by eating the feces of adult iguanas.  Iguanas facilitate this fermentation process and regulate their body temperature by basking in the sun, seeking temperatures above 85 degrees F (30 degrees C).  Their social rank is reflected in the prominence of their basking sites.  Adult animals may reach a length of 6 feet and weigh as much as 15 pounds, a fact that should be considered when purchasing that cute little green lizard in the pet store!  Adult animals require a large amount of cage space and may be quite dangerous to handle.  Their razor sharp teeth can inflict serious injuries and the tail when lashed can also cause skin lacerations or eye injuries (not to mention the pain that can be inflicted by their sharp claws).


Providing the proper temperature, humidity, and light requirements for an iguana is critical for the animal to survive in captivity.  Iguanas should be housed in large glass, plexiglas, or wooden cages.  A 20-gallon or larger aquarium is a good size to start with, as these reptiles grow at a very rapid rate in their first several months of life.  The cage should be lined with newspaper, artificial grass (astro-turf), or indoor-outdoor carpeting, with ease of cleaning being the most important consideration.  My preferred substrate is newspaper, because it is cheap and easiest to clean (just throw it away).  Do not use gravel, sand, soil, or kitty litter because the iguana may eat pieces of these materials and then develop a potentially fatal intestinal impaction.  These materials are also difficult on the animal’s skin, if they become dirty or are continually damp.  In general, stay away from organic beddings like mulch, walnut shells, coconut, corncob, etc as they are hard to disinfect and can harbor infectious organisms.

A water bowl should be provided with fresh water and changed daily for the animal to drink out of and soak in.  The bathtub and sink is also a good place for a daily swim for your pet.  It is better not to use a sink in which food is prepared, due to the risk of Salmonella contamination (if your pet is harboring this bacterial agent).   Ask your vet about the potential for Salmonella infection in these animals.  Many pets will defecate only when in water, which may make it easier for cleanup.

Humidity in the tank can be provided by lightly misting the area several times a day, adding an air stone driven by an aquarium pump into the water bowl, or with the use of a humidity box.  (See attached sheet on the construction of a humidity box).

A hiding area is critical for the animal’s mental well being.  The humidity box may be used for this, or any cardboard, wood or plastic container that is of sufficient size for the pet to enter and turn around in will suffice.


Iguanas are tropical lizards and should have supplemental heat added to their environment.  We do not approve of “hot rocks” being used for this purpose.  We frequently see serious thermal burns on the underside of baby iguanas caused by the uneven heating of the hot rock that in some instances has lead to death.  There should be a temperature gradient in the cage; meaning one should not attempt to make the environment the same temperature.  Under cage heating can be provided by a heating pad left on twenty-four hours a day and put UNDER the tank so that the animal does not have direct contact with it.  There are several types of specially made reptile heaters of varying sizes, some with thermostatic controls.  In addition, the pet needs a “hot basking spot” provided in the cage by an overhead heat and light source (a ceramic bulb works well).  The temperature in this area needs to reach 90 to 100 degrees F.  This light should be left on only 10-14 hours per day and should be turned off at night.  Putting the light on a timer is helpful.  Nighttime temperatures may drop to 70-75 degrees F.  Allowing your pet to live at “room temperature” all the time with no chance for thermoregulation will lead to serious health problems over time (it may take several years).  An inexpensive digital thermometer with a probe can be purchased at Radio Shack, and can be used to measure many points in the terrarium to ensure a proper heat gradient.

There is ongoing controversy about the usefulness of UV light in the captive iguana’s environment.  We know that certain types of UV light are important in helping Vitamin D production in the animal’s skin, which in turn is essential in facilitating the absorption of calcium into the body.  The question is whether the various light sources that claim to be most like sunlight are really doing the job.  The answer is that there is no substitute for natural sunlight, (none of the light bulbs currently on the market can absolutely reproduce sunlight).  However, since we live in a climate that prevents us from keeping our pets out doors all year (and glass windows block UV light rays out) we recommend using bulbs that provide at least some source of UV rays.  Vitalite and Chromalux bulbs are two that we recommend currently and should be placed so that the pet is no more than two feet away from the light source.  The advantage of Chromalux is that it is also a heat-producing bulb.  Consult with your veterinarian on proper light sources, because some bulbs can be harmful to the pet’s eyes.  UV bulbs need to be replaced every 6 months, because after that they no longer provide a useful spectrum.

We highly recommend during the warm summer months when the temperature is 80 degrees or higher, that you expose your pet to natural sunlight.  We recommend building an outdoor playpen with a shaded area where your pet can spend time on nice days.  Even putting your iguana on a harness and leash and “sunbathing” together with your pet can produce tremendous benefit.


This is the single most difficult area to manage in the pet iguana.  The most common disease problem that we see in pet iguanas is calcium and or vitamin D deficiency, which leads to stunted growth, softened and broken bones, muscle tremors, seizures, and death.  Juvenile iguanas have different dietary requirements than adult iguanas, a subject of which is still open to much discussion.  There are now various pelleted, ground, and frozen iguana diets available on the market, many claiming to be “complete”.  It is dangerous to use any of these foods as the total diet because dietary deficiencies are still seen despite the companies glowing claims.  If prepackaged diets are used, they should comprise no more than 75% of the total diet with the remaining 25% fed in the form of plant material (see examples of plant material below).  Vitamin and mineral supplementation may be eliminated altogether because the prepackaged diets already contain these materials.

If you are making up a diet of your own, you may want to follow these guidelines.  (Again, we urge you to consult The General Care and Maintenance of the Green Iguana by Philippe de Vosjoli for additional suggestions).

Juvenile “baby” iguanas (less than a foot in length from nose to vent – exclude the tail) can be fed a diet of 20% plant protein foods along with a variety of leafy vegetables, non-leafy vegetables, and a small amount of fruits.  They should be fed daily.

Medium “adolescent” iguanas (less than a foot in length from nose to vent – exclude the tail) can be fed about 15% protein and the rest as in the juvenile.  These should still be fed daily.

Large adult iguanas (1 – 1 ½ feet in length from nose to vent – exclude the tail or any time growth has stopped) can be fed 10% protein in the diet.  Some adult pets may only eat 2 to 3 times a week.  Concentrate on the leafy veggies and limit high phosphorous foods (those with an asterisk on the calcium chart included in this handout).

All food should be chopped up in small pieces, mixed well, and fed only in amounts that will be eaten within a few hours.  This will ensure that ALL foods are eaten and ALL the supplements are taken in.

Examples of plant protein foods:  Tofu, rabbit, guinea pig, or alfalfa pellets (put into a blender dry, ground into a powder and sprinkled over the food), wheat grass and alfalfa sprouts.  WE NO LONGER RECOMMEND USING ANIMAL PROTEIN SUCH AS DOG FOOD OR TROUT CHOW IN THE GREEN IGUANA DIET.  Although the use of animal protein has caused rapid growth as a youngster, it is now one of the factors suspected of causing kidney disease as the animal ages.

Examples of plant material: Use at least 75% of the plant material as dark green leafy vegetablessuch as mustard greens, dandelion greens, kale, Swiss chard, endive, romaine lettuce, carrot tops, turnip, and beet greens.  This is to satisfy not only the fiber requirements but also the calcium requirements.  One should use a minimum of three different greens daily.  The excessive use of only one or two items may lead to nutritional disease.  The rest of the plant material can be composed of vegetables such as squash (of any type), green beans, pea pods, tomatoes, broccoli, okra, carrot, cooked sweat potato, and fruits such as papaya, mango, berries, melon and banana.  The more items that are mixed together, the greater the chances that proper nutrition is covered adequately. *Consult the section of this handout on calcium-phosphorous content of selected foods).


There are many experts that feel that supplements are not needed in a properly fed iguana.  My feeling is that so few iguanas are properly fed, that supplements are often of some benefit, especially during the juvenile stages of rapid growth.  Below are some basic guidelines.  These guidelines are not true for pets that are on commercially prepared diets (often the supplements are built in).  If you are unsure, consult your veterinarian.  Also in cases of nutritional disease you may be instructed to use different guidelines.


Calcium/Vitamin D tablets: For baby and adolescent iguanas use a chunk the size of their eye every other day.  For adult iguanas use the same amount, 1-2 times a week.  Chewable tablets are accepted more readily.

Calcium/Vitamin D powder: For babies and adolescents use approximately 1/16 tsp. per every 6 inches of body length (excluding the tail) every other day.  For adults, same amount, only 1-2 times a week.

Calcium only supplement: This is probably preferable for daily or frequent use as it is less likely to cause overdose of Vitamin D.  Neocalglucon is a readily available safe source of calcium that comes as a palatable liquid.  Use approximately 0.10cc per each 100-200 grams of body weight daily or every other day in babies and juveniles.  Use the same, 1-2 times a week in adults.  Crushed Tums (calcium carbonate) is another good calcium-only source.

Multivitamin supplement: For babies and adolescents use approximately 1/16 tsp. per every 6 inches of body length (exclude the tail) every other day.  For adults, same amount, only 1-2 times a week.

Remember, the more balanced and varied your pets natural diet is, (especially if at least 75% of the food items are from the list of good calcium sources off the calcium chart), the less dependent your pet will need to be on supplements.  Supplementation of vitamins and minerals is not a substitute for a good diet, and may lead to disease problems.  Provide a warm environment with exposure to natural sunlight, if possible, to further enhance your chances of successful assimilation of nutrients.


The following charts show the total amount of calcium and phosphorous in 1-cup portions of selected foods.  One need not look only at the total milligram (mg) amount of calcium, but also the Calcium:Phosphorous ration.  This ratio should be close to 1:0.5 for the best calcium absorption.  The higher the phosphorous amount compared to the calcium, the poorer the absorption of calcium in the body.


1 cup portion                                                           Calcium                  Phosphorous                           Ca:P Ratio


Turnip greens                                                          106                          24                                            1:0.2

Chinese Cabbage                                                      74                            26                                            1:0.4

Mustard Greens                                                       104                          58                                            1:0.3

Leeks                                                                       60                            36                                            1:0.6

Watercress                                                                                               40                                            20            1:0.5

Chard                                                                       102                          58                                            1:0.5

Collards (cooked)                                                    148                          19                                            1:0.1

Kale                                                                         98                            36                                            1:0.4

Dandelion Greens                                                    104                          36                                            1:0.3

Endive                                                                     23                            14                                            1:0.6

Beet Greens                                                             164                          58                                            1:0.4

Dark Green Leaf Lettuce                                          28                            14                                            1:0.5

Parsley                                                                     78                            24                                            1:0.3

Spinach                                                                    56                            28                                            1:0.5

Yellow wax beans                                                    174                          34                                            1:0.2

Blackberries                                                             46                            30                                            1:0.6

Papaya                                                                     72                            16                                            1:0.2


Cabbage (inside white leaves)                                  46mg                       34mg                                       1:0.7

Strawberries                                                             42mg                       56mg                                       1:1.3

Turnips                                                                    36mg                       30mg                                       1:0.8

Okra                                                                        100mg                     90mg                                       1:0.9

Raspberries                                                              27mg                       15mg                                       1:0.5

Green Beans                                                            58mg                       48mg                                       1:0.8

Guavas                                                                    18mg                       23mg                                       1:1.3

Apples                                                                     10mg                       10mg                                       1:1

Pears                                                                        15mg                       18mg                                       1:1.2

Mango                                                                     21mg                      22mg                                       1:1

Radish                                                                     24mg                       20mg                                       1:0.8

Eggplant                                                                   30mg                       26mg                                       1:0.8

Romaine Lettuce                                                      20mg                       26mg                                       1:1.3



Parsnips                                                                   58                            108                                          1:1.9*

Rutabaga                                                                  72                            84                                            1:1.2

Blueberries                                                              18                            30                                            1:1.6

Squash (summer all varieties)                                  26                            46                                            1:1.8*

Zucchini                                                                  20                            42                                            1:2.1*

Carrots                                                                     28                            64                                            1:2.3*

Cantaloupe                                                               17                            27                                            1:0.9

Yams                                                                       18                            66                                            1:3.6*

Apricots                                                                   15                            21                                            1:1.4

Plums                                                                      4                              14                                            1:3.5*

Beets                                                                        18                            26                                            1:1.4

Cherries (pitted)                                                       10                            13                                            1:1.3

Cauliflower                                                              28                            46                                            1:1.6

Grapes                                                                     13                            9                                              1:0.7

Peaches                                                                    5                              11                                            1:2.2*

Cucumber                                                                14                            18                                            1:1.3

Pumpkin                                                                  36                            74                                            1:2.1*

Sweet potato                                                            64                            124                                          1:1.9*

Lettuce (head, iceberg)                                             16                            16                                            1:1.0

Asparagus                                                                44                            108                                          1:2.5*

Tomato                                                                    16                            58                                            1:3.6*

Pineapple                                                                 11                            11                                            1:1.1

Bananas                                                                   7                              22                                            1:3.1*

Peas (any kind)                                                        38                            168                                          1:4.4*

Brussel Sprouts                                                       56                            88                                            1:1.6


1 cup portion                                                           Calcium                  Phosphorous                           Ca:P Ratio

Mushrooms                                                             4                              72                                            1:18*

Corn                                                                        10                            120                                          1:12*

Alfalfa sprouts                                                         20                            46                                            1:2.3*

Beets                                                                        26                            42                                            1:1.6

Kidney beans                                                           100                          504                                          1:5*

Lima beans                                                              64                            416                                          1:6.5*

Bean sprouts                                                            14                            56                                            1:4*

White potato                                                            16                            104                                          1:6.5*

Green Peppers                                                         6                              22                                            1:3.6*

If you are feeding a pet that needs a good calcium source (such as iguanas or other herbivorous lizards), feed at least 75% of the diet selected from the good calcium source table.  Feed only small amounts from the moderate and poor calcium source groups.

If you are instructed to feed your pet a diet that is low in calcium, then concentrate on foods in the poor and moderate calcium sources groups or choose those in the high calcium group that have a low milligram amount of calcium.  If your pet is also on a calorie restricted diet, consult your veterinarian for exact amounts to feed (some of these foods may be high in calories).

Foods marked with an asterisk (*) SHOULD BE AVOIDED IN ANIMALS WITH KIDNEY DISEASE due to their high phosphorous content.

Calcium and phosphorous values were adapted from Bowes and Church’s Food Values of Portions Commonly Used revised by Jean A.T. Pennington, Ph.D., RD  15th edition.  Published by Harper Perennial 1989.  Pages 94-102 and 190-211.


A humidity box can be an excellent way to provide the proper moisture required in the environment of a number of reptile and amphibian species.  This is important to help the pet shed its skin normally, and can be accomplished without making the entire cage too moist.  The box can also serve as a hiding place, helping with the mental wellbeing of the pet as well as a soaking area.  The box is simple to construct and maintain, and has proven to be most useful to such species as iguanas, prehensile tailed skinks, snakes (especially ball pythons), and some amphibians such as tree frogs.

To construct a humidity box one needs to purchase:

  1. Sphagnum moss – sold in packets in a dry form in most large garden center stores.  It is brown in color and consists of long strands.  Alternatively one may use Vermiculite which is more of a granular product (found also in garden centers), but has the disadvantage that it tends to stick to the pet and subsequently get dragged around the cage.
  2. Plastic box with a lid – of the appropriate size for your pet.  The box should be of such a size that the pet can enter the box, turn around and exit through the same opening.  The fit should be fairly snug.  If the box is too large, there may be a tendency for the pet to defecate in the corner.

Making the box:

  1. Cut a hole in the lid of the box or at one end of the box.  The hole should be large enough for the pet to enter and leave the box easily.  No other holes should be put in the box, or the contents may dry out too quickly.
  2. Loosely pack the box with the dry sphagnum moss, and then wet it down with water.  If Vermiculite is being used, fill the box about ½ full and moisten it in the same manner.  Let the moss sit for 10 to 15 minutes to absorb the water, then pick it up in handfuls and squeeze out the excess water as you would a sponge.  Pour off any excess water in the box, and replace the moistened moss and the lid.  Viola!  You have the finished product.
  3. Place the box in the cage near a heat source.  No more than half of the box should be over the heat or it will dry too quickly.  If it is not warmed at all, the reptile will not be comfortable in it.  Place the pet in it once, then let it enter and leave the box as it wants.  Many people note that their pets will spend hours in the box at a time and then ignore it for long periods.  Let your pet decide.
  4.  Check the moisture content and the cleanliness of the box every 1-2 days.  If the animal does not defecate or take food particles in the box, the moss may stay clean for up to 2 weeks.  If there is any of a stale odor, fecal material or any other debris in the box remove the moss and replace with clean moss.  The box should be disinfected periodically by filling it with a mild bleach solution and letting it stand for 30 minutes.  Additional moisture can be added between moss changes by spraying the moss with water.

Photograph © Jason R. Weigner