Be Careful of What You Feed to Your Green Iguana

Photo by Chris Estep and Wendell Leopard  

Or He May Look Like This!!


Table of Contents

Natural History

Green iguanas (Iguana iguana) are large semi-arboreal to arboreal lizards of the primarily New World Americas. They are almost an exclusively herbivorous reptile. Earlier beliefs were that the juveniles were insectivores, and then gradually grew into herbivorous adults. However recent studies on stomach content in wild iguanas have revealed that this is not the case. Iguanas are born herbivores and do not go through an ontogenetic shift from insectivore to herbivore. The digestive system is therefore designed to digest plant materials and not, as some recommend, to digest meat in any amount. The green iguana has evolved an elaborate hindgut, housing a microbial fermentation system that allows it to utilize fiber as effectively as mammalian ruminants. The adult iguanas spend most of their time in the upper parts of the trees, while the juveniles are either on the ground or in the lower parts of the trees and bushes. Due to the iguana's habitat, its wild diet consists of a variety of leaves, small fruits and flowers - and this variety should be provided in captivity as well. It may sound easy to provide a varied diet for the captive iguana, however the diet must also be a nutritiously balanced and healthy diet and this is why the iguana owner needs to learn some basic guidelines for making a proper Iguana-salad.
Photo by Chris Estep

Feeding Ethics

Iguanas don't recognize what we are trying to feed them as being proper food. They are attracted by certain shapes and colors, and may, like humans, get 'hooked' on junk foods, foods that either lack nutritional value or that are downright harmful to them, or foods that they are simply used to getting. This is a particular problem with pre-owned iguanas, iguanas being fed less than ideal diets, and those who have come from pet stores where they have been fed the generally inappropriate feed usually fed to them. One needs to learn how to deal with this syndrome, how to be patient, not give in, and eventually be rewarded with your iguana eating what it should!

Dietary Adjustment

There is no simple answer as to what is the best diet for iguanas. Green iguanas are hardy and extremely adaptable and will fare on a wide variety of different diets as long as they all meet a certain basic criteria. When keeping an iguana as a pet, one of the best ways to adjust the diet is to look at the veterinary problems with the associated with the diet at different stages in an iguana's life.

From The Green Iguana Manual by Philippe de Vosjoli

Recommended Diet and Feeding Schedule:

For juveniles up to 2½ years of age:

Feeding Schedule: Daily. Twice daily or continuous availability for hatchlings.
Diet: 85-90% plant matter
        10-15% animal protein sources and/or commercial pet diet
Vitamin/Mineral Supplementation: One small pinch of vitamin/mineral supplement per animal,
                                                     no more than once a day.

For iguanas 2½ years and up:

Feeding Schedule: Every 1-2 days
Diet: 95% plant matter
        5% animal protein sources and/or commercial pet diet
Vitamin/Mineral Supplementation: One full pinch per 2 lbs twice a week or 1/8th of a
                                                     teaspoon per 3-4 lbs of body weight per week.

Note: For mature females, increase calcium supplementation and protein sources
          (up to 15%) starting in late December and through egg-laying.

Edible and Toxic Foliage

Before you go about preparing a salad for your iguana, one of the first things the you as an owner of an iguana needs to learn is to distinguish between "good" and "bad" food. The "good" foods are those food items that can be fed on a daily basis, ones listed in the Basic Iguana Diet.  If you plan to have the iguana free roaming in the house it is a necessary to find out what plants can be placed in the home. Only those that are non toxic should present.  Please refer to Melissa Kaplan's Edible Plants page to determine which house plants are safe to have accessible to the iguana.
There are also those plants which should either be avoided or only be used occasionally (ones every other week).  Some of these include: spinach, romaine lettuce, onions, beets, beet greens, celery stalk, Swiss-chard, carrots, bananas, grapes, lettuce, kale, Chinese cabbage, broccoli, turnips, cauliflower and brussels sprouts.  However there are some plants that are to be avoided all together. These plants are not edible and may have severe toxic consequences for the animal. Rhubarb is extremely toxic because of the formation of calcium oxalate crystals. For a complete list of plants toxic to iguanas and their pathways of toxicity, please refer to Melissa Kaplan's Harmful Plants complete listing. However, if you would like to view the plants for visual identification you can see the plants at the Cornell University pages of Poisonous Plants. If your reptile does ingest something it should not have, watch it carefully for signs of distress. Signs will usually include respiratory changes (i.e. rate of breathing increases or decreases, breaths become shallower or deeper, breathing becomes labored or difficult), increased salivation, dry heaves, vomiting, lethargy, increased activity, rubbing mouth on ground or other surfaces, scratching at face or mouth, diarrhea or other alteration of feces. Don't wait to see if the signs will abate - call (or have someone call) your regular reptile vet or emergency reptile vet (have these numbers and locations on hand before you need them) and let them know what the animal ate, what the signs are, and that you are on your way.  The National Animal Poison Control Center may also be able to offer you pertinent information, but in a potential emergency where time is of the essence, you should get your reptile to a vet who can administer an antidote and supportive therapy as quickly as possible. 

A Well Balanced Diet

Calcium Rich Vegetables, where the Ca : P > 2 - 35% or more of the diet.

Other Vegetables: A variety weekly - 35% or more of diet.

Grain/Fiber sources: Optional - up to 20% of diet.

Fruits: Offer a variety weekly - No more than 15% of diet.

Animal Protein sources: Up to 15% for hatchlings and sub adults. No more than 5% of adult diet.

  • Insects: Crickets, meal worms, king meal worms
  • Meats: Cooked chicken, small pre killed mice
  • Commercial pet diet: Soaked high quality dog or monkey chow
  • Other: Hard boiled eggs
We receive a large volume of mail about feeding iguanas meat. A large vocal group of iguana fans oppose this despite the fact that iguanas can and do eat meat in the wild and in captivity. As stated above, animal protein should be NO MORE THAN 5%. Please do not email us further about this.

Photo by Chris Estep

  Basic Iguana Diet and Preparation
  Greens (30-40% of volume)

Romaine    Kale     Leaf Lettuce    Collards    Spinach    Escarole    Mustard Greens    Parsley, etc.

    Handling:     All greens thoroughly rinsed and chopped or diced. Hatchlings or juveniles
                        need finely chopped food to aid digestion. Gut Fauna in young iguanas can
                        be overwhelmed by the large pieces of food.

Bulk Vegetables (30-40% of volume)

Frozen mixed vegetables (carrots, corn, peas, limas)    Green beans     Zucchini    Cabbage Peas        Avocado        Broccoli        Yams

    Handling:    All vegetables should be fresh or frozen: thawed and served room temperature
                       or slightly warm, chopped.

Fruit (10-30% of volume)

Banana    Melon (Honey dew, Cantaloupe, etc.)    Kiwi    Grapes    Papaya    Mango Strawberries       Cherries        Blueberries        Peaches

    Handling:    All fruit washed and chopped into small pieces designed to be bite-sized for
                        various size iguanas.  Bananas served with skin.

Protein (1-5% of volume)

       Cooked chicken                                                                                 Dog or Monkey chow

    Handling:    Chicken meat chopped. Process food soaked.
  guana Diet Chart by Robert Ehrig of the International Iguana Society

  Nutritional Disorders in Green Iguanas

Deficiency/ Metabolic Bone Disease
Calcium deficiency is the lack of physiologically available calcium. Simply supplementing the diet with calcium will not assure that the calcium will be absorbed through the lining of the intestine and become usable. For the effective absorption of calcium through the intestinal lining an adequate amount of vitamin D3 and the proper calcium/phosphorus ratio is required. It is recommended that in iguanas that minerals be provided in the ratio of 1 part D3 to 2 parts calcium to 1 part phosphorus.  These can be added in the form of vitamin supplements such as Rep-Cal® and Terrafauna Vitalife® using the proper dosage.
Secondary Causes:
Calcium deficiency can also be caused by the excessive feeding of oxalic acid. When ingested, oxalic acid has a high affinity for blood calcium. This causes a reduction of calcium levels as well as the formation of a potentially lethal, insoluble substance Calcium Oxalate. Refer to Melissa Kaplan's chart on the oxalate to calcium ratio of selected iguana foods to determine a suitable diet for your pet.  Acute cases of ingestion of high levels of oxalic acid is potentially lethal. The deposition of the crystals in the kidneys will cause blockage, necrosis, and ultimately death. One plant to avoid at all costs is Rhubarb. The high content of oxalic acid in the rhubarb leaves are toxic will kill even the largest of the iguanas. 
The symptoms of metabolic bone disease will vary depending on a number of factors, such as the age of the animal and duration of the disease. In juveniles, symptoms can include a soft lower jaw and deformities of the back and legs. In larger animals, osteoporosis and fibrous osteodystrophy may occur. These are characterized by the swollen, smooth appearance of the hind limbs and swollen lower jaw. Animals with fibrous osteodystrophy are often initially perceived as rotund, fat animals until they manifest abnormal behaviors, usually the result broken limbs and bones now too weak to support the weight of the animal. Fibrous dystrophy results in swollen limbs due to the deposition of scar tissue around the ever-weakening and thinning bones to make up for the structural weakness.


Visceral gout is a disease caused by the accumulation of urate crystals and characterized by the presence of particular lesions called "tophi". In captive herbivorous reptiles, the primary cause is excessive animal protein in the diet. It is a common cause of death in older iguanas fed a primarily high meat or canned dog food diet.  The feeding of meats high in purines have been closely associated with high urate levels in herbivorous reptiles. A secondary cause is the lack of water which is needed to by the iguana to flush out uric acid derivatives. Once present, visceral gout is usually fatal.

Mineralization of Internal Organs/Metastatic Calcification
Once an iguana matures and growth rate tapers, excessive calcium in the diet will be readily absorbed into the blood stream with high levels of vitamin D3 and can accumulate in various internal organs. Over time this will eventually kill the animal. Care must be given to not over supplement the diet of adult iguanas. It is recommended that 100-200 IU/ of D3 per kilogram (2.2 lb) be fed per week. The moral is that too much of a good thing is not always better. 

Popular Iguana Links


1.    Boyer, T. 1991. Common problems and treatment of green iguanas (Iguana iguana).
            Bulletin of the Association of Amphibian and Reptilian Veterinarians.
            Vol. 1 No. 1. pp. 8-11.

2.    Frye, F. 1991. A Practical Guide for Feeding Captive Reptiles. Kreiger Publishing.
            Malabar, Fl.

3.    Troyer, K. 1983. Diet selection and digestion in Iguana iguana, the importance of age
            and nutrient requirements. Oecologia (Berlin) 61:201-202.

4.   Vosjoli, Philippe. 1992. The Green Iguana Manual. Advanced Vivarium Systems.
            Lakeside, Ca.

[Top of Page][Natural History][Feeding Ethics][Dietary Adjustment] [Feeding Schedule][Edible and Toxic Plants][Well Balanced Diet][Basic Diet and Preparation] [Nutritional Disorders][Popular Iguana Links][Acknowledgments]

This page is dedicated to Jurassic, my wonderful green iguana. - Ben Brault

This series of web pages was created by Ben Brault, an undergraduate student at Cornell University for the AS625 class. All comments and suggestions are welcome.

WARNING: These web pages are only meant to be informative. Neither Cornell University nor the author of this site endorse or recommend the use of these plants.

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