Feeding a green iguana: which greens for a strict herbivore?
The green iguana (Iguana iguana) is one of the few large herbivorous lizards commonly kept in captivity, and its diet changes markedly with age. A reference study by Troyer, published in 1984 in Oecologia, showed that the species' food selection and digestive efficiency depend closely on age and nutrient requirements, with young iguanas digesting differently from adults as hindgut fermentation gradually develops (research on Google Scholar). Find our other pointers in the food section.
A base of dark leafy greens, never pale lettuce
Dandelion greens, mustard greens, endive, hearty mixed salad greens and edible flowers (hibiscus, pansy) form the base of a balanced meal. Iceberg or pale lettuce, too watery and nutrient-poor, should never make up the bulk of the bowl, even if the iguana readily eats it.
The calcium-phosphorus ratio: a pointer worth knowing
Greens offered should show a favourable calcium-phosphorus ratio, ideally above 1:1 in calcium. Spinach and beet greens, rich in oxalates that block calcium absorption, should stay occasional rather than regular. This chronic imbalance is the central mechanism behind metabolic bone disease, covered in our article on the green iguana and metabolic bone disease.
Fruits and foods to sharply limit
A little fruit (papaya, fig) can round out a meal in small amounts, never as a base. Excess cabbage and broccoli, through their goitrogenic effect on the thyroid, and avocado, toxic to many reptiles, should be avoided or strictly limited depending on the species within that family.
Practical pointers
- At least 90% plant-based in adults: varied dark leafy greens, never the same single species on repeat.
- Favourable calcium-phosphorus ratio: limit oxalate-rich spinach and beet greens.
- Fruit in small amounts only, never as a dietary base.
- Avocado off the menu, excess cabbage and broccoli avoided.
A properly sized terrarium supports this herbivorous diet by making feeding spots easy to reach; our article on the green iguana's growing terrarium details how to plan for its growth. See also our green iguana profile for its full picture.
Frequently asked questions
Can a green iguana eat insects?
In the wild, young individuals sometimes eat them opportunistically, but in captivity the adult's diet should stay strictly plant-based to avoid excess animal protein, which is hard on the kidneys.
Does it need calcium supplementation at every meal?
Regular dusting is generally recommended, especially if the terrarium's UVB isn't flawless; the exact frequency should be set with an exotics vet based on the animal's age.
Is iceberg lettuce dangerous?
Not toxic, but too nutritionally poor to serve as a base: it dilutes essential nutrient intake without offering much in return.
This guide is part of Planète Pets’s Reptiles universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.