Green Iguana

About the species

The green iguana (Iguana iguana) is one of the most recognisable lizards in the world, and also one of the terrarium animals most often bought on impulse without much research beforehand. It comes from the tropical and subtropical regions of Central and South America, where it lives in tree canopies along rivers and lakes, basks on branches overhanging water, and swims strongly – when threatened, it will simply drop into the water or fall from a branch, usually surviving falls of up to around 15 metres unharmed. Among lizards, it is one of the most commonly kept pet species in EU countries.

Pet shops typically sell it as a hatchling only 20–30cm long, so many buyers do not anticipate how quickly, and how large, it actually grows. That gap between expectation and the real adult animal is a major reason why green iguanas are so often surrendered or rehomed once they outgrow their first enclosure.

How big it really gets

A full-grown green iguana can reach a total length of around 2 metres, occasionally a little more, roughly two-thirds of which is tail – the body itself, from snout to vent, is typically only about 30 to 45cm. Males tend to be larger than females and can weigh 6–8kg, while smaller females weigh around 1.5–3kg. Sex is difficult to determine reliably in young animals from external features alone, since the differences between males and females only become obvious at sexual maturity, at around 2 to 4 years old. All of this means an enclosure that suited a hatchling becomes too small within two or three years of growth; an adult needs housing that is often larger than many rooms, and taller than it is wide, since iguanas are arboreal and spend most of their time on branches in the upper part of the enclosure.

Diet and the protein risk

Adult green iguanas are strict herbivores. A daily meal should consist of varied, fresh, calcium-rich vegetables (such as dandelion greens, plantain, parsley, turnip or beet greens) plus a smaller portion of fruit, chopped into pieces no bigger than roughly twice the distance between the animal's nostrils, with fresh drinking water offered every day. Juveniles under about 60cm sometimes take a small amount of animal-based food, such as insects, in the wild and occasionally in captivity. In adults, feeding animal protein (meat, cat or dog food, too many insects) is risky, because an iguana's digestive system is not built to process animal protein efficiently – sustained overfeeding of protein can strain the kidneys and lead to kidney damage.

Housing, temperature and UVB

Green iguanas need strong UVB lighting (both UVA and UVB) to process dietary calcium properly. A suitable daytime enclosure temperature is roughly 27–32°C, dropping to 19–25°C at night, with anything below 17°C considered harmful; many care guides also recommend a distinctly hotter, localised basking spot. Humidity should generally sit between 60 and 90%. An adult's enclosure needs a water basin large enough to soak in, sturdy branches for climbing and resting, and heating elements positioned so the animal cannot burn itself on them; any live plants used as furnishing need to be non-toxic, since an iguana will readily chew on the foliage.

Temperament and handling

Green iguanas are strong-willed, territorial animals that are not domesticated in the way a dog or cat is, and they require patience, consistency and a real understanding of their behaviour from their owner. They communicate and assert dominance through head-bobbing and by extending the dewlap under the chin, and sexually mature animals, especially unneutered males, can become noticeably more aggressive and territorial during the breeding season. Their main defence is a powerful tail-whip, and their climbing claws are sharp, so careless or forceful handling can result in scratches or cuts; regular, calm handling from a young age makes later handling considerably easier.

Outside its native range

Because of its popularity in the exotic pet trade, released or escaped green iguanas have established self-sustaining populations outside their native range in a number of places, notably Florida and several Caribbean islands, where they are considered an invasive species that damages native plants and undermines canals, levees and similar structures with their burrows. That is not a concern for a responsibly kept terrarium animal, but it is a good illustration of just how adaptable and long-lived the species is – which again comes back to the genuine long-term commitment it asks of an owner.

Health, CITES and legal status

International trade in green iguanas is controlled under CITES, where the species is listed on Appendix II, and the EU's own wildlife trade regulation applies alongside it. Crossing an external EU border with one requires the relevant CITES permit or certificate. In Slovenia specifically, acquiring a green iguana must be reported in writing to the Slovenian Environment Agency (ARSO) within 30 days. As with all reptiles, there is a risk of salmonella transmission, so washing your hands after handling is advisable. Common signs of illness include reduced activity, changes in skin colour, swollen limbs or lower jaw, and a persistent cloacal prolapse – any of these warrant a vet visit, which is also worth scheduling routinely soon after acquiring the animal.

Pros & cons