Green Iguana (Iguana iguana): Facts, Habitat and Diet

What does a green iguana look like?

The green iguana is a long, heavy lizard with strong legs, sharp curved claws and a tail that makes up more than half of its total length. A crest of soft, pointed spines runs from the neck down the back and onto the tail. The spines are longer and thicker in adult males.

Under the throat hangs a large flap of skin called a dewlap. Thin rods of the hyoid bone, part of the throat skeleton, can pull it forward like a sail. The iguana extends its dewlap to warn rivals, impress females and scare predators, and it also helps the animal gain or lose heat.

Below each ear opening sits a large, round, shiny scale known as the subtympanic plate. On top of the head, between and slightly behind the eyes, is a small pale scale that covers the parietal eye, a light-sensing organ explained in Do iguanas have a third eye?.

The teeth are small, leaf-shaped and finely serrated, ideal for slicing leaves. Their shape inspired the name of the dinosaur Iguanodon (“iguana tooth”) in the 1820s, which was first imagined as a giant iguana.

Color: are green iguanas always green?

Despite their name, green iguanas vary a great deal. Hatchlings are usually bright green, sometimes with darker bands. As they grow, many become duller green or gray, and regional forms can be bluish, reddish, orange, lavender or nearly black. Iguanas on some Caribbean islands, such as Bonaire and Saint Lucia, are especially distinctive.

An individual can also change shade, though slowly and far less than a chameleon. Iguanas look darker in the cool morning, which helps them absorb sunlight, and paler in the midday heat. Dominant males are often darker than lower-ranking ones, and in the weeks before and during the breeding season many males turn orange or gold. Females mostly stay green.

How big do green iguanas get?

The green iguana is the largest lizard in the iguana family by length, although some Caribbean rock iguanas (Cyclura) can be as heavy. It is also the largest lizard living wild in the United States, where it is an introduced species.

Growth is fast at first: a hatchling weighing about 12 g (0.4 oz) can reach roughly 1 kg (2.2 lb) within three years. Males keep growing for longer and end up clearly larger than females, with bigger heads, jowls, dewlaps and spines.

Where do green iguanas live?

The native range of the green iguana runs from Mexico through Central America to Paraguay and southern Brazil, and includes many Caribbean islands. Within this range it lives mainly in humid lowland forest, especially in tall trees along rivers, lakes, swamps, mangroves and coasts. It also adapts well to drier open woodland, farmland, parks and town gardens.

Water nearby is important. Green iguanas bask on branches hanging over rivers, and when danger appears they simply let go and drop into the water. Young iguanas tend to stay lower in the vegetation, while large adults use the higher canopy.

People have spread the species far beyond its natural range, mostly through the pet trade. Wild populations are established in South Florida, Puerto Rico, the U.S. Virgin Islands, Hawaii, the Rio Grande Valley of Texas, several Lesser Antilles islands, Fiji, Taiwan, Singapore and Thailand. The Florida story is covered in Are iguanas invasive in Florida?.

What do green iguanas eat?

Green iguanas are herbivores. In the wild they eat leaves, flowers, fruit and young shoots from well over 100 plant species, with leaves making up most of the diet. In Panama, for example, the fruit and leaves of the wild hog plum (Spondias mombin) are a favorite. They occasionally swallow insects, snails, bird eggs or carrion, but this is a small and irregular part of what they eat.

Plants are hard to digest, so iguanas rely on helpful microbes in an enlarged hindgut that ferment plant fiber. Young iguanas acquire these microbes by eating the droppings of older iguanas. Because leaves contain a lot of potassium and salt, iguanas also have a nasal salt gland that removes extra salts, sometimes with a little “sneeze.” For the full picture see What do iguanas eat in the wild?.

Behavior: climbing, swimming and basking

Green iguanas are active by day and spend much of it basking, because, like all reptiles, they depend on outside heat to warm their bodies. They are agile climbers and are famous for surviving falls of up to about 15 m (50 ft) without injury, grabbing at leaves and branches with their hind claws to slow the drop.

In the water an iguana stays mostly submerged, holds its legs flat against its body and swims with powerful sweeps of its tail. It can stay underwater for several minutes to hide from predators.

Although they live in trees, green iguanas are also capable diggers. Burrows range from about 0.3 to 2.4 m (1–8 ft) deep. In Florida they dig into canal banks, levees and the soil behind seawalls, and sometimes take over burrows dug by gopher tortoises or burrowing owls.

When cornered, an iguana puffs up its body, extends its dewlap, hisses and bobs its head. If that does not work it lashes with its tail, bites and scratches. Like many lizards, it can shed part of its tail if grabbed and later grow a shorter replacement, a trick explained in why lizards drop their tails.

Iguanas communicate mostly through body language. Head bobs of different speed and number mean different things, from a greeting to a territorial challenge.

Reproduction and life cycle

Green iguanas breed once a year, usually in the dry season, so that the young hatch at the start of the rainy season when fresh plant food is plentiful. Males defend territories with head bobbing, dewlap displays and tail whipping, and mark branches and rocks with a waxy scent from pores on the underside of their thighs, called femoral pores.

About two months after mating, the female digs a nest burrow, often 45 cm (18 in) to more than 1 m (3.3 ft) deep, in sandy soil. She lays a single clutch of leathery eggs, usually a few dozen; reported clutch sizes range from about 10 to 70 eggs, with larger females laying more. Where good nest sites are scarce, many females nest in the same area, and in Panama green iguanas have even been seen nesting alongside American crocodiles.

The female gives no care after laying. The eggs hatch after roughly 10–17 weeks, depending on temperature. Hatchlings look like small, plain green adults and often stay together in loose groups during their first year, which may help them spot predators. Most green iguanas reach breeding age at 2–4 years.

How long do green iguanas live?

Green iguanas are thought to live about 8 years on average in the wild, because eggs, hatchlings and young are eaten by many predators. In captivity, protected from predators, they can live for more than 20 years.

Predators and threats

At least 108 kinds of vertebrate are known to prey on green iguanas, especially the young. Hawks, herons, snakes such as boas and vine snakes, larger lizards, crocodilians, wild cats and other mammals all take them. Adults rely on size, spines, sharp claws, a powerful tail and a quick escape into water.

People are the main threat in parts of the native range. Iguana meat and eggs have been eaten in Central and South America for thousands of years; the animal is nicknamed gallina de palo, “chicken of the tree.” Heavy hunting has made it scarce in some areas, and Nicaragua and Panama introduced controls on the trade decades ago. Habitat loss and capture for the international pet trade add further pressure.

Conservation status

The green iguana is listed as Least Concern on the IUCN Red List (assessment published in 2022) because it is widespread and still common in much of its range. International trade is regulated under Appendix II of CITES, the treaty on trade in wild species. Some island forms in the Lesser Antilles are genetically distinct, and scientists are still debating whether they should be treated as separate species, which could change their conservation status.

Green iguanas and people

The green iguana has been one of the most heavily traded reptiles in the world, with hundreds of thousands imported into the United States each year in the 1990s, mainly from farms in Central and South America. Many pet iguanas were later released or escaped, which helped create the wild populations now found in Florida and elsewhere.

Where the species is introduced, it can damage gardens and native plants, and its burrows can weaken seawalls and canal banks. In South Florida, very cold nights occasionally leave iguanas so chilled that they drop from trees, a phenomenon explained in Why do iguanas fall from trees?.

The green iguana is often confused with its relatives. The marine iguana of the Galápagos is a different species that feeds on seaweed, while spiny-tailed iguanas (Ctenosaura) share some of the same Central American habitats but have rings of spiny scales on the tail.