Green Iguana Facts

The green iguana belongs to the kingdom Animalia, phylum Chordata, class Reptilia, and order Squamata. Within that order it is part of the family Iguanidae, a group that includes several herbivorous lizards with clawed limbs. The scientific name Iguana iguana is a tautonym derived from the Taíno word "iwana."

The Iguanidae lineage extends back millions of years. Green iguanas differ from many insect-eating or carnivorous lizards through a combination of arboreal traits and a plant-based diet. Their claws and toes support movement through the canopy, while microbes in the digestive tract help break down fibrous plant matter.

Green iguanas are large reptiles with visible sexual dimorphism. Mature males are larger, often more brightly colored, and have more pronounced dorsal spines and jowls than females. Adults usually measure 1.2 to 1.8 meters (4 to 6 feet) in total length, although some males approach 2 meters. The tail can account for up to two-thirds of that length, and adults generally weigh 4 to 9 kilograms (9 to 20 pounds).

Color varies with age, location, and sex. Juveniles are often bright green, while adults may be olive, gray-brown, orange, or blue; dominant males can become more colorful during the breeding season. A row of flexible keratin spines runs along the back and tail, altering the body outline and discouraging bites along the spine.

The dewlap beneath the chin contains many blood vessels and is used in thermoregulation, territorial displays, and courtship. Long toes end in curved claws that grip bark. The eyes provide color vision and detect ultraviolet wavelengths. A photosensitive parietal eye on top of the skull cannot form detailed images but detects changes in light and shadow, including the movement of aerial predators.

The native range of the green iguana extends from northern Mexico through Central America and into South America, including Colombia, Ecuador, Peru, and Brazil. Native populations also occur on Caribbean islands, including Curaçao and parts of the Lesser Antilles.

Green iguanas inhabit tropical forest, cloud forest, and coastal shrubland, often near water. They are primarily arboreal and commonly use trees over slow rivers, oxbow lakes, and mangrove swamps. These locations provide basking sites, foliage, and an escape route into water.

Unlike many insect-eating or carnivorous lizards, the green iguana is primarily herbivorous. Its diet consists mainly of leaves, flowers, fruit, and young shoots.

Leaves contain cellulose that vertebrate enzymes cannot digest directly. The iguana's elongated hindgut acts as a fermentation chamber populated by symbiotic microbes, which break down plant fibers and make nutrients available to the animal.

Microbial fermentation works more efficiently when the iguana is warm, so individuals often bask in the morning before feeding. Serrated teeth shear leaves from stems. Green iguanas obtain much of their water from foliage and fruit and may drink standing water less often.

Green iguanas may bask near one another but do not form stable cooperative groups. Mature males can be territorial, particularly during the breeding season.

A dominant male establishes and defends a territory, usually a large tree with good basking sites and access to females. When a rival intrudes, the defending male compresses his body to appear larger, extends his dewlap, stiffens his legs, and performs rapid head-bobbing. If the intruder does not retreat, the encounter may escalate to tail strikes, biting, and wrestling that can cause injury.

When threatened by a bird or climbing snake, an iguana may remain motionless in the foliage. If detected, it can drop from the canopy—sometimes 40 feet or more—into water. While swimming, the legs fold against the body and the tail provides propulsion; an iguana can remain submerged for up to 30 minutes. On land, the tail, claws, and teeth provide defense. If a predator grips the tail, a break can occur at a fracture plane in the vertebra, allowing escape; a shorter cartilaginous replacement may grow later.

Green iguana reproduction follows the wet and dry seasons. Mating usually occurs in the dry season, and eggs hatch near the start of the wet season when new foliage is available.

After mating, the female descends to find soft, sun-exposed soil and digs a burrow that can exceed one meter in depth. She lays 20 to 70 leathery eggs, covers the nest, and returns to the canopy without providing further care.

Ambient heat incubates the eggs for approximately 90 to 120 days. Hatchlings use an egg tooth on the snout to cut through the leathery shell. Young iguanas often remain near one another in low vegetation before moving higher into the canopy as they grow. Juvenile mortality is high, while individuals that reach maturity can live 10 to 15 years in the wild.

(Population and conservation trend data sourced from the IUCN Red List of Threatened Species)

The green iguana is classified as Least Concern on the IUCN Red List, and its global population trend is considered stable. A broad native range and relatively large clutches reduce the effect of localized declines on the species as a whole.

Local populations can still decline. In parts of Central and South America, green iguanas are hunted for meat, sometimes called "gallina de palo" (chicken of the trees), and their eggs are collected for food. Sustained harvest can reduce the number of breeding females.

Deforestation removes canopy habitat, and the international pet trade includes both captive breeding and illegal collection. Outside the native range, introduced populations in places such as Florida, Hawaii, and Puerto Rico damage vegetation and compete with native species. Management therefore differs by region: habitat and harvest controls apply within the native range, while introduced populations may require removal or containment.

• San Diego Zoo Wildlife Alliance - Green Iguana
• National Geographic - Green Iguana Facts
• IUCN Red List of Threatened Species - Iguana iguana
• World Wildlife Fund (WWF) - Amazon and Neotropical Ecosystems