Green iguana

The green iguana (Iguana iguana) is a large, arboreal lizard.

This means they spend much of their lives in trees. They are mostly herbivorous, meaning their diet consists mainly of plants. They are likely the largest species within the iguana family. While some other lizards might match them in weight, the green iguana is a massive reptile. They are native to a wide area from southern Mexico to central Brazil, Paraguay, and Bolivia.

They are also found throughout the Caribbean in places like Aruba and Grenada. Because they are so hardy, they have become highly invasive in many tropical environments around the world.

Living on a plant-based diet requires special biological adaptations. Plants have less dense nutritional content than meat. They also contain high levels of potassium. Because of this, iguanas must eat large amounts of food to meet their metabolic needs. This diet creates a challenge for osmoregulation, which is how an animal manages its internal salt and water balance. Most animals create concentrated liquid urine to remove excess salt. However, iguanas cannot make urine more concentrated than their own bodily fluids. To solve this, they use a lateral nasal gland. This salt gland helps them expel excess potassium and sodium chlorides.

An iguana's physical features help it survive in its environment. They have a row of spines along their backs and tails for protection.

Their tails are whip-like and can deliver painful strikes. If a predator grabs an iguana by the tail, the lizard can actually allow the tail to break off to escape. It will eventually regenerate a new one. They also possess a large dewlap under the chin. This flap of skin helps regulate body temperature and is used in territorial displays.

For vision, they have excellent color sight. They even possess a parietal eye on top of their heads. This "third eye" is a photosensory organ that detects changes in light and dark. It helps them spot predators moving above them.

Green iguanas show significant geographic variation in appearance. Despite their name, they are not always green. In Peru, they may appear bluish with bold markings. In Costa Rica, some are bright red.

In Mexico, they often appear orange. On various islands, they can be lavender, black, or reddish brown. Even within a single island, populations can differ. For example, iguanas on St. Lucia have black dewlaps and white irises. This is different from the typical orange dewlap and yellow irises seen in other populations. These differences show how the species adapts to specific local environments.

Scientific study of the species began in 1758. Swedish botanist Carl Linnaeus was the first to officially describe it.

Since then, the taxonomy, or the way we classify them, has changed frequently. Scientists from El Salvador, Mexico, and the United States used DNA-sequence data to study populations from 17 countries. This research suggested the species originated in South America. It then radiated through Central America and the Caribbean. There is still debate about certain groups. Some scientists believe certain populations are distinct species, while others classify them as regional subspecies.

Reproduction in green iguanas involves specific social and biological behaviors. They are oviparous, which means the females lay eggs. A female may lay a clutch of 20 to 71 eggs once per year.

After laying the eggs, the female provides no parental protection. The eggs hatch after an incubation period of 10 to 15 weeks. Interestingly, juvenile iguanas stay in familial groups during their first year. In these groups, males have been observed using their bodies to shield females from predators. This is the only reptile species known to exhibit this specific protective behavior.

Green iguanas are highly capable in different habitats. They are agile climbers that can fall from high branches without injury. They use their hind leg claws to grasp leaves and break their fall. When swimming, they stay submerged and use powerful tail strokes to move.

They are also skilled burrowers. They can create burrows that are quite deep with a diameter of 10 centimeters. Their presence in new areas, such as the island of Anguilla in 1995, provides evidence of oceanic dispersal. This happens when animals are washed ashore by events like hurricanes, allowing them to colonize new lands.