Although it looks like a small, fierce dinosaur with its claws and spines, this shy creature's main pleasure is lounging in the treetops nibbling on tender shoots and leaves. The green iguana, which is the largest lizard in the Americas, may weigh up to 30 pounds (13.6 kilograms) and reach a length of 6 feet (1.8 meters). Its whip-like tail makes up almost two thirds of its length. The green-scaled body has a crest of soft spines running along the middle of the back. Hanging on the throat is a fold of loose skin called a dewlap.
Green iguanas can be found basking in the sun of tropical and subtropical forests from Mexico to Brazil. They belong to the group of reptiles, called Squamata, that includes all lizards and snakes. Its large family includes horned and spiny lizards, chuckwallas, anoles, and basilisks. While most of its relatives live in the Americas, some live as far away as Madagascar and Fiji.
Iguanas and Their Young. Green iguanas court and breed in January or February. When an iguana mates or is being aggressive, parts of its body, such as the head and shoulders, change color. From its greenish color, the iguana changes to orange or pink.
About two months after breeding, the female digs a tunnel in soft ground and lays 20 to 90 round, white-shelled eggs in a chamber at the tunnel's end. Each egg is about 1 inch (2.5 centimeters) in diameter.
If the nest is not disturbed, the eggs hatch about five months after they are laid. The baby iguanas are about 10 inches (25 centimeters) long. Often, they leave the nest hole together and stay in groups. They clean one another, rub chins, and sleep together.
The young animals are bright green. As they get older, dark bands of scales begin to develop across the shoulders and tail. The iguanas grow rapidly. By the time iguanas are a year old, they are about 3 feet (about 1 meter) long. Although iguanas can live up to ten years, most are killed by predators before their second birthday.
The Life of an Iguana. Iguanas, like all reptiles, are cold-blooded: Their blood is the same temperature as the outside environment. They still need heat for their bodies to function normally, so much of their time is spent soaking up heat energy from the sun. During cold weather, the animals move to the forest floor and seek warm places under logs or in holes.
Each male iguana marks out its own territory. It produces a waxy, scented substance and leaves traces of it among the leaves and branches of its treetop home. It defends this territory against other male iguanas. Rising up on its front legs, it snaps its tail and hisses to scare off an intruding iguana. The best fighter has the largest territory — and mates with the most females.
The Iguana and Its Environment. At one time the iguana flourished in the lowland forest, but much of the forestland has been cleared to raise crops and cattle. Animals and people eagerly hunt the iguana, killing almost 95 percent of the iguana population for food. Iguana meat is considered such a tasty treat that it is often called "chicken of the trees." The fat of the iguana is also used as a salve for burns.
Today, efforts are being made to establish iguana ranches in tropical forests. The successful breeding of captive iguanas will not only help save the threatened iguana, but it will also save the vanishing tropical forests.