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Taxonomic Background
Green Iguanas are reptiles, and like all reptiles, they belong in the animal kingdom (Animalia). Within the animal kingdom, there are a large number of different animal groups known as phyla (singular: phylum). All vertebrate animals, that is, all animals having a backbone, belong in the phylum Chordata. Because reptiles are vertebrates, they are chordates. Phyla are also divided up into many smaller groups, called classes. All reptiles (snakes, lizards, crocodilians, turtles and tuataras) belong in the class Reptila. Within class Reptila exist smaller groups called orders. Lizards and snakes belong in the order Squamata. Within this order are two main suborders: Serpentes, which includes the snakes, and Sauria, which includes the lizards. Iguanas, of course, belong in suborder Sauria. Within Sauria are several families, including the family Iguanidae, in which green iguanas belong. The taxonomy can be summed up in a glance like this:

Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Sauria
Family: Iguanidae

* The family of Iguanidae includes all lizards commonly called “iguanas”. There are eight groups called genera (singular: genus) within the family of Iguanidae. Here is a short description of the green iguana’s closest relatives:
    Genus Cyclura – These lizards are commonly called rock iguanas. They are found in the Caribbean islands. They are highly endangered, and those that are sold in the pet trade are captive bred.
    Genus Amblyrhyncus – Members of this genus are known as the Galápagos marine iguanas. As fascinating as these guys are, they are not kept in captivity, because they feed on marine algae – a diet almost impossible to provide!
    Genus Conolophus – These lizards are close cousins to the marine iguanas, and are called the Galápagos land iguanas. They feed on plants, including cacti.
    Genus Ctenosauria – These guys are commonly called spiny tailed iguanas.
    Genus Dipsosaurus – This genus includes the desert iguanas of the Southwestern United States and Mexico.
    Genus Sauromalus – The chuckwalla, which is found in the SW United States, Mexico and on islands in the Gulf of California, belongs in this genus.
    Genus Brachylophus – Commonly known as the Fijian banded iguana, this lizard is native to the islands of Fiji and Tonga.
Green iguanas belong in the Genus Iguana, which includes two species: Iguana delicatissima, which is found in the Lesser Antilles islands, and Iguana iguana – the green iguana.

Natural History

Where Do Green Iguanas Live? Wild green iguanas are found naturally in southern Mexico, Central America, and most of South America. A few are found on the Lesser Antilles islands, along with I. delicatissima.

Feral populations can be found in parts of California, Florida and Hawaii. These populations consist of individuals that either escaped from captivity or were purposefully released by their owners, and which have survived and even thrived and bred in this new habitat. Although many people may think that such populations of non-native species add to the variety of the environment, they are, in fact, quite harmful to native species. They disrupt the ecosystem, compete with native species for resources, and prey on species that are not adapted to deal with such predators. Iguanas that are introduced to new areas are no different. In fact, it is illegal to own pet iguanas in the state of Hawaii, because the isolated island ecosystems are so easily disrupted by the introduction on exotic, or non-native species. Despite this, feral populations of iguanas do exist there. Populations of feral iguanas in Florida cause much damage and frustration each year. Owners of pet iguanas must be responsible for their pets, and make a conscious effort to prevent them from entering the wild in areas where they are not native.

In their native habitats, green iguanas are found mostly in the rainforests, although some do live in drier, costal areas. They tend to limit themselves to lower altitudinal regions, where temperatures are warm enough for their ectothermic lifesyle. The photo below of a wild baby iguana was taken in Mexico.

How Do Green Iguanas Live? Green iguanas are generally arboreal, meaning that they live in trees. Their long claws are superb adaptations for this lifestyle. Although they may appear to be quite clumsy as they tip over your furniture, knock things off shelves and fall off of perches, they are quite good climbers. They spend the majority of the day high in the forest canopy, and venture to the ground only to move from tree to tree, to mate, and to lay eggs. They are also good swimmers and jumpers.

The coloring and body shape of green iguanas varies a bit from region to region. For example, the iguana in the photo below is from the island of St. Thomas. Its grey coloring is typical for the population of I. iguana there. These iguanas are commonly found hanging out on rocks along the island shore.

Green iguanas tend to be cryptically colored. This means that they are well camouflaged, and blend in nicely with their surroundings. This helps protect them from predators. This is especially important for hatchlings and juveniles, which are low on the food chain and must be very wary of predators attacking from the air and the ground. The wild baby iguana in the photo below, from Ecuador, was hiding in a plant.

Some green iguanas have small “horns” on their snouts. It was once thought that such iguanas belonged to a separate subspecies of Iguana iguana, but this is no longer the case. Some pet stores still market such horned iguanas as a separate species, and sometimes they charge more money for these individuals by convincing uninformed customers that such iguanas are a special, rarer breed. In fact, iguanas native to the same general area may or may not have these horns. It does not seem to be a trait that is regional in any way. It is simply an example of genetic variety within the species.

The Typical Iguana Day - Green iguanas are very diurnal. This means that they are active during the day and sleep at night. My experience with my own iguanas demonstrates how rigidly they adhere to this activity cycle. Unlike cats and dogs, which tend to nap on and off during the day and are likely to be up and active when their owners are awake, iguanas wake up in the morning, stay awake the whole day, go to bed in the evening and sleep the whole night through. My iguanas get visibly sleepy at about 7:00 PM in the fall/winter months (when it starts getting dark outside) and are zonked out cold by 8:30 PM, whether their cage lights are still on or not. If I wake them up too early in the morning, they act just like people – giving me a weary, half-awake look. It takes them a while to really wake up. This is why it is important to provide your iguana with a routine day/night schedule and a quiet, dark place away from household activity to sleep at night.

In the wild, iguanas wake up when the sun comes up, move to an area in the sun to bask and warm up enough to get going, and then begin to forage for food in the mid-late morning. They feed on a variety of leaves, flowers, soft fruits and young plant shoots. They are strict herbivores. After eating, they will find a warm, sunny place to bask while their food digests. Then, in the evening, they will find a safe place to settle down and spend the night. It sounds like quite the relaxing life, doesn’t it?

The Iguana’s Place in the Environment - Green iguanas are an essential part of their native habitat, as are all organisms. As juveniles, they make a tasty meal for many predators. As adults, their fruit-feeding activities may help spread seeds in the habitat. Adult iguanas are not at risk from many predators, as they can defend themselves with sharp teeth and strong tails. If they make it to adulthood, they can be expected to live for 10-15+ years. There is one predator that the iguana is no match for, however – humans.

Native people often refer to green iguanas as “the chicken of the trees”, or “bamboo chicken”. Green iguanas are harvested for their skin, meat and eggs. The time of year for iguana mating season varies from region to region, but it tends to fall in the months of January and February. Wild, gravid females are captured and their eggs are collected for food and to supply “iguana farms” with babies for the pet trade. While small-scale hunting is not a threat to iguana populations, large-scale harvesting, particularly to supply the pet trade, is.

Although large-scale hunting and egg-collecting activities threaten wild iguana populations, the biggest threat to the wild existence of these lizards is habitat loss. As the rain forests disappear, so to do green iguanas. Although they are not currently listed as threatened or endangered, they are certainly at risk, along with all the other inhabitants of these forests.

Happily, sometimes wild iguanas can benefit from and enjoy the company of people. The photo below was taken in a park in Ecuador. These wild iguanas are accustomed to being fed by people in the park.

Marine Iguanas and Land Iguanas
Marine Iguanas by Robert Rothman
Land Iguanas by Robert Rothman
Univeristy of MI Museum of Zoology page on Marine Iguanas
Univeristy of MI Museum of Zoology page on Land Iguanas

Melissa Kaplan's page on Cyclura
Univeristy of MI Museum of Zoology page on Cyclura
The Blue Iguana Recovery Program

The iguana in the photo below is a wild adult Grand Caymen Blue Iguana - a critically endangered species.

Chuckwalla and Desert Iguana
Melissa Kaplan's page of Chuckwallas and Desert Iguanas
San Diego Natural History Museum's page on Desert Iguanas
San Diego Natural History Museum's page on Chuckwallas

Fiji Iguanas
Fiji Crested Iguana
International Conservation Fund for the Fiji Crested Iguana
Virtual Museum of Natural History page on the Fiji Banded Iguana
B.J. Herp Supplies - Fiji Banded Iguana

Spiny-tailed Iguana
Melissa Kaplan's page on the Spiny Tailed Iguana
Ribbit Photography page on Spiny-tailed Iguanas

I.delicatissima - Lesser Antillean Iguana
Information about the Lesser Antillean Iguana conservation stamp
The Iguana Specialist Group - I. delicatissima

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