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Texas Invasive Species Institute

Texas Invasive Species Institute

Green Iguana

Iguana iguana

Class: Reptilia
Order: Squamata
Family: Iguanidae

Iguana iguana

Photographer: Gouldingken Source: en.wikipedia.org Copyright: (CC BY-SA 3.0)


The green iguana is one of the largest lizards present in the United States. Adult males can grow up to 6 feet long and weigh as much as 17.5 pounds, but normally are 9-12 lbs. A crest of large spines along the back and tail along with a large dewlap under the chin help identify this strikingly-green species. Confusingly, the Green Iguana may be brown, gray, black or dark green. The males turn orange when they are mating. Hatchlings and juveniles are bright green, and adults have black bands on their sides and tails.

Ecological Threat

Due to the larger size, high fecundity and population numbers, Iguana iguana has become a nuisance. For Puerto Rico, the iguanas overrun the island, quickly displacing native herbivores, invading natural rainforests and destroying backyards and gardens. This is also a concern for Florida because of their strong presence in the Everglades and their ability to push out native lizards and insects. Specifically, the Miami blue butterfly (Cyclargus thomasi bethunebakeri) is not able to re-colonize in the Florida Keys because the Green Iguanas are eating all the host plants the butterflies need to lay their eggs. Also, have been observed using the burrows of the Florida Burrowing Owl, a species of special concern, all of which can make them more of a serious threat to Florida's ecosystem than originally believed. Thankfully, Green Iguanas are intolerant to cold temperatures.  Populations in Florida have been reduced from unexpected freezes, and perhaps a similar scenario occurs in South Texas.


Iguanas tend to be arboreal and prefer large trees overhanging water, into which they dive to escape predators. Green iguanas are herbivores that feed on leaves, fruits and flowers. Juveniles will eat insects in addition to plant food. Preferred plants are hibiscus, orchids, roses, garden greens, squashes and melons. They breed during the dry season and 65 days after mating females burrow up to 3 feet deep.  Over 3 days deposit 20-70 eggs in the burrow and the eggs hatch during the wet season. The juveniles become sexually mature in3 to 4 years and will live several years after maturity. They have been known to live up to 20 years.


Popular as pets, green iguanas have spread to the United States through this trade. Iguanas can grow very large and ornery, to where they bite and whip their tails at their owners. This behavior causes them to be released into the wild. They were first reported outside of captivity in Miami, Florida in 1966 and are now overrunning the Everglades. In Texas, they slowly worked their way up from Southern Mexico to Southern Texas, where they have been established at least since the 1990s. Luckily, expansion further North in Texas is unlikely due to irregular freezes, but with warmer temperature trends anything could happen. For Puerto Rico iguanas have completely overrun the island and are a major pest.

Native Origin

S. Mexico through Central America to Ecuador and Brazil

Current Location

U.S. Present: FL, HI, PR, TX and US Virgin Islands

U.S. Habitat: Canals, ditches and ponds where trees overhang the water.


The invasion of the Green Iguana to is largely due to the pet industry. Iguanas grow to very large sizes and owners quickly can’t accommodate them. It is illegal to released captured animals so before owning an iguana, weigh the pros and cons. Sometimes a 6 foot, 25 year old lizard isn’t for everyone.

Best control measures on a local level, are to discourage iguanas by removing protective cover from the yard and not planting their favorite plants. Also, wrapping tree trunks in metal prevents these arboreal lizards from climbing up them. Local iguana populations along canals and mangroves have been reduced using boats to collect those knocked off of branches when the temperatures are in the 40s.

In Florida, iguanas are protected by anti-cruelty laws. In Hawaii, strict laws regulate the importation and possession of green iguanas. Violations can lead to fines upwards of $200,000 and three years in jail.


Hollingsworth, Bradford D. 2004). The Evolution of Iguanas an Overview and a Checklist of Species, Iguanas: Biology and Conservation (University of California Press): pp. 40–41

Krysko, Kenneth L; Enge, Kevin M; Donlan, Ellen M; Seitz, Jason C 2007. Distribution, Natural History, and Impacts of the Introduced Green Iguana in Florida, Iguana: Conservation, Natural History, and Husbandry of Reptiles (International Reptile Conservation Foundation) 14(3):142–151

Woodward, Susan L., and Joyce Ann. Quinn. 2011. Green Iguana. Encyclopedia of Invasive Species: From Africanized Honey Bees to Zebra Mussels. Santa Barbara, CA: Greenwood, 221-24. Print.

Youth, Howard 2005. Florida's Creeping Crawlers, Zoogoer 20(3).

Internet References




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