Green iguanas have been documented using the burrows of Florida’s native Burrowing Owl and gopher tortoise, both of which are listed as threatened species by the state (8, 17). The presence of iguanas could potentially displace these native species from their burrows. Green iguanas will occasionally eat bird eggs (16, 17), but to date there is no scientific evidence that they have harmed bird populations in Florida. Green iguanas are primarily herbivorous and eat flowers, leaves, and fruits of ornamental plants. As a result, they could transport seeds of cultivated plants, including invasive species, into nearby natural areas and undermine efforts to control invasive plants in nature preserves (15). However, a study of green iguana movements in southeast Florida found that iguanas at two locations did not move very far, suggesting that their impacts to natural areas through seed dispersal may be minimal (20).

Gray nickerbean (Guilandina bonduc) is among the many plants that green iguanas feed on in south Florida. This species is one of two primary host plants for caterpillars of the Miami blue butterfly (Cyclargus thomasi bethunebakeri), which only occurs in Florida and is a federally listed endangered species (Figure 12). The Miami blue prefers to lay its eggs on developing shoots and flower buds of the nickerbean. This small butterfly has only been found in three places in the past 20 years—Key West National Wildlife Refuge, Great White Heron National Wildlife Refuge, and Bahia Honda State Park (21). In the early 2000s, green iguanas at Bahia Honda State Park were eating so much nickerbean that scientists concluded they were depriving the Miami blue butterflies of their food and may have been one of several potential factors that contributed to the eventual loss of the Miami blue population at Bahia Honda State Park (21, 22).

Green iguanas in Florida thrive in urban environments and are often seen basking openly in areas frequented by people. Although the iguanas are not usually aggressive towards people or pets, in some cases they can become serious hazards, as several news articles have reported. In one instance, a green iguana darted into the road, causing a bicyclist to crash. The man required stitches on his head, and the iguana did not survive the encounter (23). Green iguanas also may cause vehicle accidents when they dash across roads (14). In places in Florida with high densities of iguanas, they are often found as road-kills after being hit by cars (24). Green iguanas can become an aerial hazard during severe cold snaps in south Florida. Sustained temperatures of 30–40 degrees Fahrenheit cause green iguanas to become lethargic and stiff, and they may fall out of trees as a result. In fact, the National Weather Service in Miami declared an unofficial “falling iguana” alert in January of 2020, warning citizens to watch out for falling lizards and avoid getting too close to them on the ground in case the iguanas warmed up and acted defensively (25).

Green iguanas are also a known hazard to airplanes on the tarmac and have delayed flight departures and arrivals at the Miami International Airport because they bask on runways (14). They have also disrupted air traffic in Puerto Rico (26), and in 2011 the cost of managing iguanas (removing iguanas and their nests) at the island’s busiest airport was $98,000 (14).

In addition to being physical hazards, green iguanas in captivity are also known carriers of E. coli and Salmonella bacteria. In a study of captive green iguanas in Mexico, nearly 40% were found to carry E. colistrains that were resistant to antibiotics (27). However, there is no scientific evidence that indicates wild green iguanas in Florida transmit pathogens to humans. However, they will defecate on docks, pool decks, and patios, which is unsightly and unsanitary (15). Green iguanas are also a nuisance for homeowners and at botanical gardens because the lizards eat ornamental plants, such as orchids, hibiscus, roses, nasturtium, and caladiums (15). To protect vulnerable plants from foraging iguanas, wire mesh or electric fencing may need to be installed, and trees can be protected by wrapping them with sheet metal to exclude climbing iguanas (15).

The burrowing habits of green iguanas may damage water-containment infrastructures. Green iguanas are well known for digging burrows as hiding places, and females lay eggs in nest burrows. Iguanas may dig these burrows along the banks of canals and levees as well as at the bases of sea walls. When this occurs at locations with high densities of iguanas, there is concern that their burrows may increase erosion and compromise the integrity of the structures (17). For example, in January of 2020, the city of West Palm Beach spent almost $2 million on repairs to an aging, earthen dam, and green iguana burrows were blamed for contributing to the need for repairs

Green iguanas are not native to Florida and are considered an invasive species due to their impacts to native wildlife. Like all nonnative reptile species, green iguanas are not protected in Florida except by anti-cruelty law and can be humanely killed on private property with landowner permission. This species can be captured and humanely killed year-round and without a permit or hunting license on 32 public lands in south Florida.

Effective April 29, 2021 

Green iguanas were added to Florida’s Prohibitedspecies list.  Learn how this impacts pet owners and other entities.

DESCRIPTION

Green iguanas are large, typically green lizards, though they can sometimes be brown or almost black in color. Some adults can take on an orange or pink coloration during certain times of the year. Hatchling and young green iguanas usually have bright green coloration.

Green iguanas have a row of spikes down the center of the neck, back, and upper portion of the tail, and have dark black rings on the tail. Mature male iguanas develop heavy jowls and a throat fan (or dewlap) that are much larger than those of female iguanas. Larger throat fans can make male iguanas appear bigger, repel rivals, or warn predators. Female iguanas may choose to breed with male iguanas that have larger dewlaps. The throat fan can also help iguanas regulate body temperature.

Male green iguanas can grow to over five feet in length and weigh up to 17 pounds. Females can also reach five feet in length but usually do not exceed seven pounds. Females typically reach reproductive maturity at two to four years of age. Green iguanas typically mate in October through November in their native range, and nesting occurs on riverbanks, beaches and other sandy areas. Females dig egg chambers that may contain nearly 80 feet of interconnected tunnels and multiple entrances and lay clutches of anywhere from 14-76 eggs. Green iguanas can live up to 10 years in the wild and 19 years in captivity.

Green iguanas can live on the ground, in shrubs, or in trees in a variety of habitats including suburban developments, urban areas, small towns, and agricultural areas. They are excellent swimmers, tolerating both salt and freshwater and can submerge themselves for up to four hours at a time.

Green iguanas feed on a wide variety of vegetation, including shoots, leaves, blossoms and fruits of plants such as nickerbean, firebush, jasmine, orchids, roses, Washington fan palms, hibiscuses, garden greens, squashes and melons. Their tendency to eat ornamental plants can make them a nuisance to homeowners. Adult green iguanas can also feed on bird eggs and dead animals. Juvenile green iguanas feed on vegetation, insects and tree snails.

The native range of green iguanas extends from Central America to the tropical parts of South America and some eastern Caribbean islands.

Green iguanas were first reported in Florida in the 1960s in Hialeah, Coral Gables and Key Biscayne along Miami-Dade County’s southeastern coast. Green iguana populations now stretch along the Atlantic Coast in Broward, Martin, Miami-Dade, Monroe and Palm Beach Counties and along the Gulf Coast in Collier and Lee Counties. There have also been reports as far north as Alachua, Highlands, Hillsborough, Indian River and St. Lucie Counties. However, individuals observed in more northern counties are likely escaped or released captive animals and are unlikely to establish populations, as iguanas are not cold hardy. In cleared habitats such as canal banks and vacant lots, green iguanas reside in burrows, culverts, drainage pipes and rock or debris piles. South Florida’s extensive man-made canals serve as ideal dispersal corridors to further allow iguanas to colonize new areas.

Green iguanas cause damage to residential and commercial landscape vegetation and are often considered a nuisance by property owners. Iguanas are attracted to trees with foliage or flowers, most fruits (except citrus) and almost any vegetable. Some green iguanas cause damage to infrastructure by digging burrows that erode and collapse sidewalks, foundations, seawalls, berms and canal banks. Green iguanas may also leave droppings on docks, moored boats, seawalls, porches, decks, pool platforms and inside swimming pools. Although primarily herbivores, researchers found the remains of tree snails in the stomachs of green iguanas in Bill Baggs Cape Florida State Park, suggesting that iguanas could present a threat to native and endangered species of tree snails. In Bahia Honda State Park, green iguanas have consumed nickerbean, which is a host plant of the endangered Miami Blue butterfly. As is the case with other reptiles, green iguanas can also transmit the infectious bacterium Salmonella to humans through contact with water or surfaces contaminated by their feces.