Are Iguanas Invasive in Florida? Green Iguanas Explained

How did iguanas get to Florida?

The green iguana is native to Mexico, Central and South America and many Caribbean islands, but not to Florida. According to the Florida Fish and Wildlife Conservation Commission (FWC), green iguanas have been reported in South Florida since the 1960s.

Two routes brought them. Some of the first animals in the Florida Keys were probably stowaways on ships carrying fruit and other cargo from the tropics. Far more arrived through the pet trade. In the 1990s the United States imported hundreds of thousands of young iguanas a year, many bred on farms in Central and South America. Iguanas can grow to over 1.5 m (5 ft) and live for decades in captivity, and some owners released animals they could no longer keep, while others escaped.

Hurricanes and the rafting of floating vegetation have also moved iguanas between Caribbean islands, so once a population is established, it can spread on its own. In Florida the main spread has followed canals, coastlines and suburbs.

Where do iguanas live in Florida?

Green iguanas are most common in Miami-Dade, Broward and Palm Beach counties and throughout the Florida Keys. They are also established along the Gulf Coast in counties such as Collier and Lee, and individuals turn up farther north from time to time.

They favor places that resemble their native riverside forests: trees and shrubs next to canals, lakes, ponds and the sea. Golf courses, parks, gardens, marinas and waterfront homes all suit them. They bask on seawalls, docks and branches and often drop into the water when disturbed.

Cold limits how far north they can spread. Iguanas are tropical reptiles that cannot produce their own body heat, so freezing or near-freezing nights can slow, stun or kill them. This is why the population is concentrated in the mildest part of the state.

Why are iguanas considered invasive?

An invasive species is a non-native organism that establishes itself in the wild and causes harm to the environment, the economy or human health. Green iguanas meet all three parts of that definition in Florida.

Damage to plants and native wildlife

Iguanas are plant-eaters, and in Florida they eat many ornamental plants, fruit, flowers and vegetables in gardens and nurseries. More worrying for conservation, they have been recorded feeding on native plants of concern. These include the endangered Florida native shrub Cordia globosa and nickerbean (Caesalpinia) plants, which are a food plant for caterpillars of the endangered Miami blue butterfly.

They also compete with native animals for space. On Marco Island, green iguanas have been seen using the burrows of the Florida burrowing owl, a species of special concern in the state. Elsewhere they occupy burrows made by gopher tortoises.

Burrows that undermine seawalls and banks

Female iguanas dig nest burrows that can be more than 1 m (3.3 ft) deep, and adults dig shelters too. Burrows in canal banks, levees, dikes, sidewalks and the soil behind seawalls can cause erosion and lead to collapse, an expensive problem in waterfront communities.

Health and nuisance concerns

Like many reptiles, iguanas can carry Salmonella bacteria in their gut. Their droppings on docks, pool decks and patios are a common complaint. Iguanas sometimes climb onto power lines and equipment as well.

How many iguanas are in Florida?

Nobody knows the exact number, and populations rise and fall with the weather. After a run of mild winters, iguanas can become extremely common in parts of the Miami area and the Keys. A severe cold snap can kill or stun large numbers, as happened in 2010, but the population has always recovered.

Their high breeding rate makes this recovery possible. A female can lay a clutch of a few dozen eggs every year, and with few natural predators in suburban Florida, many young survive.

How does Florida treat green iguanas?

The FWC treats green iguanas as a harmful nonnative species. They are not protected in Florida except by the state’s anti-cruelty law. In 2021 the state added green iguanas to its list of prohibited nonnative species, which strictly limits keeping, breeding and selling them and is meant to stop new animals from being released into the wild.

The FWC also asks people never to release unwanted pets. Florida’s Exotic Pet Amnesty Program lets owners of nonnative pets surrender them without penalty, so they do not end up in the wild.

Other invasive reptiles in Florida

Florida has more established nonnative reptiles than almost anywhere else in the world. Besides green iguanas, the state is home to introduced black spiny-tailed iguanas, Argentine tegus, brown anoles, several gecko species and the Burmese python, which has spread through the Everglades. To see how pythons arrived and what they changed, read How did pythons get to Florida?.

Puerto Rico has an even larger green iguana problem. In 2012 officials there estimated the island’s population at around 4 million animals. Hawaii, the U.S. Virgin Islands and the Rio Grande Valley of Texas also have introduced populations.