Pets Gone Wild: Iguanas Spread Rapidly In South Florida

January 31, 2005

FORT LAUDERDALE, Fla. — Brought into Florida as pets, iguanas are a good example of how exotic animals can become a nuisance in the state, says a University of Florida pest management specialist.

Pet iguanas that have escaped or been released are now well established throughout South Florida and can be found as far north as the Tampa Bay area, said Bill Kern, an assistant professor of entomology with UF’s Institute of Food and Agricultural Sciences.

“Florida’s subtropical climate allows these large herbivorous (plant-eating) lizards to survive, reproduce and become a permanent part of the environment,” he said. “As a result, tens of thousands of iguanas are multiplying in South Florida.”

Three large members of the iguana family are common – the green iguana (Iguana iguana), the Mexican spiny-tailed iguana (Ctenosaura pectinata) and the black spiny-tailed iguana (Ctenosaura similis).

“Adult iguanas are large, powerful animals that can bite, cause severe scratch wounds with their extremely sharp claws and deliver a painful slap with their tail,” Kern said. “These reptiles usually avoid people, but will defend themselves against people and pets who try to catch or corner them.”

Wild adult iguanas, which can be dangerous, never tame sufficiently and rarely make acceptable pets, he said.

Iguanas eat valuable landscape plants, shrubs and trees as well as orchids and many other flowers. They do not eat citrus, but they like fruit such as berries, figs, mangoes, tomatoes, bananas and lychees, Kern said.

Mike Maunder, director of Fairchild Tropical Botanic Garden in Coral Gables, said hundreds of iguanas in its garden are a major problem because they feed on important plant collections.

“Iguanas will climb trees to feed, and young specimen trees have been badly damaged and in some cases killed,” he said. “Our historic hibiscus garden was grazed to the ground and has been moved to possibly a safer location. The impact of these herbivorous animals in a botanic garden cannot be sustained – five large iguanas eat as much as one sheep!”

Maunder said their plant collection will be subject to continual damage from iguanas until an effective and humane management system can be initiated.

Iguanas also dig burrows that undermine foundations and sidewalks, Kern said. Iguana burrows next to seawalls cause erosion and eventual collapse of the walls. Droppings from iguanas litter areas and may be a source of salmonella bacteria, which causes food poisoning.

Alligators, dogs, raccoons and birds of prey are probably the only natural enemies of iguanas in the suburban environments of South Florida. Automobiles and people are the main cause of mortality of adult iguanas, he said.

In tropical America, large predators such as ocelots, pumas, jaguars, anacondas and boa constrictors eat iguanas. Iguana meat is considered a delicacy by people in Central and South America.

Kern said it is illegal to release any exotic animal in Florida, including iguanas. Because they are not native to Florida, they are not protected in the state – except by anti-cruelty laws.

Green iguanas are listed by the Convention on International Trade in Endangered Species because of their economic importance and over-harvest for the pet trade. In Florida, all captured iguanas must be kept in captivity as pets or captive breeding stock, or must be destroyed. They cannot be released into the wild, he said.

Iguanas, which are considered exotic unprotected wildlife, can be captured and removed by property owners from their own property at any time without special state or federal permits, Kern said. Some counties or municipalities may have passed statutes that protect these invasive exotics, so check with local authorities before removing iguanas.

They may be caught by hand, noose pole, net or trap. Only live traps and snares are legal in Florida. Babies can be sold or given to pet stores or exotic pet wholesalers.

“When temperatures drop below 50 degrees Fahrenheit, cold-stunned iguanas can sometimes be simply picked from branches or picked up off the ground after they fall from trees,” he said.

Kern, a vertebrate pest management expert at UF’s Fort Lauderdale Research and Education Center, said male iguanas are territorial against other males, but are not territorial against females and juveniles.

“These large lizards like to bask in the sun on sidewalks, docks, seawalls, landscape timbers and open mowed areas,” he said. “If frightened, green iguanas and basilisks dive into water, making them very difficult to capture. Spiny-tailed iguanas usually retreat into their burrows.”

While adult iguanas prefer feeding on foliage, flowers and fruit, they will occasionally eat animal material such as insects, lizards and other small animals, nestling birds and eggs. Juveniles eat more insects, and hatchling green iguanas eat the droppings of adult iguanas to acquire the gut bacteria they need to digest plant material, Kern said.

“Don’t feed iguanas in your yard because it will attract more iguanas and create problems for you and your neighbors,” Kern said. “Pans of cut fruit will attract rats and raccoons as well as iguanas.”

In addition, there are other large lizards established in Florida that some people mistake for iguanas, he said. The brown basilisk (Basiliscus vittatus) is a large lizard – up to two feet in length – that occurs in the same areas as introduced iguanas. Knight anoles (Anolis equestris) commonly reach between 12 to 18 inches. Nile monitor lizards (Varanus niloticus) are carnivorous and eat small birds and mammals.