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Iguana Invasion

Exotic Pets Gone Wild in Florida

and what to do about them

Common Green Iguana

Iguanas and Lizards

Iguanas are Lizards

Iguanas are large lizards that look like miniature dinosaurs. They can be green, orange, black, brown, blue, and other colors. There are 350 species of iguanas living around the world today. Only 3 of these species are living and breeding here in Florida:
  • Common Green Iguana
  • Mexican Spinytail Iguana
  • Black Spinytail Iguana
The 3 species found in the wild in Florida were imported as pets from South America and Central America, where they live mostly along the coastlines or on islands close to the mainland. Iguanas are also sold by breeders in the U.S.

Lizards are reptiles. Like snakes, iguanas have scales, lay eggs, and are cold-blooded. So iguanas shed their skin, lay their eggs in large nests, and bask in the sun to boost their body temperature. Iguanas require year-round warm weather to survive in the wild. If the temperature drops below 40 degrees, iguanas become sluggish. Their metabolism slows and their skin turns dark from the stress. Too many cold days in a row and they will die.

Iguanas dig holes in which they lay one to six dozen eggs. Animals that eat the eggs include crows and snakes. Iguana babies are only seven inches long. The babies are eaten by a variety of predators. Herons, owls and other birds prey on them. So do raccoons, opossums, and rats. Dogs and cats will chase little iguanas and sometimes kill them. Once the babies are full grown, however, they may be four to seven feet in length. There are no native predators in Florida to bother adult iguanas--except for us.

Common Green Iguanas

Despite its name, the Green Iguana may be brown, gray, black or dark green. The males turn orange when they are mating. Babies and juveniles are bright green, and adults have black bands on their sides and tails.

Green Iguanas have a dorsal crest and a large rounded scale on each jowl. The crest is larger on the males. They have a baggy dewlap hanging from the neck which they wag when mating or defending their territory. Their tails are long.

The Common Green Iguana lives in trees, usually near water. You can spot them on the branches that hang above a pond, lake, canal or river. They will sun themselves on grassy slopes, tree trunks and limbs. They are excellent climbers and swimmers. They build burrows which can weaken waterside structures like embankments, cement seawalls and docks.
Juvenile Green Iguana

Green Iguanas are herbivores and live on vegetation. They like to eat brightly colored flowers like hibiscus, orchids, and bougainvillea. Their poop is generous and they leave it on our pool decks, docks, sidewalks, and rooftops. Because they eat our plantings and poop in our yards, South Florida neighborhoods are waging war with the Green Iguana.

If you leave iguanas alone, they will not approach you or threaten you or your pets. However, if you corner them, they may bite, scratch, or whip you with their tail in self-defense. Both males and females are territorial and will defend the trees they live in and the area around them--including your entire backyard. If you dispose of an iguana in your backyard, another will come to take its place. If you prefer not to share your yard with iguanas, it is best to iguana-proof your home rather than trying to kill off the animals one at a time.

Until the abnormally cold month of January 2010, the population of Green Iguanas was exploding across South Florida. Wildlife experts estimated that hundreds of thousands of these reptiles were living south of Lake Okeechobee. This was due to a combination of newly released pets with a life expectancy of up to 20 years, multiple breeding periods with nests of up to 50 eggs, and years of extra mild winters south of Orlando. The recent record-breaking stretch of cold weather, however, has reduced the Green Iguana population significantly.

During abnormally cold weather, iguanas are known to modify their behavior. They will burrow underground or hide in caverns and hollows in the heat reservoirs found there. They may enter a state of partial hibernation zoologists call ďbrumation,Ē sleeping for the duration of the cold weather to conserve energy and body fluids. During this state, iguanas will appear rigid, their skin color darkened in a natural attempt to increase heat absorption. If disturbed, the reptile will not rouse. Their skin will feel cold to the touch and they will be unresponsive to pain. It can be difficult to determine if they are dead or alive!

Periods of hibernation are not normal for neo-tropical and tropical animals. If hypothermia sets in, iguanas usually die. Of those that survive, recovery may be slow and some will fall ill due to reduced immunity and organ failure. The iguanas that do make it will return to breeding soon enough, repopulating those areas suddenly devoid of exotic invaders. In time, the Green Iguana population in South Florida will be booming again.

Mexican Spinytail Iguana

These iguanas were brought to Florida as pets from their native habitat in the western and southern areas of Mexico. Pet owners let them loose in the Miami suburbs and they have reproduced steadily.

The male Mexican Spinytail is mostly black with white and yellowish blotches. Breeding causes an orange coloration. Females have a green tint. Babies are bright green with black markings. Adults have a black head and the tail is spiked with spines, which are actually scales. Mexican Spinytails can grow up to four feet in length.
Mexican Spinytail Iguana

The Mexican Spinytail looks a lot like the Black Spinytail Iguana. Wildlife specialists can tell them apart by the markings on their tails. Most of the Mexican Spinytails loose in Florida live in the Miami area and in the Everglades National Park, while the Black Spinytails are populating some islands off the southwest coast of the state.

Wary and alert, the Mexican Spinytail is not a common sight in the wild. They are secretive, shy, and hide in burrows they dig under sidewalks, cement seawalls, or rock piles. As babies they have many predators, but as adults they do not. They are unfriendly and will bite. This may explain why they do not make good pets.

Black Spinytail Iguana

Despite the name, the Black Spinytail Iguana is not always black. They can be brown, tan, yellow-gray or blue-gray in color. When breeding, the males are orange. Babies are bright green and juveniles have a green tint until adulthood. Adults have spiky tails. They usually grow no longer than three feet.

Native to southern Mexico and Central America, the Black Spinytail Iguana was brought to this country as a pet. In southwest Florida, some unwanted pets were released into the wild. Since the female can lay a dozen or more eggs in each breeding period, over time this species of iguana evolved into an invasive pest of concern.
Black Spinytail Iguana

An unfriendly animal, the Black Spinytail will scratch or bite if trapped. They live in burrows under the concrete foundations of homes and seawalls, which can be problematic. They also burrow into sand dunes, contributing to the erosion of beaches. Carnivores, they will eat other lizards, sea turtle eggs and hatchlings, bird eggs and nestlings. They also take over the burrows of other animals including Gopher Tortoises. The Black Spinytail will hunt through your garbage cans for food, then hiss at you if you attempt to stop them.

On islands off the west coast of Florida, the Black Spinytail population has exploded over the past 10 years. A few pets were released on Gasparilla Island in the 1970s, for example, and now there are thousands of Black Spinytails living there. Residents complain that the iguanas ruin the landscaping, spark power outages, dig up seawalls, nest in attics and appear inside homes. Environmentalists are concerned because the iguanas are competing with the native animals for food and territory, and weakening the sand dunes required for hurricane protection. And there is iguana guano everywhere, which is not good for the tourist industry.

These iguanas have been sighted on neighboring islands and the mainland. The local government has teamed up with state university biologists and wildlife trappers to address the problem. So far, the issue has not been resolved.

What to Do

You donít have to be scared of iguanas if they move into your neighborhood. They wonít attack you if you donít bother them. If you are having problems with hostile or burrowing iguanas, you might contact a wildlife trapper in your area. Remember, once you remove an iguana from your yard, another will probably take its place.

If you live in central or northern Florida in an area where feral iguanas are still uncommon, you can report exotic iguana sightings to the U.S. Fish and Wildlife Service on their Nuisance Species Hotline. This federal organization is keeping track of the breeding habits and territories of exotic species in Florida and around the U.S.

However, if you live in the South Florida area where the Common Green Iguana is as plentiful as the snowbird, local wildlife trappers will not be able to resolve what has become an insurmountable problem. You may choose to hire a trapper to remove the iguanas from your property, but the solution will only be temporary.

Wherever you live, you can iguana-proof your home. Here are the simple steps you can take in order to keep iguanas out of your yard and away from your house:
  • remove colorful flowering plants from your yard (e.g., hibiscus, impatiens, and orchids)
  • remove fruit trees from your yard (except citrus, which they wonít eat)
  • do not plant a vegetable garden in your yard
  • cut back tree canopy
  • keep trees thinned out
  • keep your entire yard free of brush and debris, landscape timber and rock piles
  • trim tree branches away from your roof and the sides of your house
  • trim tree branches so they donít hang over your dock and pool
  • attach sheet metal guards to tree trunks (to keep iguanas from climbing)
  • tie plastic bottles on your boat line (so the iguanas canít use it to climb onto your boat)
  • install a childproof fence around your swimming pool
  • install electric fencing around seawalls and docks
  • spray garlic oil (they donít like the scent)
  • spray neem oil (they donít like this bitter Indian tree seed oil )
  • let your dog roam the yard to scare off wildlife
  • spray them with a garden hose until they leave (and maybe decide to live elsewhere)
Orchid image.

Orchid image.

Sometimes a tall fence or screening around a property will discourage iguanas. But if you live on a body of fresh water in South Florida, you should expect to see these exotic animals--if you have not already made their acquaintance.

Going to war with these animals is pointless, dangerous, and inhumane. It is unwise to attempt to shoot, burn, poison, freeze, or drown an iguana, all inhumane acts. You might hurt others unintentionally, or annoy an iguana into attacking you or or your family. Even exotic animals are protected by anticruelty laws in the state of Florida. In some Florida neighborhoods, the iguana issue has caused disagreements between neighbors and police have been summoned. Shooting firearms and pellet guns is illegal within city limits. Authorities frown on inhumane treatment of animals, including exotics that some see as pests and others as vulnerable visitors in need of our protection. It is not the animalsí fault that they are imported as pets and then dumped in suburban yards when they behave naturally, like the wild animals they are meant to be.

If you want to protest the ongoing sales of iguanas and other problematic species in the state of Florida, register your opinion with the Florida Fish and Wildlife Conservation Commission.

Other Lizards on the Loose

In the state of Florida, there are more than 30 exotic lizard species living and breeding in the wild. Most of these are geckos and anoles, the small lizards you can see running across sidewalks and up the walls of buildings. Most of these species are expanding their populations, and most can be found in the urban areas of South Florida. Some were brought here by the pet trade, others arrived hidden in cargo on boats from other countries.

Most of the exotic lizard species on the loose in Florida are small, usually measured in inches. Unlike the iguanas, they are not regarded as invasive and problematic by the general public. However, biologists warn that the presence of so many non-native lizard species is significantly reducing the populations of our native lizards. For example, the exotic Brown Anole is now more abundant than the native Green Anole.

Since they are so widespread, it would be impossible to remove all the exotic lizards living in our state. Fortunately, most of these species are harmless. However, several species of non-native lizards found in Florida are of concern for safety reasons:
  • Tokay Gecko
  • Knight Anole
  • Nile Monitor

The Biting Gecko

Unlike the little brown geckos you see crawling up your walls and across your ceiling, Tokay Geckos are brightly colored and fierce. Originally imported from Southeast Asia by the pet trade, these feisty lizards have adapted to living in the wild in Florida, Texas and Hawaii, where they make their homes in trees and dine on local lizards, frogs, and insects.

The Tokay Gecko is unmistakable. Adults are 12 inches long with blue-gray coloring, spotted with bright red-orange dots. A nocturnal animal, the males make a loud call at night that sounds like to-kay.

Tokay Gecko
         Photo courtesy of Adam G. Stern
This lizard will bite and not let go. If one grabs onto your hand, you may have to dunk it underwater to make the lizard stop biting you. This may be why pet owners have dumped these lizards into parks and suburban neighborhoods around the state. These geckos are known to be breeding in a number of counties, especially along the southwest coast.

If you see one of these lizards in the wild, do not try to capture it. The bite can be painful. Unless you live in an area where these lizards are plentiful, you might report your sighting to the U.S. Fish and Wildlife Service on their Nuisance Hotline. The government is tracking the spread of exotic species throughout the country.

The Biting Anole

The Cuban Knight Anole is often confused with the juvenile Common Green Iguana because they are the same shade of green. However, on close inspection, these lizards are quite dissimilar. The Knight Anole has a triangular head, and the tail is extra long. There are yellow slash markings on the body and the dewlap is pale pink. Adults do not grow any larger than 18 inches.

In Miami, the Knight Anole is called iguanito, or little iguana. Most of the Knight Anoles living and breeding in the wild are in the Miami area, but they have been reported around the state and as far south as Key West. They were imported by the pet trade, but these lizards do not make good pets.

Knight Anoles are carnivores. They eat mostly large insects and fruit, but will prey on frogs, small anoles and geckos, small birds, bird eggs and hatchlings. When cornered, these lizards stand their ground, inflicting a heartfelt bite in order to protect themselves. They have sharp teeth.
Knight Anole

It is not easy to spot a Knight Anole because they live high up in the tops of trees, hidden in leafy canopy. You may see them sunning on tree trunks, clinging to the bark while facing the ground, or sneaking across phone lines from tree top to tree top. If you see one, do not approach or attempt to capture this lizard. Outside of the Miami area, you can report your sighting to the U.S. Fish and Wildlife Service on their Nuisance Species Hotline.

Many Knight Anoles died during an atypical stretch of cold weather in January 2010. They dropped out of trees in a frozen state similar to that experienced by Green Iguanas. Florida residents unfamiliar with these shy reptiles mistakenly identified the blackened lizards as iguanas. The overall impact of the abnormal weather on the Knight Anole population in South Florida is unknown.

The Jesus Lizard

Brown Basilisk
Native to MexIco, Belize, Panama, Costa Rica, and northern South America, the 2-foot long Brown Basilisk is olive brown and sports a crest or hood on the head. Unfriendly and skittish, these lizards will flee from humans. They can run swiftly on their hind legs, climb trees, and swim rapidly to escape perceived threats. Specially webbed toes allow basilisks to run across still water, lending the lizard a certain religious aura.

Alert and agile, the Brown Basilisk is omnivorous and eats a lot of insects. Females lay 3 to 12 eggs in the summer, usually in a hole in a canal bank. Arboreal in nature, the basilisk lives in low trees and spends time on the ground. Camouflage coloring and native shyness make these lizards difficult to spot.

Known to be breeding in Florida since the 1970s, Brown Basilisks live in Miami Dade county. Breeding populations exist in Palm Beach County as well as on the west coast of Florida.

Giant African Lizards

There are more than 30 species of Monitor lizards living around the world, including the 10-foot-long Komodo Dragon of Indonesia. The largest lizard living on the African continent, Nile Monitors may grow to 7 feet in length. The Nile Monitor is the largest lizard living and breeding in the U.S., and it is only found in the wild here in Florida.

The carnivorous Nile Monitor eats crabs and other seafood, frogs and lizards, turtles, snakes, birds, eggs, and small mammals. They will eat from garbage cans, and are known to eat house cats. They are gray or brown with dark bands and gold bands. They have a long tongue that is forked like a snakeís. Nile Monitors warn off predators by hissing and flicking their split tongue.
Nile Monitor
Photo courtesy of Adam G. Stern

Nile Monitors have been living in the wild in Florida since the early 1990s. These giant lizards are escaped pets and their offspring. They like to live near water, in Florida marshes and swamps or on the banks of rivers, lakes and canals. They dig burrows or steal them from other animals. The female lays up to 60 eggs in these burrows.

Not surprisingly, the Nile Monitor is regarded as an invasive species by the state of Florida. They are a threat to the native species we are trying to protect like the Burrowing Owl, Gopher Tortoise, and sea turtles. Nile Monitors dig up the eggs of our native alligators and crocodiles. And they freak out the humans who are coming across them in increasing numbers.

In southwest Florida, a breeding population of these large lizards has become a serious problem for the residents of Cape Coral. Hundreds of Nile Monitors travel around the city through the many man-made canals. Strong swimmers, fast runners, and good climbers, the Nile Monitors are all over the yards and roofs, gardens and parks of the city. The lizards have been reported on neighboring islands, and in other areas of the mainland. Scientists from the University of Florida are attempting to come up with a solution for the invasion before the species spreads itself around the state.

Monitor lizards are not good pets. They are nervous, bite easily, and require plenty of room to move around. This may be why so many of these huge lizards have been ďliberatedĒ into the Florida landscape. If you spot one, call a wildlife trapper in your area.

Make sure your family and pets stay away from Nile Monitors on the loose. Never approach these aggressive lizards on your own.

New Fads Mean New Invasives

The South American Tegu is a four foot long lizard with sharp teeth and claws and a forked tongue. Various species of these large lizards are popular with the pet industry right now. The babies are six to eight inches long and colorful. Buyers are unaware of what life with an adult tegu will be like. Unruly and sometimes aggressive, these reptiles are not always the best pets. Their care is expensive, they grow rapidly and may bite.

Black and White Tegu
A tropical animal, the tegu will not survive in the wild if the weather is cold. Tegus have been spotted on the loose in South Florida. Tegus have been reported living in the Everglades. It is not yet known whether they are breeding here. It is likely they will be able to adapt to our winterless environment, reproducing and spreading around the southern part of the state before scientists and the government can halt an invasion. In fact, the smart money is on the tegus. If you see a big red or black and white striped lizard, call in a local wildlife trapper. It is best not to approach these lizards because they are fast runners, good climbers, excellent swimmers--and they can inflict a powerful bite.

It is abusive to purchase a large lizard and keep it in a small cage. It is unfair to the animal to lock it in a bathroom when it becomes too big for your home. It is against the law to release an unwanted exotic pet in your local park or in an undeveloped area of town.

If you want to own an exotic reptile as a pet do the research first. Find out how big the animal gets, what kind of habits it will have as an adult, how many years it may live, and if it is dangerous or aggressive. Think of the animalís needs. Does the exotic lizard you think looks so cool really want to live in a cage in your bedroom for the rest of its life? Are you willing to take on the years of expense and responsibility that ownership of exotic reptiles entails?

Since the 1970s, Florida has maintained licensing laws for the ownership of large, potentially dangerous, exotic animals. More recently, The Florida Fish and Wildlife Conservation Commission enacted new regulations for the ownership of certain exotic reptiles. Owners of Nile Monitors (as well as pythons and anacondas) must file for special permits. Microchips implanted in the registered animals help identify owners if the pets are ever found loose.

If youíve made a mistake and are no longer able to care for your exotic lizard, do not let it loose. Check out the details about Exotic Pet Amnesty Days hosted by the Florida Fish and Wildlife Conservation Commission: www.myfwc.com. Or bring the animal back to the pet store where you purchased it. Find a home for your pet. Do not turn your pet fad into yet another exotic pet invasion.

Next time your children ask for a new and exciting pet, you can buy them a book instead. Iguana Invasion! Exotic Pets Gone Wild in Florida explains in simple words and photos what your children need to learn about the consequences of exotic pet ownership in our state. The book also serves as an excellent reference for identifying the most common non-native species.

You can protest the ongoing sales of exotic lizards and other problematic species in the state of Florida by sharing your opinion with the Florida Fish and Wildlife Conservation Commission.

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New book:

Iguana Invasion! Exotic Pets Gone Wild in Florida

by Virginia Aronson and Allyn Szejko

Available at your local bookseller, Amazon.com, Barnes&Noble.com, and Pineapple Press.

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