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Iguana Invasion

Exotic Pets Gone Wild in Florida

and what to do about them

Squirrel Monkey
Squirrel Monkey

Blog (2010)

January 31, 2010: Exotic Asian Carp causing problems around the US*

In 2006, the US Fish and Wildlife Service announced a Management and Control Plan for Asian Carp invading the US. So far, the Plan has not worked. An electrical barrier has not prevented the huge, ravenous fish from entering the Great Lakes from the Mississippi River, which is infested with the foreign species. The state of Michigan is demanding that shipping locks between the river and the lakes be closed. This year, the Supreme Court will address the issue as it involves state’s rights regarding exotic fish-infested waters.

Carp are freshwater fish commonly found in rivers and streams throughout Asia. Goldfish, a popular aquarium fish, is one species of carp. Goldfish and other carp species, imported to the US by the aquaculture industry, escape or are dumped into rivers and lakes where they begin reproducing. Some carp species have been introduced into bodies of water by wildlife agencies for biological control purposes, usually in order to help with invasive plants. Carp have also escaped from university and state research facilities.

There are seven species of Asian Carp that have been invading US waterways since the 1960s. Four of these species are regarded as nuisance species and are currently reproducing in major US rivers and tributaries: Bighead Carp, Black Carp, Grass Carp, and Silver Carp. Both Bighead Carp and Grass Carp can be found in Florida waters.

The Asian Carp is a nuisance for the same reason most exotic species are problematic: invaders compete with native wildlife for food. Carp can grow to more than 4 feet in length and weigh as much as 100 pounds. If the carp are eating, there isn’t much left over for the native fish. The threat to biodiversity, and to the fishing industry dependent on it in states like Michigan, is massive. The US Environmental Protection Agency regards invasive species as the number one threat to the Great Lakes. The exotic fish in the region are more problematic than pollution.

Asian Carp also exhibit a troubling behavior: they leap into boats, frightening and occasionally hurting boaters. Nobody wants a 100-pound fish coming at them unless it’s on the end of a fishing line!

In Florida, Grass Carp were released into lakes and ponds in 1972 as a biological control measure. The fish were introduced by state agencies in order to reduce the overgrowth of the exotic hydrilla, an aquarium plant, as well as other weeds. Only nonreproducing carp were used, the fish specially sterilized to be unable to breed.

Although these fish do help with undesirable aquatic vegetation because they have such healthy appetites, after the invasive plants are consumed the carp will eat all other available plant life. Once established in a lake or pond, Grass Carp are difficult to remove and they can live for 10 years or longer. During that time, they will consume large amounts of plant biomass. Also, a small percentage of the supposedly infertile Grass Carp have produced viable eggs.

The Florida Fish and Wildlife Conservation Commission encourages Florida anglers to fish for Asian Carp and help to reduce the populations around the state. Bait made from bread balls, dog food, corn, or biscuit mix (uncooked) appeal to these fish.

Federal and state wildlife authorities remind us to avoid stocking neighborhood lakes with Asian Carp or other exotic fish. Never dump the fish and plants from your aquarium or backyard pond into Florida waters. Remember, these activities are illegal and can result in fines and jail time. Not to mention the potential damage to our freshwater ecosystems and all the native wildlife dependent on them.

*John Fleshler, "Asian Carp raises concern on Great Lakes," South Florida Sun-Sentinel, December 11, 2009; Tom Henry, "Program aims to halt release of exotic fish," Toledo Blade, December 12, 2004; "Plant Management in Florida Waters," Center for Aquatic and Invasive Plants, www.ifas.ufl.edu

January 29, 2010: Green Anaconda captured in public park*

On January 13, a 12-foot long Green Anaconda was discovered in a park located in the Orlando area. The giant snake was captured by an Osceola County Sheriff’s mounted patrol unit training at East Lake Fish Camp. The sheriff’s deputies spotted the snake lying in a drain pipe. The reptile was slow and sluggish due to the cold weather, making it easier to trap. The huge reptile was transported to Reptile World Serpentarium in nearby St. Cloud.

People in the area had been reporting that the ducks and geese were disappearing, and park-goers suspected an alligator. Giant snakes on the loose are uncommon in central Florida, and Green Anacondas in the wild in our state are rare. In fact, there is only one other report on record of the capture of a feral Green Anaconda in Florida.

Feral giant snakes, notably pythons like the Burmese Python and the African Rock Python, have become a problem in Florida. Despite their rarity, Green Anacondas are also listed by the state as Reptiles of Concern, requiring permitting for ownership. Certainly, these huge snakes do not make good pets, and letting them loose in public parks is illegal. Dumping exotic animals of any species is a misdemeanor in Florida, one that can earn you a fine and a jail sentence.

*Jeannette Rivera-Lyles, "Anaconda captured at Osceola County fish camp," Orlando Sentinel, January 13, 2010

January 27, 2010: Florida fish death toll continues to mount*

Hundreds of thousands of Florida fish have died as a result of this month’s extended period of atypically cold weather. The bodies of fish, both fresh- and saltwater species, continue to float to the surface of our lakes and canals, bays and estuaries, even the open ocean.

Unlike the most recent record-setting chills in 1977 and 1989, January’s back-to-back cold fronts appear to have killed off some species thought to be cold-resistant. Fish tend to head for the warmer, deeper waters when cold weather settles in. The cold winds we experienced this year, however, pushed cold water into deep channels and canals. Thus, even some of the deep-water species were unable to survive.

Exotic species from South and Central America and Africa are the most vulnerable to cold temperatures. The Florida Fish and Wildlife Conservation Commission is reporting declines in the populations of Walking Cafish, Mayan Cichlids, and other tropical invaders. Environmentalists are pleased at the reduced threat to our native species from these non-natives, but wildlife officials see the cold-induced decline in numbers as temporary. Warm weather and the ongoing release of exotic fish into Florida waters will eventually lead to repopulation.

At this time, the total number of dead Florida fish, both exotic and native, is too large to estimate. An unestimable number of additional dead fish will float to the surface of our waters in the weeks to come, as weakened survivors succomb to infections. If you see a large quantity of dead fish, take note of the species and the average size. Then call in your findings to the Florida Fish Kill Hotline: 1-800-636-0511.

*Susan Cocking, "Thousands of dead fish fill Florida waters after cold snap," Boston Herald, January 20, 2010; Chris Morgan, "Cold inflicted major toll on Florida fish," Miami Herald, January 18, 2010

January 26, 2010: Dead iguanas floating in Florida waterways*

Reports are still coming in regarding the death toll for iguanas from this month’s unusually cold weather. Bloggers and chatroom visitors are discussing the many dead iguanas found floating in canals, lakes, and the Intracoastal waters of South Florida. Residents continue to clean up bodies from their sidewalks and driveways, yards and neighborhood parks, as the weakened reptiles gradually die off.

Although estimates for the total number of iguanas lost to January’s long chill are not yet available, Florida residents are aware that the burgeoning population of iguanas here has been dramatically reduced. This is a mixed blessing, as many homeowners have formed attachments to the friendly iguanas living in their neighborhoods. For wildlife officials, the sudden population reduction relieves the pressure to solve this particular non-native invasion issue.

However vast the death toll may turn out to be, it does not guarantee Florida’s iguana invasion is over.

Every year, an estimated one million iguanas are imported into the US by the pet trade. Most of these reptiles will die. Very few will survive in captivity for 10 years, which is half their natural life span. Very few will reach a healthy iguana’s natural size. Most will be kept in cages that are too small and which fail to provide adequate climbing area. Most will receive inadequate sunlight and improper nutrition.

And many will be released into the wild by owners who realize that owning an iguana requires more space, time and attention than they are able and willing to provide. Here in South Florida, where prolonged cold fronts only venture every few decades, the feral iguana population is sure to surge once more.

Iguanas do not do well in captivity. They also do not fare well in the wild when the temperature drops too low. It seems unfair for us to buy iguanas as pets, which encourages the importation of more and more of these vulnerable reptiles. It is also unfair for us to let them go when we realize how unsuitable they are to life in a cage.

*Jennifer Swofford, "Should I get an iguana? Or, the top 5 contributors to early iguana death," www.baskingspot.com

January 14, 2010: African Rock Pythons survive the freeze*

This week, licensed python hunters in the Everglades found five African Rock Pythons basking in the sun. Three of the huge snakes were captured, two escaped. One measured fourteen feet in length.

State wildlife officials believe this indicates a breeding population in the Everglades, rather than just a few abandoned pets. Biologists warn that the African Rock Python can mate with the Burmese Python, and there may be tens of thousands of the latter species on the loose in South Florida.

Crossbreeding creates a new environmental threat because the results are unknown. Since the African Rock Python tends to be nastier, more nervous and aggressive than the Burmese Python, herpetologists are not sure how a hybrid will behave in the wild. The hybrid snake may not be able to reproduce, but pythons can live 20 years or more. And they will need to consume a lot of our native wildlife, including birds, mammals and other reptiles. In its native Africa, the rock python eats animals as large as crocodiles.

The threat to humans from feral African Rock Pythons is of concern to state officials. Although there is only one documented report of the snake eating a human (a 10-year-old boy in South Africa), rock pythons do attack people. Even the juveniles are mean and feisty, and their bite is painful.

Unfortunately, two weeks of lower than average temperatures will not rid the state of dangerous exotic snakes. At this time, there does not appear to be a solution to our invasive reptile problem.

*Andy Reid, "Fears of 'super-snake' population in Everglades has python hunters on edge," South Florida Sun-Sentinel, January 13, 2010; "Scientists: African Rock and Burmese Pythons could mate in Florida Everglades," UPI, September 20, 2009; "Giant python swallows child in South Africa," Jet, December 16, 2002

January 11, 2010: Tropical animals suffer during cold snap*

For animals native to the tropics, a week of cold temperatures with nights dropping into the 30s can spell illness, immune system disorders, and death. Another reason why abandoning exotic pets in the wild in Florida is inhumane.

Reptile species native to tropical parts of the world have the most difficulty with cold waves because they are cold-blooded animals, unable to make their own body heat. Prolonged exposure to cold weather places metabolic demands on tropical reptiles that their bodies are unable to meet. This causes massive stress, physiological breakdown, and eventually death.

Iguanas around the state are frozen in place, clinging to trees and hiding in burrows in a state of suspended animation. The upcoming return to warmer weather will allow the ones who have survived the current record-breaking cold front to crawl back into the sun and attempt to recover. Some will sicken and die. State wildlife officials do not know what the overall effect will be on the iguana population in Florida, but the past week has definitely reduced their numbers.

The Florida Fish and Wildlife Conservation Commission (FWC) is urging licensed python hunters to take this opportunity to go look for the giant snakes in the designated hunting areas. Although these massive reptiles are able to maintain their body temperatures more efficiently than iguanas, pythons on the loose in Florida have been severely chilled. They are sure to seek sunny spots in which to bask, lying out in the open where hunters may be able to catch them.

Other non-native reptiles like Cuban Knight Anoles and Spectacled Caimans may have perished in significant numbers. Nature has taken its course, but the death toll for feral exotics in Florida is not natural. After all, pet-trading humans are responsible for removing these tropical animals from their natural habitats.

The tropical fish found in Florida’s waters will undoubtedly be reduced in numbers, too. Exposure to water temperatures of less than 52 degrees for days on end causes many non-native fish to sicken and die. Florida’s tropical fish farmers cover their ponds with plastic when the temperature drops, but last year and the year before saw massive die-offs when the thermostat dipped below freezing. This year’s extended cold front is expected to have dire consequences, both for the tropical fish farms and the many species of exotic fish loose in our waters.

Even our native animals are struggling with the unusually lengthy spate of cold weather. Hundreds of cold-stunned sea turtles have been rescued by wildlife experts, and manatees are hovering in the 92 degree water found in discharge canals at the state’s power plants. FWC has received reports of cold-related fish kills, with losses of warm-water species like snook.

Fortunately, more typical Florida weather is returning to the state this week. Florida’s wild animals, native and not, will have a chance to warm up.

Patrik Jonsson, "Snow in Florida: Big chill culling unwanted iguanas and pythons," Christian Science Monitor, January 9, 2010; Emily Nipps, "A cold week for Florida critters, too," St. Petersburg Times, January 9, 2010; "FWC reminds hunters: cold weather means pythons are sunning," www.myfwc.com, January 8, 2010; "Cold temperatures impact Florida fish and wildlife," www.myfwc.com/NEWSROOM, January 7, 2010; Catherine E. Shoichet, "Cold lethal for tropical fish stocks," St. Petersburg Times, March 7, 2008

January 7, 2010: Frozen iguanas may die in large numbers*

Like tourists from warmer climes, the exotic iguanas on the loose in Florida do not do well in cold weather. The three species of iguana running free around the state--Green Iguana, Mexican Spinytail Iguana, and Black Spinytail Iguana--have been relocated here by the pet trade and are native to South and Central America. They have not evolved here so have difficulty weathering Florida’s occasionally chilly winter temperatures.

Iguanas are cold-blooded reptiles. A short period of frigid weather will slow down an iguana’s metabolism, allowing the animal to immobilize in an energy-saving state of suspended animation. Iguanas will hide in burrows in the ground or up among the tree branches to avoid predators while semi-frozen. Some will fall out of trees when they are no longer able to cling to trunks and branches. Dropping iguanas may not be dead, just stunned. A good tumble can awaken some iguanas from their frozen stupor, and they will scurry away.

Once the sun comes out, iguanas are able to warm up, their metabolic rate and other functions gradually returning to normal. However, prolonged exposure in an extended period of cold weather, with night after night of temperatures dipping into the 30s and low 40s, can prove fatal for iguanas. For example, with the ongoing cold front that has been hovering over South Florida, state wildlife biologists are predicting that many feral iguanas will die. The larger, older iguanas might be able to suffer through, as they have already been able to survive past winters of unseasonable weather (iguanas can live 20 years). But the smaller, more vulnerable juveniles and less hearty iguanas will not be able to withstand the prolonged cold.

Some homeowners are taking advantage of the iguanas’ helpless state to trap and remove them from their yards. Others are trying to save the poor creatures, covering unmoving reptiles with blankets and hoping they make it through the night.

Local weather forecasters are calling for another frigid dip over the weekend, extending the cold stretch into the longest in a decade. The vultures are circling, watching and waiting to see what happens to the South Florida exotic iguana population.

*Thalia Hayden, "Iguanas are freezing," WPTV.com, January 6, 2009; Linda Trischitta, "Extended cold front could kill invasive iguanas," South Florida Sun-Sentinel, January 4, 2009

January 1, 2010: Hand in your nasty reptile and avoid the fine*

A few weeks ago, the Florida Fish and Wildlife Conservation Commission (FWC) announced an executive order that will allow unpermitted and unwanted reptiles of concern (ROC) to be turned over to authorized permit holders. The potentially dangerous pets will be accepted by amnesty program members with “no questions asked,” enabling owners to avoid the legal penalties for failure to permit Nile Monitor lizards, Green Anacondas, Burmese Pythons, African Rock Pythons, Reticulated Pythons, and Scrub (Amethystine) Pythons.

The ROC amnesty program has been specially designed so that it will be easy both to hand in an unwanted animal and to accept one from those who no longer wish to care for it. All licensed reptile handlers will be able to accept donated reptiles of concern under the new program. Anyone who holds a license for ownership of reptiles of concern will be eligible for the operation of a ROC amnesty facility once the executive order is issued sometime this year.

Since the state has begun to increase the regulation of invasive reptiles, the potential for mass dumping of illegal snakes and lizards has become an issue. Breeders and dealers, as well as reptile enthusiasts, may be tempted to avoid permit fees and penalties by releasing their animals in the wild. The ROC amnesty program should help to prevent the safety and environmental disasters that would emerge if more giant lizards and snakes were to be abandoned in parks and neighborhoods around the state. It is already impossible for us to eradicate all the exotic animals on the loose in Florida. The FWC is hoping that, with some leniency, at least a measure of control will be feasible.

*Tim Breault, "FWC orders amnesty program for reptiles of concern," www.myfwc.com News Release, December 10, 2009

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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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