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Invasive Herpetofauna of the Everglades and South Florida
Aliens have arrived. They have been here for decades. They are living among us. They are slowly taking over rivers, forests, wetlands, and even the suburbs. No, the aliens I speak of are not from a distant galaxy, or even a nearby planet. These aliens, also known as exotic or invasive species, are from nearby islands and different continents. Many species are included in the list of invasives from many different taxa. Among these taxa there are many species of reptiles and amphibians that have become established in South Florida and the Everglades with various impacts to local ecosystems.
Invasive Species Examples
The invasive species of South Florida and the Everglades include several frog specis such as Cuban Treefrogs (Osteopilus septentrionalis) and Greenhouse Frogs (Eleutherodactylus planirostris) natives of Cuba. Cane toads (Bufo marinus), also known as Marine toads and Giant toads, are prevalent in many parts of Florida, and natives of Central America. Coqui frogs (Eleutherodactylus coqui) are native to Puerto Rico and was introduced to Miami Florida, New Orleans, and the Virgin Islands (Conant and Collins, 1998).
Examples of invasive snakes in South Florida and the Everglades are Burmese Pythons (Python molurus bivittatus) are from Southeast Asia and a major part of the pet trade. Brahminy blind snakes (Ramphotyphlops braminus) are also from Southeast Asia and have become prevalent in Florida, and even recorded in Ohio. Javan filesnakes (Acrochordus javanicus) have been reported for decades in Florida and are originally from India and parts of Southern Asia (Conant and Collins, 1998).
There are also many species of lizards that are alien to Florida including Northern Curly Tailed Lizards (Leiocephalus carinatus), which are native to the Bahamas; Green Iguanas (Iguana iguana), native to Central America; Monitor Lizards (Varanus nilotictus) native to Africa; many species of anoles (Anolis spp.) native to the Caribbean; and Brown Basilisks (Basiliscus vittatus), native to Central America. There are also 14 species of gecko found in Florida, of these only one is native, the Florida Reef Gecko. The others live primarily in small ranges, primarily around Miami and Tampa, and have come from many countries and continents. There is one species of crocodilian that is invasive to parts of Florida, the Spectacled Caiman (Caiman crocodiles), from South America. (Conant and Collins, 1998).
Problems with Invasives
Cuban Tree Frogs
To fully understand the problems associated with these invasive species more information of their life history is necessary. The Cuban Tree frog for example was likely a stow away in shipments of plants or produce from Cuba. This species have very destructive habits as they eat native frogs and the prey items of native species, out competing them for food. It has also been noted that in areas where Cuban Tree Frogs become dominant there are few native frog species that survive in the area as they are eaten or out competed for resources. (FFWCC, 2004)
Additionally, Cuban tree frogs have been known to cause power outages and water problems as they often hide in water softeners and can short them out. This species has toxic skin secretions, so predators of native frogs and toads are unable to eat them. This is a problem because it shows the natural system of population checks and balances to maintain healthy populations of species within an ecosystem is not functioning correctly. If a way of controlling the population of Cuban tree frogs is not found, many amphibian species in South Florida and the Everglades may suffer large population losses. (FFWCC, 2004)
A second, more detailed example of invasive species taking over in South Florida and the Everglades is the Burmese Python. This is a species that was introduced to the area when people released their pet pythons once they grew too large. Miami Florida is one of the largest importing cities in the country of exotic snakes. Many people buy Burmese Pythons when they are young and small, without considering what they will do with them once they grow full size at 20 feet and 200 pounds! For many people they are unable to care for the snakes once they grow large, and there are no zoos looking for these large snakes and no other places to sell them, so they release them into the Everglades. (FFWCC, 2004; Pough, 2003; Lovgren, 2004)
For the past 20 years Burmese Pythons have been recorded in the Everglades (National Geographic). In the past decade there has been confirmation by the National Park Service that the snakes are breeding in the park. These snakes have become a problem because they are now apex predators in the ecosystem. They prey upon animals ranging from frogs, to rabbits, to raccoons, and even to alligators. Because they are a sit and wait predator they could also attack humans given the opportunity. (FFWCC, 2004; Pough, 2003; Lovgren, 2004)
There has been increased pressed coverage of these snakes in the Everglades recently as they have been photographed fighting and eating alligators. The most notable picture recently was the photo of a 12 foot long python that had bust its gut from the 6 foot alligator that it had swallowed. This event, along with tourist sightings of several alligator versus python fights, has drawn a great deal of media and public attention to the problem of this invasive species in recent years. With more public awareness there may, hopefully, be more efforts put into finding a control for these huge snakes and prevent them from continuing their population growth. (FFWCC, 2004; Pough, 2003; Lovgren, 2004)
The Nile Monitor Lizard
Nile monitor lizards are native to Africa, and much like the Burmese python, they have been introduced in South Florida as a by-product of the pet trade. They were probably introduced to South Florida either by pet owners getting rid of a pet that has gotten too large to handle, a pet trader establishing a local population to draw from for selling, or a combination of the two. (FFWCC, 2004; Pough, 2003)
This large carnivorous species, which grows up to 7.5 feet, can dig up reptile eggs (including those of crocodilians and sea turtles) and prey upon birds, mammals, frogs, lizards, snakes, fish, and crabs. Cape Coral has the largest Florida population of burrowing owls (>1,000 pairs), which might be impacted by monitors usurping their burrows and preying upon adults, nestlings, and eggs. (FFWCC, 2004; Pough, 2003)
The species is thought to be capable of living in any vicinity of water, leaving all riparian areas, agricultural areas, wetlands, and coastal areas as possible areas for the species to live. In the past ten years it has only been known to exist as a breeding population in one county, although it has been recorded in six others. (FFWCC, 2004; Pough, 2003)
This is a species that could be a danger to humans as they grow large enough to attack a human and would be very willing if hungry enough or cornered. There have been attempts to control this population via trapping to euthanise and to cycle into the pet trade; however, because the population is breeding and seems to be adapting very well to the environment in South Florida the attempts do not seem to be very successful. (FFWCC, 2004; Pough, 2003)
Are all invasive species bad?
Lake Erie Water Snakes and the Gobi
While the negative aspects of invasive species have been highlighted here, there is also a need to consider whether all invasive species have negative impacts on ecosystems. The Lake Erie water snake (LEWS) (Nerodia sipedon insularium) was on the brink of extinction, but recent research suggests their come back is based largely on their diet of invasive round gobi fish that have become abundant in Lake Erie. At the same time these fish have been implicated as possible causes of declines in other species.
So are invasive species a threat to local ecosystems, or can they serve as positive influences in those systems? The first instinct of most scientists is to say they are threatening to ecosystems. Time may tell a different story. As globalization continues species are not confined by oceans, rivers, or mountains as they once were. With time, we may come to understand how the aliens will impact the global ecosystem, and with that we may understand how the growth of society will impact our Earth as well.
1. Conant, Roger; Collins, Joseph T. 1998. Peterson Field Guides: Reptiles and
Amphibians of Eastern/Central North America 3rd Ed. Houghton Mifflin Co. New York, New York.
2. Pough, H.F.; Robin M. Andrews; John E. Cadle; Martha L. Crump; Alan H. Savitsky;
Kentwood D. Wells. 2003. Herpetology, 3rd Ed. Prentice Hall. New York, New York.
3. Lovgren, Stefan. Huge Freed Pet Pythons Invade the Everglades. National Geographic
Magazine. Online. Published June 2004. Accessed on 6 June 2006. http://news.nationalgeographic.com/news/2004/06/0603_040603_invasivespecies.html
4. Florida Fish and Wildlife Conservation Commission (FFWCC). 2004, June 4. Florida's
Exotic Wildlife. http://myfwc.com/critters/exotics/exotics.asp (Date accessed 6/6/2006).
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