Florida's invasive amphibian and reptile problem leads world

November 2nd, 2011

By Danielle Torrent

Burmese Python

The Burmese python is Florida’s largest invasive species documented in a recent study led by Florida Museum researcher Kenneth Krysko. © Photo by Eric Zamora

 

During the 1800s, the world was going through transformations steered by war, invention, scientific innovation and the discovery of new land. The time period saw the collapse of some empires and the rise of others, from the British and Japanese to the booming United States of America. The Industrial Revolution brought about the invention of railroads, and cargo ships made an unprecedented number of journeys to the New World. But unbeknownst to conquerors, amphibians and reptiles were along for the ride, and their presence is having a seemingly irreversible impact today.

In Florida, it started with the first documented introduction of the Greenhouse Frog in 1863, a native of the West Indies. This species has become widespread and occurs in areas where many native frogs are now seldom seen. Circa 1887, cargo ships brought the brown anole from Cuba to the state, and the small, brown lizard is now one of Florida’s most easily recognized wildlife species. The state’s largest established invader, the Burmese Python, made its way from the rainforests of Southeast Asia to become household pets for Floridians, and recent studies show the devastating effects these up to 20-foot-long creatures have on native wildlife in the Everglades. In total, Florida has seen at least 137 introductions of non-native amphibians and reptiles, more than anywhere else in the world.

“Most people in Florida don’t realize when they see an animal if it’s native or non-native and unfortunately, quite a few of them don’t belong here and can cause harm,” said Kenneth Krysko, Florida Museum of Natural History herpetology collection manager and lead author of a 20-year study published in Zootaxa Sept. 15, 2011, documenting all known introductions to the state from 1863 to 2010. “No other area in the world has a problem like we do, and today’s laws simply cannot be enforced to stop current trends.”

Until about 1940, the introductions were incidental, primarily resulting from the cargo trade. But in the 1970s and ’80s, pet dealers began importing more species to meet the boom in popularity of exotic terrarium animals. The study attributes 84 percent of the introductions to the pet trade, with 25 percent traced to one animal importer.

“If the trends continue, it’s likely we will have more non-native species in Florida than native species,” Krysko said. “It’s really difficult to comprehend, but I believe it can happen.”

Florida law prohibits the release of non-native species without a state permit, but offenders cannot be prosecuted unless they are caught in the act. To date, no one in Florida has been prosecuted for the establishment of a non-indigenous animal. Researchers urge lawmakers to create enforceable policies before more species reproduce and become established. The study names 56 established species: 43 lizards, five snakes, four turtles, three frogs and a caiman, a close relative of the American alligator.

“The invasion of lizards is pretty drastic considering we only have 16 native species,” Krysko said. “Lizards can cause just as much damage as a python. They are quicker than snakes, can travel far, and are always moving around looking for the next meal.”

Defined by the U.S. Department of Agriculture as organisms “whose introduction causes or is likely to cause economic or environmental harm or harm to human health,” invasive species are a growing concern for residents and policymakers. Only three species were intercepted before reaching the wild and the study also shows no established, non-native amphibian or reptile species has been eradicated.

Other pathways include biological control, in which an animal is intentionally released to control a pest species, and accidental introduction through the zoo or plant trade. The study will serve as a baseline for establishing effective policies for control or eradication, said Fred Kraus, a vertebrate biologist at the Bishop Museum in Honolulu who helped establish policies for invasive amphibians and reptiles in Hawaii.

“This paper by Kenney and company I think is a good example of the approach that needs to be taken, providing the detail and being rather cautious in making immediate claims that things are established until there is evidence for it,” Kraus said. “There is a lot more work going on now, but for years it was just ignored. For years, climate change was ignored, too. You know, humans just tend to ignore bad news until you can’t ignore it anymore.”

Ecological impacts

Kenny Kryston holds chameleons

Krysko displays non-native Jackson’s chameleons, a species whose population numbers continue to increase in Florida. © Photo by Anthony T. Reppas

Floridians have experienced some of the damage these animals can cause, from iguanas that destroy cement foundations to Burmese pythons released in the Everglades that eat protected species. While the impact of many of the introduced species has not been determined, the study provides new information about how, why and when they entered the state.

“It’s like some mad scientist has thrown these species together from all around the world and said, ‘hey let’s put them all together and see what happens,’ ” Krysko said. “It could take decades before we actually know the long-term effects these species will have.”

Krysko’s study is the first comprehensive documentation of all of Florida’s amphibian and reptile introductions, and ecological impacts will need to be compared to this research in the future. A similar area for comparison to Florida is sub-tropical Guam, where a 40-year observation shows the invasion of the brown treesnake has caused human health risks, negative impact on the economy and the loss of 11 of Guam’s 13 native land birds.

“Ecologically, native species have more of a right to be here than even humans do,” Krysko said. “They evolved here in this area much earlier and really, we should be recognizing the native organisms as being more important than anything else.”

How to help

Iguana

Non-native iguanas dig burrows that damage cement foundations and sea walls. Some green iguanas, such as this one photographed at a front door in Lake Worth, Fla., have lost their fear of humans and are often drawn to houses where pet food is left outside. © Photo by Carl May

One of the greatest obstacles pet owners face is how to feed and house an exotic animal that has become too large or difficult to handle, Krysko said. Adoption of a pet that triples in size upon adulthood should only be carried out after careful research to learn how large an animal will grow, its potential life span, and the amount of care it requires, according to the Florida Fish and Wildlife Conservation Commission. The agency’s website offers different options for exotic pet owners that can no longer care for their animals, including information about pet amnesty days, in which exotic pets may be turned in to the FWC.

Citizens may also help Florida’s invasive species problem by reporting sightings and introductions of exotic animals. With an accurate baseline of what exists, researcher will be able to more effectively document the effects non-native animals have on wildlife and the economy.

“I’m hoping this paper will sort of help nudge the field forward and get people to recognize that greater compilations like this have a use,” Kraus said. “It’s not just a matter of enforcement; you need better prevention, rapid response and better detection, and better long-term control of the widespread things.”

The study uses fieldwork data from 12 co-authors throughout the state and research primarily using collection specimens from the Florida Museum of Natural History, located on the University of Florida campus in Gainesville. Study co-authors include Joseph Burgess of the Florida Department of Environmental Protection; Michael Rochford and Guy Kieckhefer, III of UF’s Fort Lauderdale Research and Education Center; Christopher Gillette and Daniel Cueva of Florida International University; Kevin Enge of the Florida Fish and Wildlife Conservation Commission; Louis Somma, a Florida Museum herpetology volunteer; Jennifer Stabile of the Central Florida Zoological Park; Dustin Smith of Zoo Miami; Joseph Wasilewski of Natural Selections; Michael Granatosky of the Florida Museum and Duke University; and Stuart Nielsen of the University of Mississippi.

“This is a global problem and to think Florida is an exception to the rule is silly,” Krysko said. “The Fish and Wildlife Commission can’t do it alone – they need help and we have to have partners in this with every agency and the general public. Everyone has to be on board; it’s a very serious issue.”

 


Published on Science Stories: November 2011.