Why Have So Many Animals Invaded Florida?

In Florida, if you want to see a furry vervet monkey or a massive Burmese python up close, you don’t need to visit a zoo: Just take a walk! You might spy a monkey hanging from a tree or a snake as long as a minivan slithering through the grass. Even though these animals are not from this state, they’ve made it their home. And they have plenty of company. There are nearly 600 nonnative species in Florida—more than any other state in the U.S. 

Many of these creatures are invasive, meaning they cause harm to the local environment, economy, or people. Some invasive species, like green iguanas, seem to be little more than a nuisance. Iguanas mostly dig holes in gardens and nibble on plants. But other species are causing serious problems for local wildlife. The tegu lizard, for example, eats the eggs of American crocodiles and other native species—some of which are endangered, or at risk of going extinct.

To deal with Florida’s growing problem, some scientists are trying to catch and remove certain nonnative species as fast as they can. But others think it’s too late to reverse the flood of invaders. If so, what does that mean for Florida’s residents and native wildlife?

You usually have to visit a zoo to see a furry vervet monkey or a massive Burmese python up close. But in Florida, you can just take a walk! You might spy a monkey hanging from a tree. Or a snake as long as a minivan might slither through the grass. These animals are not from this state, but they’ve made it their home. And they have plenty of company. Nearly 600 nonnative species live in Florida. That’s more than any other U.S. state. 

Many of these creatures are invasive. They cause harm to the local environment, economy, or people. Some invasive species cause small but annoying problems. Green iguanas are one example. They mostly dig holes in gardens and nibble on plants. But other species cause serious problems for local wildlife. For example, the tegu lizard eats the eggs of American crocodiles and other native species. Some of these species are endangered, or at risk of going extinct.

The problem in Florida is growing. So some scientists are trying to catch and remove certain nonnative species as fast as possible. But others think it’s too late to reverse the flood of invaders. If so, what does that mean for Florida’s residents and native wildlife?

Burmese pythons come from Asia. Green iguanas hail from South and Central America. They didn’t end up in Florida by choice—people brought them to the state as part of the exotic pet trade. Compared with other states, Florida has less strict laws about which exotic animals can be kept as pets. But captive creatures don’t always remain captive. A hurricane might knock down a roadside reptile attraction, allowing the animals to escape. A snake owner might decide they no longer want to care for a creature that’s grown longer than their living room, so they release it into a nearby swamp. “Florida is hot and wet: ideal conditions for many animals,” says biologist Adam Rosenblatt from the University of North Florida (see Unwanted Neighbors). Once out in the wild, these animals can thrive, eating everything from garden plants to native creatures.

Experts rank Burmese pythons as one of Florida’s least-wanted invasive species. That’s because “they’re eating machines,” says Ian Easterling, a biologist at the Conservancy of Southwest Florida. The pythons are especially abundant in and around Florida’s Everglades National Park, where they prey mainly on medium-size mammals. Because of the snakes’ huge appetite and vast numbers, says Easterling, “you’d be hard-pressed to find a single raccoon in all of the park.” When invasive predators wipe out native animals, that affects the entire ecosystem—the community of organisms interacting with their nonliving environment.

Burmese pythons come from Asia. Green iguanas are from South and Central America. They didn’t choose to come to Florida. People brought them to the state as part of the exotic pet trade. States have laws about which exotic animals can be kept as pets. But Florida’s laws are less strict than others. And captive creatures don’t always remain captive. A hurricane might knock down a roadside reptile attraction. Then the animals can escape. A pet snake might grow longer than the living room, and its owners no longer want to care for it. So they release it into a nearby swamp. “Florida is hot and wet: ideal conditions for many animals,” says biologist Adam Rosenblatt from the University of North Florida (see Unwanted Neighbors). Out in the wild, these animals can thrive. They eat everything from garden plants to native creatures.

Burmese pythons are one of Florida’s least-wanted invasive species, experts say. That’s because “they’re eating machines,” says Ian Easterling. He’s a biologist at the Conservancy of Southwest Florida. Many Burmese pythons live in and around Florida’s Everglades National Park. There, they prey mainly on medium-size mammals. The snakes have huge appetites and vast numbers. Because of that, “you’d be hard-pressed to find a single raccoon in all of the park,” says Easterling. When invasive predators wipe out native animals, this affects the entire ecosystem. That’s the community of organisms along with their nonliving environment.

One solution is to try to remove as many individuals of an invasive species as possible. Easterling is part of a team that aims to reduce the numbers of Burmese pythons—but it’s no easy job. Easterling and his colleagues slash through dense forest with machetes and wade through murky swamps. They look for female snakes to capture and remove from the wild. This prevents the pythons from laying dozens of eggs that would hatch into even more snakes. “The biggest one we’ve caught was 5.4 meters [18 feet] long and weighed 98.5 kilograms [215 pounds]—more than me!” says Easterling.

Over the past 10 years, the team has captured more than 1,000 snakes. But scientists say there could be as many as 100,000 Burmese pythons on the loose in South Florida, and their range is expanding (see Pythons on the Move). Experts agree that catching all of the snakes is probably impossible. And some think it’s not worth the time, money, and effort to even try. “Eliminating an invasive animal has rarely worked, unless it’s on an island,” says Sean Doody, a conservation biologist at the University of South Florida. That’s partly because on an island, animals are confined by its natural borders.

Doody argues that in Florida, scientists should first figure out the impacts of different nonnative species on their environments in the state and then decide whether it’s worth trying to remove them. “We’ve got some that aren’t doing any harm, some that are, and a whole lot we have no idea about,” says Doody. Other experts say that by the time such studies are finished, invasive populations will already have grown out of control.

One solution is to remove as many individuals of an invasive species as possible. Easterling is on a team that aims to reduce the numbers of Burmese pythons. But it’s no easy job. Easterling and his team slash through dense forest with machetes. They wade through muddy swamps. When they find female snakes, they capture and remove them from the wild. This prevents the pythons from laying dozens of eggs. Those eggs would hatch into even more snakes. “The biggest one we’ve caught was 5.4 meters [18 feet] long and weighed 98.5 kilograms [215 pounds]—more than me!” says Easterling.

The team has captured more than 1,000 snakes in the past 10 years. But scientists say that up to 100,000 Burmese pythons could be loose in South Florida. And their range is growing (see Pythons on the Move). Experts agree that they probably can’t catch all of the snakes. And some think it’s not worth the time, money, and effort to even try. Sean Doody is a conservation biologist at the University of South Florida. “Eliminating an invasive animal has rarely worked, unless it’s on an island,” he says. That’s partly because animals can’t leave an island.

Doody argues that scientists should learn the effects of different nonnative species on their environments in Florida. Then decide whether to try to remove them. “We’ve got some that aren’t doing any harm, some that are, and a whole lot we have no idea about,” says Doody. Other experts say that such studies will take too much time. By then, invasive populations will already be of control.

No one thinks it’s a good idea to just let Florida’s nonnative animals run wild like a science experiment gone wrong. Experts agree that fighting back against the most harmful species in targeted areas is a good idea. For example, the program Easterling works with focuses on a relatively small 390 square kilometer (150 square mile) area of southwest Florida. Many people live there, and pythons have been known to terrify residents, threaten people’s pets, and even eat small livestock.

No one wants to let Florida’s nonnative animals run wild like a science experiment gone wrong. Experts agree on one idea. They should fight back against the most harmful species in targeted areas. The program Easterling works with is an example. It focuses on a relatively small part of southwest Florida. Many people live in this 390 square kilometer (150 square mile) area. Pythons have terrified the residents, threatened people’s pets, and even eaten small livestock.