STANDARDS

NGSS: Core Idea: LS3.B

CCSS: Reading Informational Text: 9

TEKS: 6.12F, 7.10A, 8.11C, B.11D

Croc Invasion

Nile crocodiles have been spotted in Florida—far from their native home

September 19, 2016

By Adam Hadhazy

ESSENTIAL QUESTION: How might a species of crocodile invading Florida cause problems for people and the wildlife there?

More than 100 million tourists flock to Florida every year. But in recent years the state has had some unwelcome visitors as well—dangerous Nile crocodiles, normally found in Africa. Three of the animals have been found since 2009. But only now have scientists confirmed that the reptiles were indeed Nile crocs.

Nile crocodiles are larger and more aggressive than Florida’s native crocodiles and alligators. The crocs are just one of many invasive species in the U.S. (see America’s Least Wanted). These plants and animals have been introduced to areas where they don’t normally live. If they can thrive in their new homes, they can become serious threats to local ecosystems.

More than 100 million tourists flock to Florida every year. But lately the state has also had some unwelcome visitors. Dangerous Nile crocodiles normally live in eastern Africa. But three have turned up in Florida since 2009. Scientists have now confirmed that they’re Nile crocs.

Florida has its own alligators and crocodiles. But Nile crocodiles are larger and more aggressive. The crocs are one of many invasive species in the U.S. (see America’s Least Wanted). These plants and animals have turned up in places where they don’t normally live. Some of them do well in their new homes. If that happens, they can cause serious problems for local plants and animals.

Invasive Species

Watch a video describing the harmful effects of invasive species on the environment.

ANIMAL I.D.

Between 2009 and 2014, three young crocs with unusual coloration were captured in Florida. “We suspected they weren’t native,” says Kenneth Krysko, who studies reptiles at the Florida Museum of Natural History, “so we tested their DNA.” Scientists can use this molecule, which carries an organism’s hereditary information, to identify a species. The genetic tests have revealed that the animals were, in fact, Nile crocodiles.

Florida’s Fish and Wildlife Conservation Commission traced the animals to a private residence. Its owner, who had plans to open an attraction called Predator World, had improperly caged the crocs, and some of them escaped.

Three unusual crocs were captured in Florida between 2009 and 2014. The young animals had a different color pattern from that of local crocs. Kenneth Krysko studies reptiles at the Florida Museum of Natural History. “We suspected they weren’t native,” he says, “so we tested their DNA.” This molecule carries an organism’s hereditary information. Scientists can use it to identify a species. The DNA tests revealed that the animals were Nile crocodiles.

Florida’s Fish and Wildlife Conservation Commission traced the animals to a private home. Its owner had plans to open an attraction called Predator World. But the crocs weren’t caged properly. Some of them escaped.

A BIG PROBLEM

In Africa, Nile crocs have a wide range—the geographical area where a species lives. They could probably survive anywhere in Florida. The three captured ones spent years on the loose before being spotted. And since no one is actively searching for Nile crocs in the state, Krysko says others could be running wild there.

The discovery of Nile crocodiles in Florida has brought more attention to the broader issue of invasive species. “I think this will open people’s eyes to the problem,” says Krysko.

In Africa, Nile crocs have a wide range—the area where a species lives. They could probably survive anywhere in Florida. The three captured ones were loose for years before being spotted. And no one is searching for Nile crocs in the state. So Krysko says others could be running wild there.

The discovery of Nile crocs in Florida brings attention to the bigger issue of invasive species. “I think this will open people’s eyes to the problem,” says Krysko.

AMERICA'S LEAST WANTED

Thousands of invasive species currently live in the U.S. Here are a few of the worst offenders.

HUGO WILLCOX/FOTO NATURA/MINDEN PICTURES

NUTRIA

These buck-toothed rodents were imported from South America in the 1940s so they could be hunted for their fur. But the population has since multiplied out of control. Nutria eat the plants in swamps. That leaves native animals, like muskrats, without a home or food. To fight back, officials trap the animals—and even try to get people to eat them!

NUTRIA

M. SPENCER GREEN/AP PHOTO

ASIAN CARP

Asian carp were introduced to the U.S. in the 1970s to eat algae in fish farms in the South. But in the 1990s, the fish escaped during floods. They moved up the Mississippi, Illinois, and Ohio rivers. There, they consume food native fish need to survive. Officials are now using electric fences and other tactics to try to keep the carp out of the Great Lakes.

ASIAN CARP

AGE FOTOSTOCK/ALAMY STOCK PHOTO

MONGOOSE

Mongooses were brought to Hawaii in the 1880s to eat another invasive species: rats. But the weasel-like critters started eating native species instead. They almost drove Hawaii’s state bird, the nene, to extinction. Traps and poison have failed to control them so far.

MONGOOSE

CHRIS NEWBERT/MINDEN PICTURES

LIONFISH

These frilly fish are from the south Pacific Ocean. They invaded the Atlantic coast in the 1990s when aquarium owners dumped them in the ocean. Since then, the invaders have gobbled up millions of native fish and other ocean species. New programs encourage people to catch and eat the pesky fish.

LIONFISH

ALAMY STOCK PHOTO

BURMESE PYTHON

These snakes from Asia were brought to the U.S. as pets. But many escaped or were released into the wild by irresponsible owners. Upwards of 10,000 of the pythons now live in southern Florida. The predators, which can grow to more than 4.6 meters (15 feet) long, eat many species, like deer, rabbits, and even bobcats. Scientists are tracking the giant snakes to find new ways to control them.