A red-eared slider turtle at the Cincinnati Zoo. Greg Hume/Wikimedia Commons
We hear a lot about invasive species in the United States, but we also do our fair share of exporting species that damage ecosystems around the world.
Many of these made-in-the-U.S.A. animals start as seemingly innocuous pets. Others escape from farms. All of them out-compete native species and prosper in the lands they invade.
Red-eared sliders rose from humble beginnings on the muddy banks of the Mississippi River and surrounding waterways. The turtles achieved international fame as the most popular pet turtles worldwide. The United States exported fifty-two million turtles between 1989 and 1997 during the peak of the Teenage Mutant Ninja Turtles craze, according to the European Network on Invasive Alien Species (NOBANIS).
Now, red-eared sliders live on every continent except Antarctica. Sliders can grow to approximately 30 centimeters (1 foot) and live for four decades. Their large size and longevity wears out their welcome as pets, so they're often released. In the wild, the liberated sliders dominate many native turtles, including the endangered Spanish terrapin (Mauremys leprosa) and European pond turtle (Emys orbicularis).
An American Lobster, Homarus americanis, on the Atlantic coast of North America.David Wrobel/Corbis
New England's iconic American lobster (Homarus americanus) seems to be a conquering crustacean. American lobsters first appeared in Europe in 1999 and have spread since then. Thriving American lobsters in European waters means bad news for the native lobsters (Homarus gammarus) and fishermen. American lobsters harbor diseases than can kill the native crustaceans or cause deformations to their shells, which reduces their market value.
A study published in BioInvasion Records documented 26 American lobsters positively identified in the coastal waters of Great Britain as of 2011. The Yankee lobsters spread north as well. In 2010, the animals were captured in Norwegian waters. These invaders not only carried the shell disease, but also seemed to be interbreeding with the local lobsters, according to Invasive Species Compendium of CAB International, an EU inter-governmental organization.
An American Bullfrog is seen in a mating pond at the Jurong Frog Farm in Singapore December 11, 2008. The only frog breeder in the city-state breeds bullfrogs primarily for human consumption.Corbis
Like red-eared sliders, the bullfrog of the eastern and southern U.S. rose from the muck of the Mississippi to take over the world. France, Brazil, the western United States, China, Japan, Cuba and many other nations' waterways fell to the invading frog. Suitable habitat for bullfrogs stretches over an even wider area of the planet, according to research in Diversity and Distributions.
Invading bullfrogs bring a reliable food source along with them...their own children. Bullfrogs eat anything that fits in their mouths, including their own tadpoles and small bullfrogs. The young eat algae and insects, then the adults eat them. Those that survive to adulthood breed prolifically and start the process over.
Perhaps humans can turn the tables on the frogs. Fried or roasted bullfrog legs taste like chicken's white meat in the form of a tiny drumstick. The study in Diversity and Distributions noted that bullfrog invasions were less successful in areas where humans heavily hunted the hopping habitat homewreckers.
Gray squirrel leaping with a nut in its mouth in Derbyshire, England.Andrew Parkinson/Corbis
Winston Churchill might have said that the British will never, never give up in their fight against American gray squirrels. They shall fight in the fields and in the streets and in the treetops.
The British revile the rodent interloper because it threatens the native red squirrel. Prince Charles himself has joined the crusade, calling the red squirrel, "the most iconic of species," reported the Telegraph. Gray (or should it be grey) squirrels have largely displaced the reds. An estimated 140,000 red squirrels survive on the sceptered isle, according to the Forestry Commission. However, more than 2.5 million grays scurry through British trees. Despite the fall of Britain to the grays, red squirrels remain common in mainland Europe and Asia.
Raccoon licking its mouth after raiding a trash can in a public park.R. Al Simpson/Corbis
The trashcans of Europe and East Asia face a grave threat. Raccoons now prowl Germany, Japan, France and many central and eastern European nations. Beyond raiding the garbage, raccoons threaten human health. Raccoons in Germany tested positive for rabies and roundworm parasites, according to the European Network on Invasive Alien Species (NOBANIS).
Raccoons had accomplices in their invasion of Europe. A German man intentionally released raccoons into his homeland's forests in 1927. Even more raccoons escaped during World War II from fur farms near Berlin. In Russia, the animals were intentionally released with the goal of establishing populations for fur trapping and hunting. The 'coons found the north coast of the Black Sea particularly inviting and now thrive there and in the Caucasus region.
An American mink on beach shore. Needsmoreritalin, Wikimedia Commons
Like the raccoon, the American mink also got its chance at world domination after escaping or being released from fur farms. The American mink now hunts the native animals of Russia, Italy, Ireland, Scotland, Britain, Iceland, Chile, and Argentina.
In Europe, the American mink (Neovison vison) poses a serious challenge to the European mink (Mustela lutreola), critically endangered species on the International Union for the Conservation of Nature Red List. American minks grow larger and don't depend on wetland habitat as much as European minks, which gives the invaders an advantage.
A crayfish platter served at a restaurant. Olaf, Wikimedia Commons
Whether you call them crayfish or crawdads, people in East Africa call them trouble. People intentionally released the Louisiana crayfish (Procambarus clarkii) into man-made wetlands. The mini-lobsters were intended to control snails harboring the parasite that causes schistosomiasis. However, the plan went awry after the crustaceans escaped and spread to natural wetlands.
In one African lake, another invasive species stepped up to knock out the crayfish. In Lake Naivasha, Kenya, common carp from Asia took over the ecosystem. Besides dominating the native fish, a study in PLOS ONE found that the carp also wiped out the crayfish from the lake.
If the carp aren't sufficient to knock out the crayfish, perhaps a few Cajun chefs could do the trick.
A largemouth bass gets hooked on a line.F Eugene Hester, U.S. Fish and Wildlife Service, Wikimedia Commons
America exported numerous delicious invasive species. In addition to crayfish, bullfrogs and lobsters, largemouth bass have invaded freshwater ecosystems around the world. Although the feisty fish make good sport for anglers and a tasty dinner, they have also decimated native ecosystems. People intentionally released the fish to fuel sport fishing. Others escaped from fish farms.
Largemouth bass now swim the waterways of every continent except Antarctica and Australia. They eat anything that fits in their mouth and can out compete other top predator fish. Spines on the bass' back makes them dangerous prey for other large fish.
A rosy wolf snail, Euglandina rosea, from Kauai, Hawaii.Dylan Parker/Flickr/Wikimedia Commons
It's a snail-eat-snail world. The rosy wolf snail devours other snails, shell and all. Humans tried to harness the hunger of the wolf snail to control another invasive species, the giant African land snail. However, as with the crawdad, this solution to a pest problem turned into an even greater ecological disaster.
The wolf snail hails from the southeastern United States and humans helped it spread globally. The voracious wolf snail decimated other mollusks in its path. In the Pacific, the wolf snail wiped out all but five of 61 snail species that once lived on the Society Islands, according to CAB International. The International Union for the Conservation of Nature declared the wolf snail one of the 100 worse invasive species and condemned the use of the wolf snail as a pest control agent.
A Colorado beetle eating a potato plant. Petko Danov/Getty Images
Most invasive species escape into the wild and alter native ecosystems. But the Colorado potato beetle attacks agriculture, particularly the leaves of potato and tomato plants.
In the 19th century, the beetle spread from southwestern North America as Americans started planting potatoes on the newly conquered continent. By early in the 20th century, the beetle had colonized farms in Europe and Asia.
The beetles dramatically reduce potato production if they aren't controlled with insecticides. However, the insects are adept at evolving tolerances to pesticides. The beetles developed resistance to more than 25 insecticides, starting with DDT in the 1950s.