Animals Pets 7 Exotic Pets That Became an Invasive Species By Michael d'Estries Writer State University of New York at Geneseo Michael d’Estries has been writing about science, culture, space and sustainability since 2005. His writing has appeared on Business Insider, CNN, and Forbes. our editorial process Michael d'Estries Updated October 23, 2019 Mark Kostich / Getty Images Share Twitter Pinterest Email Animals Wildlife Pets Animal Rights Endangered Species Have you ever thought of releasing an exotic pet into the wild? You're not alone. As state officials across the United States have discovered, some former pets have turned into massive invasive species, displacing and out-competing native flora and fauna. The following are just seven of the invasive species that were released by humans into the wild with disastrous ramifications. 1 of 7 Goldfish Photo: Snapshot from video Goldfish, those innocent pets of childhood once relegated to the fish bowl, are now taking over fresh waterways around the world. A member of the carp family, the species can grow to between 16 to 19 inches and weigh more than 2 pounds in the wild. Due to a high rate of reproduction and a lack of natural predators, goldfish easily disrupt ecosystems by consuming resources, eating eggs of native species and spreading disease. Impact examples include the recent drainage of an artificial stream in Utah to remove thousands of illegally dumped goldfish, a lake under threat from a booming population in Colorado and giant versions of the species running amok in Australia. The species is so prevalent in the warm, shallow waters of western Lake Erie that it's now a commercial catch with over 113,800 pounds of goldfish netted in 2015. 2 of 7 Argentine tegus Photo: Bjørn Christian Tørrissen/WikiMedia In 2009, as part of campaign to trap invasive species in South Florida, biologists captured 13 Argentine tegus. In 2015, they caught more than 700. The black and white lizard, native to South America, is commonly found in pet stores throughout the United States. Because they can grow in excess of 5 feet, owners sometimes release them into Florida's copious swamps and waterways. In the wild, they can survive for 15 to 20 years, gorging themselves on a diet of fruits, eggs and small mammals. What they find, they eat, and they may attack humans, too. In addition, they can survive temperatures as low as 35 degrees and have the ability to reproduce extremely quickly; a nest can contain around 35 eggs. "There is no debate about tegus," biologist Frank Mazzotti told the Orlando Sentinel. "All of Florida is at risk." Tegus are hitting the Tampa Bay area especially hard, and the Fish & Wildlife Commission is concerned, but there is no organized effort to get rid of the creature (unlike the invasive Burmese pythons). 3 of 7 Snakehead Photo: Brian Gratwicke [CC BY 2.0]/Wikimedia Commons Snakehead, native to parts of Asia and Africa, are quickly making themselves at home in North America. Discovered in Maryland pond in 2002 (pdf), the species has since been spotted in states such as Virginia, California, New York and Maine. Not only can they grow over 3 feet long and weigh more than 12 pounds, but they also have the unique ability to migrate short distances over land thanks to specialized gills. Some have been known to flop on wet land to neighboring bodies of water. The species' population is difficult to control as it lacks natural predators and its females are capable of releasing more than 75,000 eggs each year. 4 of 7 Burmese python Photo: U.S. Fish and Wildlife Service Headquarters/WikiMedia With population estimates as high as 300,000 in southern Florida, the Burmese python has gone from exotic pet to established apex predator is as little as 30 years. With an average length of 12 to 13 feet, pythons have few predators besides alligators and humans. In regions with established populations, sightings of raccoons, foxes, bobcats and other mammals declined between 88 and 100 percent. Even birds and deer have been found inside pythons killed by park officials. "Burmese pythons are cracking the code on the Southwest Florida habitat, learning how to survive and breed locally," the Conservancy of Southwest Florida said in a press release. A hunt earlier this year removed several dozen snakes from the wild, including one measuring more than 16 feet long. 5 of 7 Starling Photo: Charlesjsharp/sharpphotography/Wikimedia Commons In 1890, a New Yorker named Eugene Schieffelin acted on a plan to introduce in North America every bird mentioned in the works of the playwright William Shakespeare. After importing 60 starlings from Europe, he subsequently released them in Central Park. Those original 60 have since turned into a population of more than 200 million. While they may have hypnotic murmuration displays, Starlings have become a major invasive pest. Capable of devouring entire fields of wheat, they're also prone to kicking other birds out of their nests, killing eggs and fledglings in the process. 6 of 7 Red-eared slider Photo: Monika Korzeniec/WikiMedia Originating from the warmer climates of the southeastern U.S., red-eared sliders have since proliferated around the world due to their popularity as pets. Feral populations now exist in areas such as Israel, Guam, Australia and the Caribbean Islands. In Japan, a recent study estimated that red-eared sliders now outnumber native turtle species 8-to-1, consuming up to 320 tons of water weeds each week in a single region of the country. Because of their larger body sizes (growing up to 1 foot in the wild) and higher reproductive rates, red-eared sliders quickly dominate native species, out-competing them for food and basking spots. "Red-eared sliders are on the list of the 100 most invasive species in the world," Allison Begley of Fish, Wildlife and Parks told Independence Record. "They're omnivores. They eat anything, and they adapt to any habitat." 7 of 7 Pacu Photo: Nisamanee wanmoon/WikiMedia Notable for its uncanny mouth of human-like teeth, the pacu is a popular pet store fish that has made its way into the lakes, ponds and creeks of at least 27 U.S. states. While popular as juveniles, this South American native can grow aggressively, prompting owners to free them into local waterways. In the wild, the pacu can grow to more than 3 feet long and weigh up to 44 pounds. Their teeth, while humanoid in appearance, are used for grinding down tree nuts that fall into local waters. While most pacu do not survive winter conditions in the U.S., there's a fear that a sizable population could take hold in warmer regions, leading to yet-another tip of the scales over native species for resources and habitat.