One of the most abundant invasive species in the United States is the nutria, a rodent introduced to the eastern United States. This mammal is native to South America and lives in wetland ecosystems. Since nutria eat the roots of marsh grasses and dig large burrows near rivers, wetland ecosystems in the United States have experienced soil erosion and tidal flooding throughout the 20th century.
Another disruptive mammals is the feral pig, which has a growing population in the Hawaiian Islands. Feral pigs create mud wallows and feast on the pulp of the state's tree fern. Also, these mammals have introduced avian malaria and birdpox since feral pigs inadvertently create mosquito populations.
Florida has 14 invasive bird species that have created established populations within the Sunshine State. One of the most prolific introduced birds in Florida, the monk parakeet, grows up to 1 foot long. Two closely related birds to the monk parakeet – both introduced to Florida – are the white-winged parakeet and yellow-chevroned parakeet. The monk parakeet has also established populations in Texas, New York and Illinois. Monk parakeets build their own nests from sticks, which make them huge competitors for nesting in tree cavities. However, monk parakeets have had a significant impact on urban environments since they like to nest on houses and buildings. Also, these birds are highly social, so when large groups of monk parakeets may nest on a house at the same time.
South Florida is also home to invasive reptiles such as the green iguana and Burmese python. Both reptiles are native to the tropical jungles of Central America and South America. Green iguanas and Burmese pythons were introduced to South Florida as pets, but escaped captivity to start populations. Green iguanas have damaged the South Florida wetlands ecosystems since they eat fauna and vegetation at a rapid rate, which does not give the fauna a chance to grow again.
The ecosytems of Guam have suffered from the introduction of brown tree snakes in the mid-20th century. The brown tree snake's introduction has resulted in depleted populations of native small mammals and birds. Also, this snake is venomous and envenomated the island's human population.
The sea lamprey is an invasive species of the Great Lakes region, where it first appeared in Lake Ontario during the 19th century. This fish is native to New York's Finger Lakes and one theory suggests they accessed the Great Lakes after the building of the Erie Canal. Sea lamprey are parasitic and prey on commercially viable fish such as bass and trout. As a result, native fish in the Great Lakes region have experienced a population decline since the 1950s.
Another introduced fish is the blue tilapia. This fish's range in the United States extends from Florida to Texas. The presence of blue tilapia has affected the populations of largemouth bass by preying on the bass' larvae.