List of Exotic Pets Released into the Wild
About this list
While there are many introduced species in the United States, not all can be considered invasive. The term 'invasive' describes a non-indigenous (alien) species that becomes abundant and established as a self-sustaining population within the environment. Invasive species often have a negative impact on the ecosystem, human health, or pose a threat to agriculture.
When I first started this list months ago, I thought this would be an easy list to create based on this Wikipedia article listing a relatively small number of species. However, upon further research I discovered many other animal species that are described as 'invasive' by several research sites, often abandoning the above criteria. I also stumbled upon conflicting research (some animals are established but listed as not invasive, like budgerigars).
Therefore, it became difficult to discern which species should be listed here, so to avoid any confusion, I listed more species than necessary to be safe. Not all species listed have confirmed impacts on the environments, and a few may be isolated to certain locales and are just assumed to be reproducing and spreading.
An **asterix** denotes species that are a significant invasive species that have strong negative impacts or are highly established and unable to be irradiated.
Only exotic animals (non-domesticated) that have originated entirely or partially from any pet trade situation are listed here. For some of the animals, mainly those in the fish and invertebrate category, if the information regarding their introduction is not available I 'assume' it was a pet trade escape or release if they are common in the pet trade unless it is stated otherwise.
Keep in mind that many invasive animals (and plants, of course) originate from other sources such as the live food market, intentional introduction, escapes (of domesticated animals such as cats and waterfowl) and travel hitchhikers that could double or triple the numbers of the animals listed here. The animals on this list have varying effects on the environment and with some, none have been observed.
- African Clawed frog (Xenopus laevis)- A keystone specimen in scientific study (developmental, cell, and molecular biology), but also prominent in the pet trade. African clawed frog populations have been reported in 11 states, including Arizona, California, Colorado, Florida, Louisiana, Nevada, New Mexico, North Carolina, Virginia, Wisconsin, and Wyoming. It may threaten native frogs and predate on an endangered species of frog.
- Australian Green Tree frog (Pachymedusa dacnicolor)- Introduced to two regions in Florida which is assumed to come from the pet trade. Ecological impact is unknown.
- **Bull frog** (Lithobates catesbeianus)- Native to central and eastern United States but introduced to the Western U.S. in the 1900s from trout stockings. Also introduced through the aquarium trade and for sport and pest control. Competes with and preys on native species.
- Cuban Tree Frog (Osteopilus septentrionalis) - Consumes native tree frogs and lizards in Florida. Introduced in 1931, and the populations are expanding.
- Oriental Fire-bellied Newt (Cynops orientalis)- In 2009, 5 specimens were collected in two different counties in Florida, which indicates they may be reproducing. This species is common in the pet trade. The impacts of their introduction are unknown, though this species is mildly poisonous and produces toxins from its skin.
Three-toed Amphiuma (Amphiuma tridactylum)- This species is native to the Gulf Coast region, and its been introduced to Florida where several specimens were collected in Broward County, Florida. Due to this it is assumed they are established. Many are sold from Louisiana as pets, and hundreds are used in laboratory studies. Most are taken as off-catch during crayfish trapping. Impact of introduction is unknown.
Due to warmer climates, exotic bird introductions typically in the warmer regions of Florida, California, Texas, and Hawai'i. The monk parakeet is one species that has spread to several states including some in the Northeast. Many invasive birds have these traits in common: migratory habits, broad diet and habitat niches, behavioral flexibility and fore brain size.
- Alopochen aegyptiaca (Egyptian Goose)- Rarely breeds successfully and not listed as established in Florida (but present from continued escapes from private collections), however it is stated here that there are growing feral populations in Texas.
- Amazona viridigenalis (Red-crowned parrot) Introduced to Florida and California. Endangered in the wild, but status as an invasive in the U.S. is unknown.
- Acridotheres tristis (Indian Myna)- Flocks of the common myna are known to damage fruit crops and carry some diseases (Psittacosis, Ornithosis, Salmonellosis, ect.) and parasites (owl fleas, biting lice, ect.). Introduced to Hawaii and the Florida Everglades. They have been reported to attack purple martins.
- Brotogeris versicolurus (White-winged parakeet)- Non-native range is limited to Florida, California, and Puerto Rico.
- Carpodacus mexicanus (House Finch)- Native to Western United States and Mexico, the birds were illegally sold as "Hollywood finches" in the 1940s and released by the unscrupulous dealers to avoid prosecution under the Migratory Bird Treaty Act of 1918. These birds are highly adaptable to urban and suburban environments, and may become a nuisance (also in their native range) to agriculture.
- Cygnus olor (Mute swan)- Several states east of Minnesota have populations of as much as thousands of birds. The populations are increasing. Mute swans have escaped captivity or have been intentionally introduced to protect ponds from geese and for ornamental purposes.
- Icterus pectoralis (Spot-breasted Oriole)- Established in Florida
- Melopsittacus undulatus (Budgerigar)- These birds are extremely popular as pets, and breeding populations have become established in Florida since the 1930s, mostly along the Gulf Coast. However, breeding is short-lived, and some populations regularly die off due to freezes.
- **Myiopsitta monachus** (Monk parakeet)- Very popular in the pet trade, and the most famous invasive species of parrot. It is considered to be a significant agricultural pest that builds large nests on telephone poles and transmission towers, causing some to short. Monk parakeets can cause costly damage to electrical utilities. They have been introduced to the eastern United States, as well as several other countries.
- Nandayus nenday (Black-hooded Parakeet)- Native to South America, there are established, self-sustaining populations in Los Angeles, and several locations in Florida (St. Petersburg, Broward County, and Miami-Dade County).
- Psittacula krameri (Rose-ringed parakeet)- A more prominent invader in Europe and Australia, where it causes agricultural damage. It has also been introduced to the U.S.
- **Porphyrio porphyrio** (Purple Swamp Hen)- A recent introduction to Florida with ecological similarity to other natives. It is currently poorly studied, but is known to eat bird eggs and nestlings. It is also territorial which impacts natives.
- Streptopelia decaocto (Eurasian collared-dove)- Introduction to the U.S. (and other nations) may have resulted from a pet breeder in Nassau in 1974. It may compete with native birds and potentially spread some diseases such as West Nile virus.
Other birds, unconfirmed
- "Members of the parrot family carry Newcastle disease, identified in 1971, which can infect native songbirds, game birds, domestic chickens and turkeys, and other exotic bird species. The native bird species can be infected by smuggled exotic birds and birds not properly quarantined that are released into the wild. This species also breeds in cavities which might limit the number available to native cavity nesters."
- Ara severa (Chestnut-fronted Macaw)- Potentially established
- Gracula religiosa Linnaeus (Hill Mya)- Potentially established
Fish (Florida established)
- Astronotus ocellatus (Oscar)- Established in Southern Florida, Hawaii, and Puerto Rico. Introductions resulted from deliberate stockings from an aquarium fish farm for recreational purposes. Other failed introductions have likely occurred with pet releases. Ecological impact is unknown.
- Cichlasoma bimaculatum (Black acara)- Introduced to Florida through aquarium release/ escape. No significant impact on native fishes.
- Cichlasoma urophthalmus (Mayan cichlid)- Introduced to Florida including the Everglades. Nest predation of native centrarchids by Mayan cichlids has been observed in the Everglades National Park. Presence of Mayan cichlids may affect prey behavior. They are a potential vector of diseases and parasites. Its introduction into Florida may have been associated with the ornamental fish trade and by fishermen.
- Clarias batrachus (Walking catfish)- In the early 1960s, the walking catfish was imported to Florida from Thailand for the aquarium trade. In 1967, the state of Florida banned the importation and possession of walking catfish. However, this led to another release of the fish into the wild. By 1978, the walking catfish had spread to 20 counties in the southern half of the peninsula. They are established in the Everglades National Park and in Big Cypress National Preserve. They have also been collected in California, Connecticut, Massachusetts, Nevada and Arizona.
- Hypostomus plecostomus (common pleco or suckermouth catfish)- Breeding populations are present in Florida and Texas. Sometimes they are intentionally released to control algae. Local indigenous species can be out-competed and reduced due to this. These fish can survive out of water for 30 hours.
- Monopterus albus (Asian swamp eel)- imported as a food source and for the aquarium trade. In Florida and Georgia, the introduction of M. albus is likely due to an aquarium release or a fish farm escape or release. They may compete with native species.
- Pterygoplichthys multiradiatus (Orinoco Sailfin Catfish )- Most introduced populations are believed to be the result of pet release or aquaculture escape. Potential ecological effects include alteration of bank structure and erosion, disruption of aquatic food chains, competition with native species, mortality of endangered shore birds, changes in aquatic plant communities, and damage to fishing gear and industry. Established in Florida and Hawaii.
Fish (other states)
- Cephalopholis argus (Peacock hind)- Established in Hawaii. It is a dominant near-shore coral reef predator around the main islands. Likely alters community structure. Introduced through stocking as food/game fish, but intentional release from the aquarium trade is also probable
- Belonesox belizanus (Top minnow)- Escapees from an ornamental fish farm has resulted in a population in Hillsborough County in 1997. Introduced to Texas probably from aquarium release, although they have now been extirpated in these locations (established populations in Florida resulted from medical research release). This piscivore competes with native fish.
- Cyprinella lutrensis (red shiner)- The introduction into the Yadkin drainage, North Carolina, was possibly the result of an aquarium release (other populations in other areas originate from bait bucket releases). The red shiner is very aggressive and where introduced may dilute the gene pools of native species.
- **Channa gachua** (dwarf snakehead, and other snakehead species)- Snakeheads are prohibited in many states due to their aggressive tendencies as an invasive. Some infestations have been irradiated. Northern Snakeheads are established in Arkansas, New York, and Pennsylvania. While pet release may have contributed to their populations, snakeheads are more prominently sold in live Asian fish markets. One Maryland man released the fish after he no longer needed them for medicinal purposes. Snakeheads are predatory and prey on endangered aquatic wildlife. When wet, they can survive on land for up to 4 days and can migrate to other bodies of water.
- Misgurnus anguillicaudatus (oriental weatherfish)- Common in the aquarium and live bait trade. Established populations are located in the Shiawassee River and Lake Michigan; also California, Florida, Hawaii, Idaho, Illinois, Michigan, New Jersey, New York, Oregon, and Washington, and possibly in Louisiana. Status is unkonwn in Tennessee, North Carolina, and Maryland. One experiment shows the oriental weatherfish may significantly reduce macro-invertebrate abundance and increase turbidity and nitrogen levels in standing water.
- **Oreochromis mossambicus (Mozambique Tilapia)**- Most introductions have been as a result of aquatic plant and mosquito control by the state. They have also been introduced as bait fish, food, and aquarium releases. They are established in 7 states including New York, Hawaii, Florida, and Texas.
- Piaractus brachypomus (red-bellied pacu)- Aquarium releases are indicated, although some Florida and Georgia records may have resulted from fish farm escapes. Reported from 19 states: Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Kentucky, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, New York, North Carolina, Oregon, Texas, and Virginia. Impact of introduction is unknown.
- **Pterois volitans** (Lion fish)- A prolific invasive species, established throughout Florida's waters, and also has been known to migrate to northern regions (as far as the Long Island Sound). Their predation on native ecologically important fish may diminish their populations, as well as impact other predators.
Other fish present but not established or no data
Banded cichlid, Arabian angel, Sohal surgeonfish, convict cichlid, armoured catfish, clown knifefish, panther grouper, yellowbelly cichlid, brook stickleback, lined topminnow, redstriped eartheater, African jewelfish, Red Sea bannerfish, small-scaled pacu, orbiculate batfish, firemouth cichlid, green swordtail, southern platyfish, variable platyfish
- **African land snail** (Achatina fulica Férussac, 1821)- Introduced through the pet trade, as well as for human consumption, the African land snail reproduces rapidly and affects agriculture, ecosystems, and human health. Has been listed as one of the world's top 100 invasive species.
- Caribbean land snail (Cepolis varians)- Florida Everglades
- Giant ramshorn snail (Marisa cornuarietis Linnaeus, 1758)- Southern Florida
- Red-rim melania (Melanoides tuberculatus Muller, 1774)- Present in AZ, CA, FL, HI, ID, LA, MN, NC, NV, OR, SD, TX, UT, and WY. Competes with native snails. Introduced accidentally from the aquarium trade in the 1930s.
- Spiketop applesnail (Pomacea bridgesi Reeve, 1856)- Probably introduced in the 1950s, present central north Florida. Called the golden apple snail in the aquarium trade.
- Channeled apple snail (Pomacea canaliculata Lamarck)- California and Hawaii.
- Island applesnail Pomacea insularum (d'Orbigny, 1839)- Potential threat to Florida ecosystem.
- Boring clam (Tridacna crocea Lamarck)- Florida Everglades
- Small giant clam (Tridacna maxima Roding)- Florida
- African redhead agama (Agama agama)- Believed to have been released or escaped during hurricane Andrew. They are expanding and have been established in two counties in Florida for at least 10 years, and less than 10 years in 3. The impact they may have is unknown, however they are carnivorous and prey on smaller animals.
- Ashy Gecko - (Sphaerodactylus elegans)- This Cuban species is restricted to the lower FL Keys, where it was once common but is now declining, possibly due to the introduction of the predaceous tropical house gecko (Hemidactylus mabouia). There are no threats to natives known.
- Brown basilisk (Basiliscus vittatus)- This species, sometimes known as the 'Jesus lizard' for its ability to run on top of water with great speed, was introduced to South Florida in 1976. Populations are confirmed breeding and apparently self-sustaining for 10 or more consecutive years. They are expanding, with no threats known to natives, however they prey on smaller vertebrates.
- Butterfly lizard (Leiolepis belliana belliana)- The threats to natives for this agamid species is listed as "probably none", as it is an insectivore. Their populations are breeding successfully in 10 counties.The Miami populations originated from a nearby tropical fish dealer. This species has been established since 1992.
- Burmese Python (Python molurus) - One of the largest snakes in the world and responsible for considerable attention toward the invasive species exotic pet trade problem. They are mainly established in the Everglades, but individuals have been found near Naples, suggesting their their population might be moving Northwest. Pythons observed outside of FL are escaped pets, but not established. It is likely that the established population escaped from a breeding facility after hurricane Andrew. Pet releases are also implicated. Being top level predators and only falling prey to alligators and humans, they are considered a profound environmental hazard.
- Common Boa (Boa constrictor imperator)- Common boas are a threat to vertebrates at their adult size. There is also concern that they may out compete smaller native boas in Puerto Rico. Many boa species carry ticks which could be transmitted to domesticated livestock.
- Common caiman- (Caiman crocodilus)- Caimans, due to their smaller adult size, are popular 'replacements' for pet alligators and the demand for them rose after alligators were banned in many states. It is believed that most non-indigenous occurrences of this species are due to pet releases. In Dade County in Florida, the destruction of a holding facility in 1992 for reptiles due to Hurricane Andrew accounts for another hypothesis for their introduction. Caimans are established in Florida and attempts at eradicating them failed. They may impact the ecosystem due to their carnivorous nature and introducing parasites.
- Common house gecko (Hemidactylus frenatus) - Commonly imported in the pet trade, and may be established around reptile dealerships in 4 counties. No threats to natives known. Introduced in 1979.
Common snapping turtle (Chelydra serpentina)- Indigenous to the United States, but introduced and may or may not be established in Oregon, Washington, Utah, Nevada, Arizona, and California. It is hypothesized that their presence is due to negligent pet owners. All snapping turtles are voracious predators and pose a threat to smaller native animals.
- Giant Ameiva (Ameiva ameiva) Presumed to have escaped from the pet trade, these somewhat larger lizards prey on smaller vertebrates. They are common in Dade County, Deerfield Beach, Broward County in Florida. They are confirmed breeding and self-sustaining for over 10 years. Statewide trend is expanding.
Giant Day Gecko (Phelsuma madagascariensis grandis)- While this species has been released in other parts of Florida, the only population that appears to be established is in the Florida Keys. There are no known threats to natives. First appeared in the 1990s.
- Giant Whiptail (Cnemidophorus motagua) - A large teiid lizard, one thriving population was established in Miami in 1995, assumed to be a deliberate release. In 2004, another population was discovered in the Everglades. There are no known threats to natives but it is assumed they will feed on smaller lizards.
- **Green iguana** (Iguana iguana)- Green iguanas are extremely popular in the pet reptile trade, and escapes/releases have led to their expanding populations. However, they are sensitive to the cold and only survive in South Florida. Threats to natives are unknown, however they have provided annoyances to humans and their droppings may carry salmonella.
- Many-lined Grass Skink (Mabuya multifasciata)- This species is restricted to a small botanical garden in Dade county, where they are suspected to have originated from the pet trade. Threats to natives are unknown, however they may compete for food with native lizards and they can consume other vertebrates.
- Mediterranean Gecko (Hemidactylus turcicus)- This species has been introduced to many states and countries. It breeds rapidly, is resistant to pesticides, and has expanding populations. Despite this, it is not expected to have any significant impacts in the environment. It is firmly established in Florida, Texas, California, Louisiana, Alabama, Texas, and may continue to expand north.
- **Nile Monitor** (Varanus niloticus)- As the second most commonly sold African monitor species in the U.S., the Nile monitor is a voracious predator and has been confirmed breeding only in Cape Coral, Lee County. They consume birds, mammals, frogs, lizards, and can dig up eggs of sea turtles and alligators.
- (Cnemidophorus lemniscatus)- Presently confined in Florida to 2 or 3 warehouse complexes in Dade County, originating from pet trade escapes/releases. There are no threats to natives known.
- Red-eared slider (Trachemys scripta elegans)- Indigenous to midwestern states in the U.S., occurs as a non-native species in many locales, including New York, North Carolina, Florida, Nebraska, Arizona, Hawaii, and California. Escapes and release from the pet trade are considered to be the main means of introduction, and many of the populations are thriving, being adaptable to many climates. They have a speculated but unconfirmed impact on the environment.
- Red-sided Curlytail Lizard (Leiocephalus carinatus armouri)- Intentionally released in the 1940s in Palm Beach to rid sugar cane of pests, but speculation of pet trade releases is also implicated. They have an unknown impact and are said to be expanding in Florida.
- Spiny softshell turtle(Apalone spinifera)- Native to many regions in the U.S.,the spiny softshells were introduced into Florida and France due to the pet trade. Ecological impact is unknown.
- Texas Horned Lizard (Phrynosoma cornutum)- Native to the Great Plains, this species was introduced to Florida when it was popular in the pet trade. This is no longer the case because they require a diet of mostly ants. It has an unknown stateside trend and current status of breeding.
- Tokay Gecko (Gekko gecko)- This large lizard is widely sold in the pet trade and sometimes released to control cockroaches. It can potentially prey on bird nestlings and rodents. Their populations are expanding.
- Mexican Red-bellied Squirrel (Sciurus aureogaster)- Introduced and established in Elliott, Sand Key, Miami-Dade County, Florida. Released by owner.
- Some monkey populations exist in Florida due to escapes from zoos/exhibitors (not really an exotic pet). They are the vervet monkey (Chlorocebus aethiops) rhesus maquaue (Macaca mulatta) and squirrel monkey (Saimiri sciureus).
- Prairie Dog (Cynomys ludovicianus) escaped from owners
- Gambian Pouch Rat (Cricetomys gambianus) escaped from breeder
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