Under the Radar: Nonnative Species You Never Knew Were Nonnative

​For this chapter I will be focusing on five species, which are so common in some areas that they are often not thought of being, and invasive species. Animals and plants alike, some species are so common that they are often overlooked as invaders. This is especially common for plants that we see used for landscaping purposes or see in the wild frequently; an animals that we see every day on farms, kept as pets, or commercialized!

​The American Bull Frog (Rana catesbeiana)
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This large American frog is Native to the eastern United States. This frog is found in close proximity to lakes and ponds, as well as slower moving bodies of fresh water. When they breed they can produce over 10,000 eggs! Once transformed into tadpoles, the larvae can take between four months to three years to change into their adult frog forms. Theses frogs were first thought to have been introduced through fish stocking of ponds, but other modes of introduction including release and human-facilitated movements of the frogs are also thought to play a role. The impact these frogs have on the areas where they have been introduced include out competeing native frog species, altering the aquatic structure of lakes due to the larvae consuming copious amounts of algae, they are known to eat birds, rodents, other frogs, snakes, turtles, lizards, and even bats. They have been introduced to 20 other states, including: Arizona, Hawaii, Colorado, and Nebraska!

Invasive sightings of water hyacinth in the United States. Provided by EDDMaps

Water hyacinth in bloom/ Photo from: Full Service Aquatics

Feral Pigs (Sus scrofa)
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Pigs have been domesticate for centuries, and were imported into the USA intentionally from Eurasia as a source of food. Since their introduction for domestic purposes, however, pigs have escaped or been intentionally released. Feral pigs are present in 35 states, and their numbers have been estimated to be over 5 million individuals. These pigs pose a threat to native environments by introducing and spreading diseases, damaging the environment and personal properties, a risk to livestock health and to human health. Pigs are very adaptable and are encroaching on very urbanized areas, making them a threat to homeowners and businesses by rooting up lawns, golf courses, and park lands. It is estimated that feral pigs cost over $1.5 billion in damages and control each year. Their wallowing behavior cause damage to riverbanks (erosion), and private and public properties. Pigs are also known to destroy crops including corn, watermelon, spinach, hay, and peanuts, as well as prey on young livestock and small animals including ground nesting birds. They can carry and transmit over 30 diseases, and 37 parasites, which can be transmitted to humans, pets, wildlife, and livestock.

The antive (green) and invasive (red) ranges of he American bull frog - provided by https://nas.er.usgs.gov/queries/factsheet.aspx?speciesid=71

American Bullfrog /MDC Staff / Photo by MDC Staff, courtesy Missouri Department of Conservation.

​Water Hyacinth (Eichhornia crassipes)
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Water hyacinth is an aquatic plant which forms free-floating mats on the water’s surface. They have anywhere from 8 to 25 flowers bloom per branch, and the flowers are blue-lavender in color with yellow patches in the uppermost petal. They are native to the Amazon River basin of South America, and was introduced to the United States in 1884 and can now be found in 32 states. This plant can flourish in many aquatic habitats including lakes, ponds, rivers, and wetland areas. It is a popular water garden plant because of the fact it can withstand water fluctuations, variable water flow rates, acidity, and low levels of nutrients. This plant is a threat to ecosystems by altering native vegetation and fish communities through reducing light penetration and dissolved oxygen levels in the water. It also makes water travel on rivers and water ways, as well as clogs canals and water intake pumps.

Distribution of feral swine in the USA in 2017. (Map provided by https://www.aphis.usda.gov/wildlife_damage/feral_swine/images/2017-feral-swine-distribution-map-county.jpg)

A walking catfish (Photo from: http://www.tbo.com/brandon/walking-catfish-common-during-heavy-tampa-area-storms-20150812/)

Invasive range of the walking catfish (Map provided by http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Clarius_batrachus.html)

Domestic Cats (Felis catus)
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The domestic cat is one of the most common pet kept in the United States. The domestic cat is derived from breeding wild cats (Felis silvestris) over 10,000 years ago. The domestic cat is now considered a distinct species, and as a domestic animal they have no native range and are considered a nonnative, invasive species. Feral cats can reproduce prolifically, and can be sexually maturfe as early as six month in age; reproducing multiple times a year. The cat is a highly skilled hunter of vertebrate species, as all cats are carnivorous, and even when well fed they will continue to hunt for prey. This desire to hunt makes them a constant threat to all wildlife species wherever they live or are permitted to be outdoors. There is sever ecological impacts caused by free ranging domestic cats, and they are responsible for the extinction of numerous species of mammals, reptiles, and at least 33 birds across the globe. It is especially harmful when cat colonies are sustained by humans. In areas where rare species are present, even if well fed the cats will continue to prey upon the rare animal until it has gone extinct. Cats are also vectors of diseases including zoonoses – disease that can be transmitted to humans – including rabies, toxoplasmosis, bartonellosis, and salmonella. Currently, there are many programs in place to spay and neuter feral cats, however these programs do not reduce cat populations. The TNR (trap-neuter-release) programs simply release the cat back into the environment, even if they are sterilized and vaccinated, the cats continue to harm native wildlife and people.

Walking Catfish (Clarias batrachus)
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Walking catfish are scaless fish with flat, wide heads and a body that tapers towards the tail. This fish has spines on each of its pectoral fins, which it uses to “walk” across land between bodies of water. These catfish are native to Southern Asia, including the Philippines, Thailand, Myanmar, and Sri Lanka. In their native range the catfish are a common food item that can e bought for a relatively cheap price. They are used in many dishes, and is a delicacy in Assam, a state of India. They can currently be found in 7 states, and have established wild populations in Florida. They were likely introduced by humans through the pet trade and international trade for food. These fish pose a threat to aquaculture farms, native catfish due to them carrying the disease enteric septicemia, and to native fish species as they are voracious opportunistic feeders. The walking catfish is an omnivore, and its diet consisted of plants, detritus, invertebrates including mollusks, and small vertebrate prey items. In Florida the catfish are especially devastating in wetland pools because they quickly dominate the small water bodies. Since they have been deemed a menace to native species the walking catfish is illegal to possess or transport live without state and federal permits.

A feral cat with 107 Short-tailed bats in its stomach (the short tailed bat is only found in New Zealand, and feral cats are the leading cause of the decline in their populations) (Photo from: )

A feral cat with a dead Brush-tailed Phascogale (a vulnerable species in Australia) (Photo from: http://georgesoutdoornews.bangordailynews.com/2015/07/25/environmental-issues/two-million-cats-to-be-shot-and-poisoned/)

A feral cat with a freshly killed bird (Photo from: https://now.tufts.edu/articles/cat-eat-bird-world)

For More information:
Bull Frog
https://nas.er.usgs.gov/queries/factsheet.aspx?speciesid=71
https://www.fws.gov/fisheries/ans/erss/highrisk/ERSS-Lithobates-catesbeianus-final-February2018.pdf
https://www.fs.usda.gov/r4
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Water hyacinth
https://www.invasivespeciesinfo.gov/aquatics/waterhyacinth.shtml
http://www.tsusinvasives.org/home/database/eichhornia-crassipes
https://www.se-eppc.org/manual/EICR.html

Feral Pig
https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/operational-activities/feral-swine
https://www.invasivespeciesinfo.gov/animals/wildboar.shtml
http://www.environment.gov.au/biodiversity/invasive-species/publications/factsheet-feral-pig-sus-scrofa
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Walking Catfish
https://www.floridamuseum.ufl.edu/science/five-facts-walking-catfish-in-florida/
http://myfwc.com/wildlifehabitats/profiles/freshwater/nonnatives/walking-catfish/
http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Clarius_batrachus.html

Feral Cat
http://wildlife.org/wp-content/uploads/2014/05/Feral-Cats.pdf
https://abcbirds.org/threat/cats-and-other-invasives/
http://www.environment.gov.au/biodiversity/invasive-species/publications/factsheet-feral-cat-felis-catus

About the Author: Jenna is a graduate student at the University of Florida. Currently she is studying Wildlife Ecology and Conservation while working in south Florida to manage invasive animals. Jenna primarily works with the Argentine Black and White Tegu and other invasive lizards.​