Throughout natural history, humans have selected a number of plant and animal species as optimal to grow better and more available food. These plants and animals are brought from other environments and establish themselves in their new location. Animals like cows fit the definition of an introduced species: a nonnative species intentionally brought to serve a specified purpose or unintentionally introduced via faulty management. Cows were brought to North America as a food source and are continued to be used to this day. This intentional purpose is contrasted with other species, notably plants, that are nonnative to the US and can grow out of control. When a nonnative species enters a new ecosystem, a variety of results can occur; it does not last beyond that initial introduction or rapidly grows as it may not have any natural predator in the new ecosystem.
Another term for an introduced species is an exotic or invasive species. Invasive species is the buzzword that circulates across locations in which a nonnative species begins to take over an area and outcompete the native ones. Throughout the US, the issue of invasive species has been growing over the last few centuries. Recent studies are now showing the vast impact these new animals may have on local ecosystems. Exotic animals fit the same description of an invasive one, but these animals have been brought over for an intentional purpose: pets. Both intentionally and unintentionally introduced species still share similar detrimental effects on local ecosystems.
As more and more invasive species find their way to US soil, the impact they have on the environment and native species continue to expand. Biological and ecological threats to native species have led to more significant population declines of the native animals. There are a number of solutions that have been deemed most effective to combat the growing numbers of invasive species. However, most of these techniques to eradicate invasive species come at the cost of animal welfare. The stigma associated with invasive species has seemingly trumped the understanding that animals deserve some level of respect through avoiding undue pain and suffering.
This paper will broadly define what an invasive species is and why they pose a threat to indigenous ecological communities. The next section will examine the legislation aimed at protecting native ecologies from invasives and how these laws are often silent on the animal welfare component. The paper then examines the threat invasive species pose through four species case studies. It concludes with suggestions on how current laws and conservation policies inadequately evaluate animal welfare in the US and how future proposals should include a cost-benefit analysis for native and invasive species.
Outlining the threats to animal welfare can be framed by looking at classes considered invasive, including mammals, birds, fish, and reptiles. Each category has specific examples of species that have threatened native ones. The variety of unethical treatments should be examined closely, noting that even though these invasive animals pose a significant threat and should be dealt with, there must be more ethical practices to still protect the animals from undue pain and suffering.
II. Background and History
An invasive species is a nonnative one introduced with or without intent: an invasive species can establish itself from either a single seed or a herd, growing rapidly due to a lack of competition or natural predation. For instance, the most well-known invasive species today are giant constrictor snakes found in the Florida Everglades. This includes both the boa constrictor and the Burmese python. The history of the Burmese python is relatively simple: the nonnative reptiles were introduced in the 1970s from Latin America. Without any known predators, the initial population grew, fueled by rapid gestation periods and high reproduction rates that led to a population explosion. More developed biology and anatomy enables Burmese python to consume massive amounts of food, including native species so, as populations grew, native species lost available food leading to lower populations. Fort Colling Science Center, Giant Constrictor Snakes in Florida: A Sizeable Research Challenge (July 3, 2016), available at https://www.usgs.gov/centers/fort-collins-science-center/science/giant-constrictor-snakes-florida-sizeable-research.
The simple history of Burmese python is consistent with many other species as well. As will be seen in Section III, the rapid growth of an invasive species is not reserved to only reptiles in southern Florida. The impact on native ecology also ranges depending on what the invasive species is and how it operates. The ecological damages due to invasive species can range from outcompeting native species leading to higher chance for extinction or choke native plants and waterways leading to severe economic damage. Focusing on animals, whether it is birds, mammals, fish, or reptiles like the boa, drops in native species can be directly attributed to invasive species. Animals that previously thrived in their natural habitat are continually threatened by growing populations of invasive species. Due to those growing threats to native species, public notion of how to deal with these nonnative animals have hit the point where the only goal is total eradication. The public understanding of invasive species leads a significant percentage of the population to believe these animals do not warrant the same standards of ethical treatment outlined by the AVMA.
III. Laws Addressing Invasive Species
Invasive species movement and proliferation after the introduction into native ecosystems span across state and national borders, making it more difficult for states and federal agencies to issue controls. Federal laws permit agencies to act on growing populations, issuing various guidelines for states and the public to follow as well as implementing its own control mechanisms. States will also create laws and control recommendations to the public to deal with the growing species. Federal and state laws work in conjunction with one another, but states will issue more precise laws targeted at the species found in those states.
A. Federal laws
One of the most important political actions that recognized the significance of invasive species came in 1999 with President Clinton signing Executive Order 13112. The Executive Order defined invasive species as an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health. In addition, “alien species” as any species, with respect to a particular ecosystem, including its seeds, eggs, spores, or other biological material capable of propagating that species, that is not native to that ecosystem. E.O. 13112 was passed in response to the acknowledgment of not only the extensive biological damage caused by invasive species, but also the economic harms to places like the Great Lakes where zebra mussels were severely damaging utility pipes feeding water to the bordering residents.
E.O. 13112 was not the only political action to be derived from the threats of invasive species. As far back as 1900, political orders have acknowledged the threat of invasive species and how national and state-level action is needed to curtail damage. Beyond E.O. 13112, other congressional actions include the following:
- The Lacey Act of 1900: the injurious species provisions found in 18 U.S.C. 42 state that the Secretary of the Interior will regulate the importation and movement of animal species through interstate commerce that may have a negative effect on humans or greater environmental interests.
- Nonindigenous Aquatic Nuisance Prevention and Control Act (1990): the primary goal of the Act was to prevent and control growing populations of the coastal inland waters, primarily the Great Lakes, by nonindigenous aquatic nuisance species including the zebra mussel. It also enabled a federal Task Force to work with local, state, tribal, and federal authorities and issue new laws that are more case-specific. 16 USCS 4701 - 4751.
- National Invasive Species Act of 1996 (1996): amending the Aquatic Nuisance Prevention and Control Act of 1990 to include additional controls of nonindigenous aquatic mussels, plants, and other nuisance species through the regulation of ballast water dumps from oceanic tankers. H.R.3217 - National Invasive Species Act of 1996, Available at https://www.congress.gov/bill/104th-congress/house-bill/3217.
- Asian Carp Prevention and Control Act (2010): an amendment to the Lacey Act that adds Asian Carp onto the injurious species list due to its impact on the Mississippi River, Great Lakes, and other inland waterways through the central states. See S.1421 , Asian Carp Prevention and Control Act, available at https://www.congress.gov/congressional-report/109th-congress/house-report/585/1.
B. State laws
Beyond the federal actions related to the control of invasive species, states themselves enact laws relative to the species affecting the local ecosystems. An analysis of specific animals and the applicable laws to them will be analyzed in Section III. Examples of how states control species can be seen in the Floridian Regulations of Burmese python. Some of the stricter laws include limiting the number of Burmese pythons that can be owned by an individual and breeding restrictions that must be overseen by state authorities. Beyond that, Florida has petitioned Congress to add Burmese python to the Lacey Act, similar to how the Asian Carp were added in an independent act in 2010. Florida Fish and Wildlife Conservation Commission, Regulations for Prohibited Snakes and Lizards, available at https://myfwc.com/wildlifehabitats/nonnatives/regulations/snakes-and-lizards/.
States experiencing some of the more significant harms due to invasive species will implement a variety of control mechanisms. In conjunction with federal agencies, state laws focus on the introduction of certain species, whether members of the public can own those species, and regulation of invasion pathways. States like Florida, Texas, and Michigan are examples of states that do not allow the general public to own species that will become invasive if introduced into the wild. (To see some of these laws, visit the Map of Private Exotic Ownership Laws). Exotic pets, like the black and white tegu and boas, are one of the major avenues for invasive species entering indigenous ecosystems. Beyond controlling direct introduction of these species, state and federal agencies provide additional controls to limit the movement of invasive species due to secondary events, like climate change and other factors forcing population movements. Cassandra Burdyshaw, Detailed Discussion of the Laws Concerning Invasive Species (2011).
III. Case Study: Modern Invasive Species and Damage
There are more than 6,500 nonnative species currently established in the United States, reaching as far south as Florida, as west as Hawaii, and as north as Alaska. United States Geological Survey, Invasive Species Program, available at https://www.usgs.gov/programs/invasive-species-program. Taken holistically, the economic and environmental damage caused by these plants and animals cause more damage than all natural disasters combined. Id. This section will analyze individual species across the four major classes of animals: mammals, fish, birds, and reptiles. Each class contains different threats to their respective environments, with the species studied here as the most prevalent or causing some of the more significant threats to the native species and environments.
A. Fish: the Asian carp
Compared to the wild boars, the Asian carp’s release into the United States is relatively new. In the 1970s, locals and scientists condoned the release of Asian carp to control nuisance algal blooms in wastewater treatment plants and aquaculture ponds. United States Geological Survey, What are Asian Carp?, available at https://www.usgs.gov/faqs/what-are-asian-carp. The freshwater fish, native to China, were also brought to the United States to supplement native fish populations as a fast-growing food source. New York Invasive Species (IS) Information, Asian Carp, available at https://nyis.info/invasive_species/asian-carp. However, like other invasive species, the Asian carp has a number of advantages over native fish species that make them so dangerous after establishment in the ecosystems. There are currently four subspecies of Asian carp found in the United States; these include the bighead, black, silver, and grass carp. National Park Service, Asian Carp Overview, available at https://www.nps.gov/miss/learn/nature/ascarpover.htm.
The purpose of the Asian carp was to curtail the growing algal populations throughout the southeastern watersheds. As the primary food consumed in China, it was a logical argument that their success would translate to domestic waters. The Asian carp met its purpose and proceeded to go further. The initial introduction occurred in states like Louisiana and Arkansas. Prairie Rivers Network, Watch Asian Caro Spread Like The Plague, available at https://prairierivers.org/articles/2013/01/watch-asian-carp-spread-like-the-plague/. The Mississippi River is the primary mode of travel through the rest of the country. Asian carp were meant to be contained within the wastewater treatment plants and aquaculture ponds. That was the primary purpose. However, faulty infrastructure and massive floods in the late 1970s and throughout the 1980s broke whatever protections the facilities had in place. The floods created highways for the carps to enter the Mississippi, beginning the vast expansion through the rest of the country.
Like other invasive species, the reason there is rapid population growth is due to a lack of natural predators or any competition with native species for the same food source or space. The four species of carp open the door to different issues in the food chain. The following list briefly outlines what the diets for each type of carp:
- Bighead and silver carp eat plankton, which native mussels and fish depend on.
- Grass carp consume plants and can drastically change river and shoreline vegetation and spawning and cover for native fish.
- Black carp eat snails and mussels, including native species that are already endangered and may endanger reintroduced populations.
National Park Service, Asian Carp Overview, available at https://www.nps.gov/miss/learn/nature/ascarpover.htm. Competition for food like grasses and plankton are naturally balanced between native species. When introducing an invasive species, that balance is in jeopardy. The larger carps, which can reach up to 100 pounds, require massive quantities of food. Id. While those are exceptional situations, the quick reproduction periods allow the carps to rapidly increase populations in a single feeding spot.
The threat to native populations occurs in other ways rather than just competition for food. The grass carp eat vegetation that young offspring of native species need for protection during maturation periods. Not only is there competition among adult native fishes and carp, but there are also significant decreases in population of native species because those species are not able to create viable offspring. Carps are also known to carry disease that can infect fishes around them. Changing the water quality throws the chemical balance in waters into disarray. Adult fishes may be able to adapt to changes in water quality, but once again, the primary threat is to the younglings that are still heavily reliant on certain standards to grow.
Asian carp were designated an invasive species in 1982 when the first population found in Arkansas was considered established. Michigan Watershed Council, Detailed Timeline for Invasive Carp in the United States, available at https://www.watershedcouncil.org/detailed-timeline.html. Since the releases in the 1970s and 80s, it is estimated that there are millions of carp in the wild, yet the actual number is impossible to calculate. The highest concertation remains in southern portions of the Mississippi River, primarily Arkansas, Louisiana, and Missouri. Using the Mississippi as a through-way, northern movement of the carp shows states like Illinois and Iowa having higher concentrations. Established populations of carp also reach as far north as North Dakota. The U.S. Fish and Wildlife Service’s greatest fear is that Asian carp will eventually reach Lake Michigan and overpopulate the rest of the Great Lakes. These bodies of water, if populated by invasive species, would all but eliminate a significant percentage of native species throughout in and adjacent to the Great Lakes.
Since the 1990s, there has not been a successful technique to stop Asian carp moving through the Mississippi. The most effective has been electric fences along the banks of the river. Even with this deterrent, state fisheries are still seeing a significant movement. Other techniques include, like the wild boars in Texas, an open season without any tag limits on catching and killing Asian carp. However, there is no real incentive to do so. The fish was introduced as a food source, but a significant majority of the US population consider these fish as inedible. States and federal agencies are hesitant to use toxins in major river systems for fear of infecting other species of native fish and mollusks.
B. Birds: European starlings
The release of European starlings into the US is noble yet ironic. Where wild boars and Asian carp were introduced to control nuisance species and act as an additional food source, the European starling was merely for show. In the 1890s, 100 European starlings were released into New York city’s Central Park as inspired by William Shakespeare. New York Invasive Species (IS) Information, European Starling, Available at https://nyis.info/invasive_species/european-starling/. The starlings were spoken of numerous times in his novels and plays, and many residents felt it would be artistically important to have those same birds in North America. Id. After numerous attempts, those 100 birds established themselves in the park and began to populate nearby parks and cities. While there are multiple starling species native to the US, including the common starling found in Virginia, European starlings have certain biological differences.
The native and invasive starlings are classified within the same family, yet the European subspecies is unique. Commonly found in Europe, the European starlings have established themselves as a necessary part of the region. Being a ground forager, the starling’s primary diet consists of various insects as well as seeds and fruits. The starlings prefer open grasslands and with low tree or shrub cover for plentiful access to food but have quickly adapted to urban scenes. That adaptation is partly due to the initial introduction in the New York city skyline. The native starlings are not found commonly in urban areas, as they prefer the grasslands with easier access to food. Id.
The biological cycle of a European starling is faster than the native starling, taking only 12 days to incubate eggs, where native species take up to a week longer. Linz, George M.; Homan, H. Jeffrey; Gaulker, Shannon M.; Penry, Linda B.; and Bleier, William J., European Starlings: A Review of an Invasive Species with Far-Reaching Impacts (2007), Managing Vertebrate Invasive Species, 24, available at https://digitalcommons.unl.edu/nwrcinvasive/24. Female birds will reside in the same nesting area during multiple reproductive seasons. Maturing birds will leave the nest and spread well beyond the initial nest to find their own area. This means that the birds will quickly spread over an area and remain in those nesting boxes for their life. Within a year, a single starling will produce an average of 12 offspring in a year. Id.
The issues created by a growing population of starlings range from agricultural to industrial. The ground foraging bird, whose diet is fruit and insects, directly effects product yield from crops like apples, blueberries, cherries, figs, grapes, peaches, and strawberries. Homan, H.J., R.J. Johnson, J.R. Thiele, and G.M. Linz, European Starlings. Wildlife Damage Management Technical Series (2017), USDA, APHIS, WS National Wildlife Research Center, Ft. Collins, Colorado, available at https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/sa_reports/ct_wildlife+damage+management+technical+series. States like Michigan, California, and the northwestern states mass produce many of these fruits. Beyond consuming the seeds and fruits themselves, starlings tend to slash at new crops that have not yet produced fruit to eat, killing a developing plant by exposure to the elements and disease. Id. Massive fruit crop loss can be directly attributed to starlings, where some farms experienced 25% crop loss in a single season. Id. In California, farmers reported a total loss of $70 million in the 2012 harvest season. Over the last 10 years, that number has nearly doubled as starlings continued to expand through the rest of the country. Id.
Where the primary diet comes from wild or agricultural fruits and seeds, starlings also have a direct impact on livestock. Similar to other invasive species, starlings carry with them different diseases not found in native species. The agricultural section of the economy moved towards Concentrated Animal Feeding Operations in the late 20th century. These large farms carry hundreds or sometimes thousands of heads of cattle in one area. The massive operations will usually have open feeding systems, which attract the starlings. This easy access to food is one of the main reasons starlings have moved west into the heartland of the country, where CAFOs are more common. A report from 2012 stated the following:
A flock of 1,000 starlings using a CAFO for 60 days during winter will eat about 1.5 tons of cattle feed, representing a loss of $200 to $400 per 1,000 starlings. About 250,000 starlings that were using a Midwestern feedlot increased the cost of feeding a ration of steam-flaked corn by $43 per heifer over a 47-day period between mid-January and March. Costs in lost production (i.e., livestock weight gained per unit feed consumed) over this period was $1.00 per animal
Homan, H.J., R.J. Johnson, J.R. Thiele, and G.M. Linz, European Starlings. Wildlife Damage Management Technical Series (2017), USDA, APHIS, WS National Wildlife Research Center, Ft. Collins, Colorado, available at https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/sa_reports/ct_wildlife+damage+management+technical+series. Increasing the day-to-day cost of managing a CAFO due to the starlings is one of the major reasons the agricultural sector has petitioned federal agencies to increase controls of the population.
Starlings have a direct impact on the native bird species as well. Where the starlings are hatched and move to a new location to set its own nesting site, the starlings do not always choose to build its own nest. Starlings have been found to attack native species boring in trees to steal the nesting spots. If there are birds present in these nests, starlings can become highly aggressive and kill the current resident. If there are newly hatched birds, starlings will also throw them out of the nest, claiming the current tree as its own. Id.
The other primary danger that starlings come with is that they function as disease vectors. The birds carry with them a variety of different bacterial, fungal, parasitical, and viral pathogens. Not only is this an indirect harm to humans, but the high concentration of starlings near feed lots and crop field easily transmits into the food supply. Amplifying the disease potency without the birds showing many symptoms has caused massive outbreaks of salmonella and gastrointestinal diseases.
In urban areas, the starlings can affect structural elements as well. Where this does not fit the usual understanding of an invasive species harming the native species, it has caused millions of dollars in damages. Maintenance costs in repairing sidewalks, buildings, and cars due to degrading the structural integrity is an expensive feat for cities to overcome. Like the effect on the agricultural sector, unsanitary conditions due to the massive populations endanger public health.
Between the threats to food and water quality, including the harsh economic impacts, the starlings have warranted a number of population controls by local, federal, and state authorities. Like the boars and carp, the starling is not a protected species and very little oversite is present to deal with the growing number of birds throughout the country. Hunting organizations condone lethal measures by farmers to protect agriculture. In cities, lethal traps have been set in order to protect infrastructure and personal property. However, killing a few birds at a time has not yet been an effective mechanism to curtailing the damages the birds cause on a daily basis.
C. Reptiles: the black and white tegu
Invasive reptiles are one of the most recognizable invasive species in the United States. The Burmese python outbreak in southern Florida has been the center of attention whenever the term invasive species is used. As was stated earlier, the massive success of the python in Florida is a prime example of why there must be some control mechanisms in place. Another species that has recently been added to the invasive species list in the black and white tegu.
Tegu is the common name for lizards from the family Teiidae and Gymnophthalmidae. Native to Argentina, the black and white tegu (Salvator merianae) has established itself in Florida and has been found well beyond the Everglades where most invasive reptiles are found. These animals can grow nearly five feet in length and have an omnivorous diet that includes fruits, eggs, insects, and small animals including reptiles and rodents. Not only does the black and white tegu pose a competition and direct threat to native wildlife, but adults have few predators and give birth to large numbers of offspring. Florida Fish and Wildlife Conservation Commission, Argentine Black and White Tegu, Salvator merianae (last visited July 26, 2022), available at https://myfwc.com/wildlifehabitats/profiles/reptiles/argentine-black-and-white-tegu/.
It is unclear how the tegu has established itself, but the general consensus is that it was an exotic pet that was released. Like other invasive species, the rapid reproductive rate and lack of any consistent predator has been the catalyst to the growing population.
The tegu’s greatest threat is that it consumes native species of birds, other reptiles, and fish. It has a very similar growth pattern in population as the Burmese python, as both use the warm and brackish waters of southern Florida to hunt its prey. Where the boars, starlings, and carp directly affect humans and infrastructure, the only real threat is how the tegu is eliminating native species. as with the python, the endangered species found in the everglades are at the highest risk by the reptile.
The tegu is not on any form of protected species list, allowing for individuals on private land to hunt as deemed necessary. Using toxins and traps are dangerous to native species, so the chosen method has been shooting on sight. Beyond the impact on local species like turtles, fish, and other reptiles and amphibians, this new invasive species has not been fully established as a universal threat. Only in the last decade has Fish and Wildlife Services recognized this introduced species as an invasive species, and the dangers an invasive species brings with it.
D. Mammals: feral pigs
Nonnative mammalian species can be found throughout the world, a significant number of which currently reside in the United States. Some of the more surprising names on the list of nonnative mammalian species include feral cats, domestic cattle, a variety of goats, six species of deer, and a dozen species of rats. The source of these animals can be the intentional movement from places like Europe for the purpose of food or protection in the States. A significant number of these mammals were also brought over from Europe and Asia through shipment channels that brought more than just cargo. One of the most prevalent and dangerous nonnative mammals in the United States is the feral pig, also known as the wild boar.
Like most invasive mammal species, the wild boar was introduced in the 1500s by early settlers as a source of food. Mississippi State Extension, History of Wild Pigs (last visited July 26, 2022), available at https://www.wildpiginfo.msstate.edu/about/history.php. Over the course of the next four centuries, the population boom in western states and resulted in a need for more food. Cattle were the primary source of food for those western states. However, wild boar was not far back on the list. Free range boars and escapees from rearing pens provided an opportunity for these boars to grow well beyond their initial population.
As a result, feral pigs are currently found in at least 35 states, the highest concentration coming in the southwest portion of the country. USDA-APHIS, History of feral swine in the Americas (February 24, 2022), available at https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/operational-activities/feral-swine/sa-fs-history. A rough estimate of their population reaches 6 million as of 2022. The primary food of the feral pig consists of grasses, shrubs, and important food for native species, like the hickory nuts. Seward, Nathan W.; VerCauteren, Kurt C.; Witmer, Gary W.; and Engeman, Richard M., Feral Swine Impacts on Agriculture and the Environment (2004), Sheep & Goat Research Journal 12, available at https://digitalcommons.unl.edu/icwdmsheepgoat/12. The omnivorous animal also eats insects like worms, beetles, and other arthropods. The hogs also eat economically favorable food like chicken, chicken eggs, white-tail deer fawns, and livestock. Agriculture and native systems are threatened by the growing population and the massive amount of food a hog must consume in a short-period as it migrates through the southwestern region. The range of the hogs reach to the southeastern beaches, where animals like sea turtle eggs are susceptible to their burrowing techniques, as well as endangering local human beach goers. Hogs are also one of the most dangerous animals due to their high infection rate, carrying dangerous diseases that are transferrable to both animals and humans. The aggressive animal significantly threatens the health and economic side of both native animals and humans living in the hog’s territory. Id
In line with the Burmese python and its effect in the Everglades, the wild boar population rapidly increased without many checks and balances. Where the pythons are restricted to an environment that is specific to reptiles, the expanses of the American south and southwest provided ample space for the population to grow. The ample space coupled with the wild boar’s natural ability to reproduce quickly and have a healthy yield during breeding seasons outpaced many of the other native species for access to food.
Animal activists and the academic community has acknowledged the inherent value of mammals over other subspecies due to the discovered intelligence. Richard Cupp, Cognitively Impaired Human, Intelligent Animals, and Legal Personhood, 69 Fla. L. Rev. 465 (2017), available at https://scholarship.law.ufl.edu/flr/vol69/iss2/3. Research into the awareness of dogs and cats, those being companion animals, has reflected that other mammal species share many of the same physiological and mental features. Intelligence was one of the limiting factors as to why animals did not receive any rights prior to laws like the Animal Welfare Act and state anti-cruelty acts. Fish, reptiles, and birds have yet to receive the same respect as mammals as the general public sees them as lesser species. That is a reflection as to why boars have additional protections in some states, like Texas, whereas a state like Florida has yet to create provisions over the ethical treatment of reptiles.
In the 1990s, the hogs were classified as agricultural pests, meaning there were very little control mechanisms were in place. It was left to the farmers or other communities to control the growing populations. Since the 1990s, there have not been many changes in how hog populations are controlled. Simple shooting, trapping, or adding toxins to some food sources select to the hogs were the only techniques. Strong animals would break through any level of fencing, and with free-range livestock populating the southwest, the hogs have had a “buffet” on every level of food sources, native wild species, and domestic livestock.
Today, states like Texas and Georgia classify hogs as “unprotected, exotic, and non-game animals.” Rick Taylor, Texas Parks and Wildlife, The Feral Hog in Texas, available at https://tpwd.texas.gov/publications/pwdpubs/media/pwd_bk_w7000_0195.pdf. This classification means there is no hog season and without any bag-limits on how many hogs a person can kill in a specified time period. All someone needs to hunt hogs is a valid hunting license and landowner permission. Where there are some welfare-based techniques, they are not nearly as effective, as will be seen in Section IV.
IV. Animal Welfare Considerations and Invasive Species
Reviewing state law shows how welfare considerations for invasive species is lackluster. Companion animals and native species have numerous anti-cruelty statutes regarding the day-to-day treatment of animals as well as control mechanisms. Originally, feral cats were classified as an invasive species. The treatment of feral cats reflects how views change depending on the species' relationship with humans; eradication was once of utmost importance as feral cats threatened public and private property, including detrimental effects to agriculture. Domestication changed the public perspective of how feral cats are treated, with state and federal laws giving the greatest controls for what a person may do to control the population.
The successful integration of the feral cat in modern life is likely not going to be the same for the invasive species listed here. There is nothing explicitly stated in federal or state law that would include invasive species in the anti-cruelty legislation. Certain laws include invasive species in its bylaws, but not for protecting the invasive species itself. For example, the Lacey Act focuses on controlling invasive species for better protecting domestic and native species. Forest Legality Initiative, The Lacey Act, available at https://forestlegality.org/policy-law/us-lacey-act. The Lacey Act does not include any information about how the domestic animals are protected from invasive species, just that it is an important action.
The most concrete example of recognizing an invasive species of deserving some rights and some ethical treatment is the boas in Florida. Where the reptile does not share the same general sentiment as a dog or cat, there are thousands of boas that are held as exotic pets. In fact, the invasive population is thought to originate from released pet snakes. Because animal rights has yet to reach reptiles, birds, and fish, these pets do not hold the same rights that dogs or cats have. However, state anti-cruelty acts still maintain that animals should not be treated in a cruel and unethical way. Florida Fish and Wildlife Conservation Commission, Removing Pythons in Florida, Available at https://myfwc.com/wildlifehabitats/nonnatives/python/removing/. The boas do not have any explicit laws about how they should be treated but are protected by the state’s anti-cruelty laws. Within those provisions, hunters and trappers must still honor rules about limiting any pain or suffering to which an animal may be exposed.
The role that invasive species play in economic hardship and loss of biodiversity has led most members of the general public to understand eradication is the only option. Damage done to crops and livestock by boars, the spread of disease from European starlings in rural and urban area, threats of extinction to significant endangered populations of native species in the Everglades by boas and the black and white tegu, and the total overpopulation of dangerous species like the Asian carp are few of the examples of why the public believes any animal welfare value for these animals is outmatched by the damage they do onto native areas.
Courts and states have agreed that the impact of invasive species will outweigh many of associated economic burdens placed on companies such as those shipping through the Great Lakes. The Michigan Supreme Court upheld a decision in 2009 that affirmed the legality of a law that would force shipping groups moving from the Atlantic and into the Great Lakes to dump the ballast water and wait a defined period for any invasive species, like zebra mussels, to die in the salt water east of the lakes. Noah D. Hall, Michigan's Ballast Water Law Upheld, Allows States to Take Action to Stop the Spread of Invasive Species, ABA Water Quality & Wetlands Committee News, January 2009 at page 10. Where the federal government had holes in the ballast water regulations, states like Michigan saw it necessary to create additional safety measures to ensure the movement of dangerous invasive species does not further progress. Fednav v. Chester, -- F.3d -- (Case No. 07-2083, 6 th Cir. Nov. 21, 2008).
Where animal advocates and those against invasive species and are willing to take opposing drastic measures, there are some middle ground options. The most prominent movement to control invasive species, while still maintaining animal welfare, is containment. Under this theory, rather than building fences to protect property or building other exclusion infrastructure, structures will be erected to contain the animals to a specific space. This acknowledges the need to mitigate and moderate the movement and effect invasive species may have in an area but also focuses on the welfare of animals. Hutchins, M., Stevens, S., & Atkins, N. (1982), Introduced species and the issue of animal welfare, International Journal for the Study of Animal Problems, 3(4), 318-336, available at https://www.wellbeingintlstudiesrepository.org/acwp_ehlm/5/. Despite this movement that has welfare of the animals as a primary motivator, critics cite the following as to why lethal measures are more effective than containment:
First, fences meant to contain exotic animals can also prevent the natural movements of native species (Carothers eta/., 1976).
Second, by restricting the animals to a particular area, the degree of environmental modification is often intensified locally.
Third, containment may not be possible because of the difficulty associated with keeping certain animals in the desired area; for species that can climb, jump or burrow, effective containment would be difficult and expensive.
Id. Conflicting views about which species are more worthy of protection are reasons why the general public grapples with the idea of whether or not certain animals, especially those invasive species, deserve increased rights under the lens of welfare.
The arguments about invasive species and how to deal with the ever-growing influence is dichotomous: does the preservation of a native species outweigh the rights of an invasive species? With animal welfare being a newer concept, issues like invasive species welcome division in those pro and against welfare of animals. Animal welfare for companion animals has grown significantly over the course of the last two decades. The public recognizing the importance of protecting the environment has been developed over the last five decades. Recognizing the value of the environment links to the welfare for the animals living within the environment as well. With that in mind, as animals and the environment growing more inherent value, the issues arise when considering when the two are at controversy. The role invasive species play on the environment is drastic, as can be seen in the case studies above. However, animal welfare is constantly being expanded to more and more mammalian species, with avian species and fish not far behind.
It is relative to the person over whether or not invasive species warrant any animal welfare. The public’s general consensus is that invasive species should be eliminated as soon as possible as the amount of damage done mounts every day. One question to consider is under what circumstances is elimination of exotic animals justifiable? As can be seen through the case studies, invasive species cause difference levels of damage depending on species, location, and the species' ability to expand its geographic location. There are two simple options in relation to invasive species: eradication and containment/exclusion. Park services and state wildlife groups have a variety of different tests and observations that lead to conclusions of how much harm a specific invasive species will cause to an area and over some arbitrary period of time. With those results, elimination or containment are the viable options to slow the damage. Activists for animal welfare strongly believe that even though substantial damage is done at the hands, claws, beak, or fangs of invasive species, the moral value means extermination should not be utilized. A significant number of wildlife control services believe that the welfare of native species and the environment far exceeds any value that an invasive species may carry, leading to eradication as the favored method.
It is unlikely invasive species will receive the same rights an many native species hold today. Public sentiment and environmental ethics will be the main limiting factors as to why control mechanisms for invasive species will sit on a middle ground from cruel to necessary. It is difficult to calculate, but a type of legal and ethical equation may hold some answer to this question. Environmental and animal ethics traditionally align with one another, yet the differences begin to materialize when factoring in invasive species:
If we consider the ecosystem first,  the course of action might seem obvious: remove the invaders. But individualist animal ethics put significant weight on traits which the invasive animals in question, depending on their species membership, [and examining features like] sentience or the capacity to experience pain. It is not always clear how to take commitment to ecosystems . . . into account alongside commitment to individual animals, beyond simply agreeing to let one trump the other.
Emily C Parke, James C Russell, The Ecological Citizen Vol 2 No 1 2018: 17–19 [epub-013], Ethical responsibilities in invasion biology, https://www.ecologicalcitizen.net/article.php?t=ethical-responsibilities-invasion-biology. The balancing test between the two belief systems is why it will be unlikely any changes to the current polices will include protections for invasive species. Significant changes in public understanding of invasive species and the animal’s inherent value will be the main avenue that will allow documented rights for the invasive species. Until then, agency and public control mechanisms will be free from most laws based around ethical treatment of animals, focusing on mitigating pain and suffering.
V. Control Methods for Exotic Animals and Animal Welfare
The need for steadfast and effective control mechanisms for invasive species can be categorized by either direct controls or indirect. Each method will bear pros and cons, including success rate for limiting the impact of invasive species versus the difficulty in administering effective means.
A. Direct control
Upon initial review of the species discussed thus far in the paper, certain actions are intuitive; if there is a problem species, the only course of action is killing it. Along those lines, the basic idea of ridding a species is far more complex than just putting the broad label "invasive" on it.
For mammals, the larger species are easy to spot. A wild boar running through a wide-open field can be seen by the naked eye. A tracker will be able to see certain features in a field that show wild boars were in the area. As of right now, the primary choice to control wild boar populations is the open-season hunting. Native species are heavily regulated by state and local natural resource departments to ensure the health of the animals and their role in the ecosystem. When there are no limits on how many invasive animals a hunter may kill, a regulating body acknowledges that either there is not a threat to the ecosystem by removing a significant member of the food chain or the animal is a greater threat to the fragile system. In the case of boars, the damage that can be done to farmers fields and property can be extreme. Having an open season allows farmers and property owners control the population as they see fit. Another technique that is used for capturing a nuisance mammal is trapping. The boars will work through an area quickly, without much regard for what is around them. With that, hunters will lay a variety of traps, like the snare trap, to capture and kill the boars without having to actively seek them out.
The open season hunting, and no bag limits are also available to the other families of species listed above. The state of Florida holds events for the number of Burmese pythons can be caught in a specified period of time. See, for example, Florida Python Challenge, available at https://flpythonchallenge.org/. Similarly, though not to the level of the Florida Python Challenge, a number of hunting groups organize massive hunts for European starlings in rural areas. Asian carp, famous for jumping out of the water up to 10 feet in the air, are a sight to see in places like Kentucky where they hold bowfishing challenges. Competitors also adorn helmets and mouthguards and proceed to water ski through open water with fish jumping around them. In many ways, this puts a jovial sense on the dangers of an invasive species. On the other side, competitions like these estrange the animals from people recognizing the welfare value these animals have.
The welfare concern when it comes to an open hunting season and trapping animals is one not traditionally discussed in terms of invasive species. Many state anti-cruelty laws have exceptions for hunting and wildlife management by the state and others have declined to put specific language regarding hunting. As a major industry, the laws protecting animals usually apply to companion animals, not necessarily those that can be hunted recreationally or on private property. Animal Legal Defense Fund, Laws that Protect Animals, available at https://aldf.org/article/laws-that-protect-animals/. It is not a legal question, but rather a moral one on whether hunting serves a purpose in the world or not. In light of law, as long as the acts are done within what is required by the hunter, the state and federal laws will not apply. Where hunting with a firearm allows for an individual to be more selective when killing an animal, traps do not have the same filter. Boars live amongst other foraging animals and if a trap is placed to attract and snare a boar, it is likely other native species are at risk. Trapping is a heavily contested mode of hunting as the animal experiences immense pain and suffering from when it is first snared to when it eventually dies at the hands of the person who laid the trap, another animal, or physical or mental stressors.
B. Indirect control
Beyond direct hunting, other population control mechanisms for invasive species consist of poisoning and deterrence by containment (discussed infra at Section IV). Whether it is infecting the water supply or creative bait traps for a specific species, the plan for poisoning is the same as trapping. On its face, placing toxic foods or water in an area will attract the animal and kill it effectively. There are also numerous issues when it comes to placing toxic substances in the wild: it can affect other species and its moral value is in question. The primary way to kill invasive species via poison is placing it in an area with easy access, hidden in area like a bush or shrub near where the animals would find their food. For starlings, poison is placed in trees or on ledges where they nest. For fish and reptiles, it is much more difficult as diffusing poison in water or in the everglades makes it impossible to target the specific species in question.
Where removing invasive species is of utmost importance, the removal methods raise a number of ethical concerns. In line with anti-cruelty laws, multiple states have exempted invasive species from the protections that are applied to all animals. By limiting what rights the invasive species have, the door to unethical methods that result in pain and suffering is more than open. Where a great majority of invasive species eradication approaches border on immoral, there are a number of other options wildlife services may pursue.
VI. Conclusion and Policy Application for Management
The impact invasive species have on local ecosystems and national economy warrant intense public and governmental focus. Eradication is one of the only options to returning a local biome to original health. With invasive species growing and further establishing themselves across the country, it is paramount to curtail the growth sooner rather than later. Where that eradication is typically associated with killing the animal, there may be more humane choices to control invasive species without sacrificing the value that animals have.
Species specific controls is not a new phenomenon. Even with native species, certain actions are pointed directly at ensuring populations of a species do not overgrow others. In line with the ideas discussed above, the purpose of hunting season for many species is population control. For protecting property, landowners have used fences throughout agricultural history to manage where species can move. Infrastructure has been built to manage where species may be and how many there can be in an area. Each of these direct controls are condoned by wildlife professionals across the country because of the ecological and economic issues that invasive species present.
The Asian carp controls mechanisms is the most well-known of the invasive species listed thus far. As the fish migrated north through the 1990s, electric fencing and dams were built to slow the growth. These barriers were made to deter the fish from continuing north along the Mississippi and stop the movement into tributaries as well. However, the choice to deter the Asian carp also came with deterring native species, like trout and river catfish. The success of the barriers was also not what the state DNR’s expected. The thick scaled carp were able to withstand much of the electric signals the fences gave off. The swimming patterns also allowed the fish to circumvent most of the barriers. The famous jumping carp was first seen whenever the barriers turned on, simulating a motor.
Avian species like the European starling have easier control mechanisms compared to boars. Repelling birds from infrastructure is not a foreign concept. Across cities, to prevent birds from nesting on buildings or other structures have led engineers to add spikes or fishing line to repel birds. Acting as both direct and indirect controls, limiting the population is done by both private landowners and wildlife agencies. Parallel to the boar, the current control that is most effective is trapping or netting. Large nets over buildings and housings capture the birds and allow for relocation or lethal control measures. These nets are like the snare traps for boars and welcome the same ethical concerns. The pain and suffering in nets is not a well-known or acknowledged issue, as the prevalence continues to expand.
Reptiles, like boas, do not have any concrete plans in place to deal with the growing populations, outside of the hunting opportunities. The primary plan of attack to deal with the growing populations is to start at the source: prevent the introduction entirely. Most of the animals found in southern Florida and throughout California established themselves from exotic pet owners that no longer wanted them. Controlling that source is the best way to stop a population that grows with every introduction of another fertile male or female reptile. Toxins may be used but are not the optimal way to control populations as most reptiles found in the same ecosystem consume and same food and would be exposed to the same dangers. The number of endangered species found in tropical areas of the continental United States are controlled by the EPA and Endangered Species Act, meaning any control mechanism looking to be used must be critically vetted.
In the case of the wild hogs, most of the damage done to the wild fauna is hard to mitigate. There is no concrete way to prevent the hogs from eating shrubs and bushes the native species also consume. For those hogs, the only actions that have great success is hunting, trapping, and building larger, sturdier fences. The cost to the landowner and those actors looking to control wild boar populations is hard to quantify. Where hunting and trapping due not bear a great cost, this long-term solution allows the damages caused by boars on a day-to-day basis to grow. Short-term solutions like fencing is the more expensive route, as it is essentially overhauling hundreds of thousands of miles of fences to protect properties across the country.
The impact an invasive species will have on a native ecosystem is difficult to quantify but is clear to the naked eye. Scientific studies and ecological reports have concretely showed that the introduction of an invasive species will have significant long-term and short-term effects on a single area. Recovery from the damage an invasive species does to an area is the goal, but this is hard to imagine for some areas of the country including the Everglades. Those direct and indirect controls hold their fair share of successes, but some of the more effective means also carries with it ethical concerns. State and federal laws do not explicitly mention invasive species in provisions protecting animals from pain and suffering. An altruistic goal in the mind of an animal activist is that all animals should be protected by the same laws. However, public outrage at the effects an invasive species have will limit any law along those lines from being recorded and implemented.
A difficult solution to the environmental and animal ethics can be setting baseline laws that go beyond merely including rules from state anti-cruelty acts. Where the federal government has been hesitant to create laws that outright protect all animals from pain and suffering, it is necessary to acknowledge the treatment of invasive species certainly border cruel. It is not feasible to create a new policy that would include protections for invasive species but amending laws like the Lacey Act to include language about avoiding pain and suffering would be a step in the right direction. The public perception of what an animal is ethically worth is another barrier as some see mammals of more worthy of rules requiring the limitation of pain and suffering. More and more research is finding that fish, birds, and reptiles have some of the same neurological features found in mammals, including humans. It would be a difficult path to change both public and the legislature’s mind about how invasive species should be treated, but it is the duty of both to ensure proper treatment of all animals is universalized.