Michael P. Glow 

Wildlife Biologist

USDA-APHIS-Wildlife Services

National Wildlife Research Center 

Fort Collins, Colorado 

 

Nathan P. Snow 

Research Biologist

USDA-APHIS-Wildlife Services

National Wildlife Research Center

Fort Collins, Colorado

Kurt C. VerCauteren 

Supervisory Research Wildlife Biologist

USDA-APHIS-Wildlife Services

National Wildlife Research Center

Fort Collins, Colorado

 

Human-Wildlife Conflicts

Feral swine (Sus scrofa; Figure 1), also 

known as feral hogs, feral pigs, wild pigs, 

wild boar, or other similar derivations, are 

a non-native species considered to be one 

of the most destructive invasive terrestrial 

vertebrates in North America. While feral 

swine populations remained relatively 

small and confined in the continental 

United States following initial introductions 

by European explorers during the 15th

century, substantial range expansion has 

occurred across every geographical region 

of the United States (Figure 2). This 

expansion has primarily been attributed to 

human-mediated movements, 

predominately for the purpose of 

establishing populations for recreational 

hunting, and facilitated by feral swine’s 

highly adaptable biological and behavioral 

traits (e.g., habitat generalist, opportunistic 

omnivore, extremely high reproductive 

rate). Consequently, ecological, 

agricultural, and urban/suburban 

damages and human health and safety

Wildlife Damage Management 

Technical Series

U.S. Department of Agriculture

Animal & Plant Health Inspection Service

Wildlife Services

August 2020 Feral Swine

Figure 1. Feral swine (Sus scrofa).

Quick Links

Human-Wildlife Conflicts 1

Damage Identification 4

Management Methods 5

Economics 12

Species Overview 13

Legal Status 18

Glossary & Key Words 19

Resources 20

Appendix 21
risks have increased substantially across the United 

States, requiring extensive management efforts to mitigate 

their destructive impacts. 

Agriculture and Livestock

Feral swine cause substantial damage to agricultural 

resources, primarily through the consumption and 

trampling of crops (Figure 3). Corn, peanuts, grapes, 

wheat, soybeans, rice, sorghum, and a considerable list of 

additional crops are all damaged by feral swine. Type of 

crop, proximity of crop fields to forest edges, and crop 

growth stage all influence the severity of feral swine 

damage. Substantial economic losses occur each year, 

sometimes forcing agricultural producers to plant lessprofitable crops that are less desirable to feral swine in 

order to avoid additional losses due to damage.

Pastures and hay fields are damaged due to rooting by 

feral swine. This not only results in the loss of forage and 

costs to repair fields, but also may degrade the nutritional 

quality of pastures over time as less nutritious invasive 

plant species colonize disturbed pastures and replace 

native grass species. 

Feral swine also damage fences, irrigation ditches, 

livestock feeders, and irrigation lines. Additionally, rubbing, 

tusking, and depredation of tree seedlings by feral swine 

negatively impacts the timber industry. 

Disease transmission is the primary threat feral swine pose 

to livestock. Historically, the domestic livestock industry 

has implemented extensive efforts to eradicate many 

diseases that threaten livestock. However, feral swine are 

reservoirs for these diseases, including pseudorabies, 

swine brucellosis, and at least 30 other diseases that may 

be transmitted to livestock indirectly (e.g., feral swine 

accessing stored feed that is then fed to livestock) or 

through direct contact (Figure 4). Disease outbreaks 

spread by feral swine can be difficult and costly to manage 

and constitutes a significant economic risk. While foreign 

animal diseases, such as foot-and-mouth disease and 

African swine fever, are currently absent in the United 

States, there is a growing concern that feral swine could 

spread these diseases, resulting in potentially devastating 

impacts to the livestock industry. 

Archaeological and Historical Sites

Damage occurs to archaeological, cultural, and historical 

sites due to feral swine rooting. Rooting can disturb, 

expose, and degrade the presence of artifacts and reduces 

the aesthetic value of these sites. 

Figure 2. Feral swine populations by county in the United States, 2019.

Page 2 WDM Technical Series─Feral Swine

Figure 3. Feral swine damage to corn.
Ecological

The magnitude of ecological damage attributed to feral 

swine is extensive. One of the most pervasive forms of 

ecological damage occurs as a result of feral swine rooting 

and wallowing (Figure 5). Although rooting and wallowing 

damage may vary annually and spatially, these behaviors 

affect a wide range of plant and animal species, including 

numerous threatened and endangered species (e.g., lesser 

prairie chicken (Tympanuchus pallidicinctus), Houston toad 

(Bufo houstonensis), Hawaiian moorhen (Gallinula 

chloropus sanvicensis)), by negatively altering the 

composition of ecosystems. For example, after rooting, 

habitats once composed of a diversity of beneficial native 

plant species are often colonized by invasive plant species 

that out-compete native species and provide little to no 

benefit to wildlife. Seed dispersal of invasive plants by feral 

swine further facilitates the spread of invasive species. 

Natural regeneration of coniferous and deciduous tree 

species in woodland ecosystems is often inhibited as well 

due to feral swine rooting and consumption of hard mast 

(e.g., acorns). Negative soil impacts, such as soil 

compaction and disruptions in nutrient cycling and soil 

chemistry may also occur. 

Rooting and wallowing near watersheds and sensitive 

aquatic systems can negatively impact water quality due to 

erosion and sedimentation, algal blooms, oxygen 

depletion, and pathogen dispersal. Additionally, damage to 

marsh and wetland habitat negatively alters flood control, 

water filtration, and surge protection.

Feral swine compete for a variety of food resources with 

native wildlife species (e.g., wild turkey (Melagris spp.), 

raccoons (Procyon lotor), black bear (Ursus americanus)). 

In particular, hard mast is an important food source for 

feral swine, but numerous wildlife species, including whitetailed deer (Odocoileus virginianus) and squirrels (Sciurus 

spp.), depend on this resource as well. 

Although feral swine primarily consume plant matter, they 

also present a risk to numerous wildlife species through 

direct or opportunistic predation. Wildlife at risk includes 

ground-nesting birds and their eggs, invertebrate species, 

small ground-dwelling mammals, reptiles, and amphibians. 

Threatened and endangered species are also at risk to 

feral swine predation, including green sea turtle (Chelonia 

mydas) eggs. 

Human Health and Safety

Feral swine carry many diseases and parasites that can be 

spread to people. Hunters or anyone who may come in 

contact with carcasses or eat feral swine meat are 

particularly susceptible. In several states, hunters have 

contracted brucellosis or trichinosis after butchering feral 

swine without gloves or eating undercooked meat, 

respectively. Therefore, it is highly advised that anyone 

butchering or handling feral swine meat use appropriate 

personal protective equipment (e.g., latex gloves) and cook 

meat to a safe internal temperature of 170° Fahrenheit. 

Trichinosis symptoms include abdominal pain, diarrhea, 

muscle pain, fever, and fluid accumulation and the severity 

will depend on the number of larvae ingested. Flu-like 

symptoms, headaches, fever, weakness, and muscle 

soreness are commonly associated with brucellosis and 

may be chronic.

Human food and water contamination is also a risk and 

concern. Feral swine were a potential cause to a 

nationwide E. coli outbreak in 2006 due to contaminated 

spinach from California that resulted in 205 illnesses and 

3 deaths. Positive samples for E. coli were obtained 

U.S. Department of Agriculture Page 3

Figure 4. Feral swine are reservoirs for disease that may be transmitted to livestock.
from feral swine in the immediate area surrounding the 

contaminated spinach fields. 

Feral swine-vehicle collisions are becoming an issue, 

especially in highly populated areas, resulting in physical 

injuries, potential fatalities, and significant damage to 

vehicles (Figure 6). 

Increasing populations of feral swine in developed areas 

also increases the risk of attacks on people and domestic 

pets. Although rare, attacks do occur and can cause 

serious puncture wounds and lacerations. Most attacks 

occur when feral swine are threatened or cornered, but 

may also occur when unprovoked. In some cases, feral 

swine attacks have killed people.

Urban/Suburban

Damage to urban and suburban areas has been increasing 

as feral swine continue to expand their range and are 

attracted to anthropogenic resources available in these 

areas. Rooting damage in residential yards, cemeteries, 

golf courses, parks, sports fields, and levees is common 

(Figure 7). Destruction of ornamental landscaping, fences, 

and irrigation systems also occurs. Feral swine can 

compromise the integrity of power poles through extensive 

rubbing.

Damage Identification

Feral swine are often nocturnal, especially in areas where 

they are heavily pressured, so relying on direct 

observations may not be a good indicator of their 

presence. However, the appearance of feral swine tracks 

and sign (e.g., wallows, tree rubs, beds, scat; see Tracks 

and Sign section) will indicate they are in the area, 

translating to probable damage.

Page 4 WDM Technical Series─Feral Swine

Figure 5. Feral swine cause ecological damage from their rooting (left) and wallowing (right).

Figure 6. Feral swine-vehicle collisions are increasing.
Rooting is one of the most common and easily 

distinguishable signs of feral swine damage and is 

characterized by excavated or upturned soil. Depth and 

extent of rooting varies from shallow to extensive 

disturbances up to 3 feet (ft) (0.9 meter (m)) in depth. 

Rooting occurs in a variety of habitats, including 

grasslands, forests, marshes, wetlands, pastures, and 

agricultural fields. However, intensity varies seasonally and 

among different habitat types, often based on food 

availability.

The timing of crop damage varies based on individual 

crops and different growth stages, reflective of varying 

nutritional values during different stages. Recently planted 

crop fields are commonly damaged as feral swine will root 

straight lines and consume seeds along each crop row 

(Figure 8). Rooting, trampling, and direct consumption are 

all indicators of feral swine damage during the vegetative 

and fruiting stages, but sometimes may be confused with 

deer damage. Damage is typically concentrated along field 

edges, but may be more widespread in smaller fields 

where the proximity of escape cover is closer. Feral swine 

may use crop fields for cover, which can also cause 

extensive damage. Damage to tree seedlings in forest 

plantations is indicated by masticated root clumps that 

feral swine have chewed on, consumed sap and starches, 

and then spit out. 

Although feral swine depredation on livestock may be 

confused with other types of predator depredation, signs 

include consumption of the rumen or stomach contents, a 

skinned carcass, and crushed skull or neck. 

Management Methods

Management of feral swine is often confounded by 

numerous ecological, social, and economic factors which 

must be taken into consideration when determining 

optimal management plans. Further, given the adaptability 

of feral swine and the ability to reproduce rapidly, the use 

of a single control method is rarely advised. Multiple 

control techniques used in an adaptive, integrative 

management framework that incorporates region specific 

biological and ecological factors (e.g., seasonal availability 

of food resources, predominant habitat types, timing of 

feral swine birth pulses) and various stakeholder 

perspectives is highly recommended. Management 

objectives should also be considered before determining 

specific management actions and if those objectives are 

feasible. For example, eradication may be the goal, but is 

often very difficult and cost-prohibitive in areas where feral 

swine populations are high. Thus, population reduction to 

mitigate damage to a tolerable level may be more 

achievable. 

U.S. Department of Agriculture Page 5

Figure 7. Rooting damage to lawns, golf courses, and cemeteries is common.

Figure 8. Recently planted crop fields are commonly damaged as feral swine will root 

straight lines and consume seeds along each crop row. 
Page 6 WDM Technical Series─Feral Swine

Numerous lethal and nonlethal control techniques are 

utilized to control feral swine and mitigate their damage. 

While lethal control techniques are often most effective, 

nonlethal control may also be used effectively, especially 

when used in conjunction with lethal techniques. The use 

of lethal techniques may also be restricted in certain areas, 

such as urban and suburban environments, requiring 

nonlethal techniques to reduce damage. 

Repeated and intensive removals of feral swine may be 

needed to keep populations low because populations 

rebound quickly following drastic declines. Therefore, 

annual removal of a substantial percentage of feral swine 

may be required to keep a population from increasing, 

especially in highly productive areas. 

The following feral swine management methods are listed 

in alphabetical order.

Education

Ensuring landowners and other stakeholders responsible 

for feral swine management on private lands are aware of 

the most current and effective control options and how to 

properly implement those techniques is very important to 

maximize management efforts. Numerous informational 

outlets from state and federal agencies, university 

extension cooperatives, and other organizations are 

available in the form of workshops, outreach events, 

educational materials, websites, YouTube channels, and 

field events. 

Public education is vital for future management efforts 

(Figure 9). All too often, false or inaccurate information is 

obtained from non-scientific sources including the internet 

and word of mouth. Informing the public and policy makers 

with science-based information regarding the destructive 

impacts of feral swine is crucial to gaining public and 

political support for management efforts. Raising public 

awareness of the risks associated with human-mediated 

movements of feral swine is also extremely important. 

Management efforts are largely ineffective and wasted in 

areas where control is negated by continued humanmediated movement of feral swine into the area. 

Additionally, agencies tasked with controlling feral swine 

must stretch their resources to control new populations of 

feral swine established by people, in addition to already 

established populations.

Fencing

Temporary fencing can provide a short-term solution to 

mitigate feral swine damage to resources, including 

agricultural crops and sensitive ecological areas. For 

example, a 2-strand, polywire electric fence at 8 and 18 

inches (in) (20 and 46 centimeters (cm)) from the ground 

has been shown to temporarily protect agricultural 

resources and provide a relatively inexpensive fencing 

option. Hog panel fencing 5 ft x 16 ft (1.5 m x 4.8 m) may 

also be used to protect specific areas from damage (Figure 

10). Permanent fencing options may provide long-term 

solutions for keeping feral swine out of high-value crops, 

airports, or other areas where the expense is warranted. 

Cost, effort to install, and longevity of fencing varies by 

fence type, and its effectiveness often depends on the 

motivational level of feral swine to access the resources 

being protected. 

Fertility Control

Although interest in the use of contraceptives as a 

humane, nonlethal control technique for feral swine has 

increased, none have been registered for use in the United 

Figure 9. The National Feral Swine Damage Management Program and its 

local, state, and federal partners provide a variety of information on feral 

swine ecology and damage management to the public.
States. Ideally, contraceptives need to render a 

considerable proportion of a feral swine population 

permanently infertile following a single dose. Research has 

shown that gonadotropin-releasing hormone (GnRH) 

injections could provide an effective fertility control agent, 

but alternative forms of administration (e.g., orally) need to 

be developed for applicability in large-scale operations. 

Additional forms of contraceptives are also being 

developed, but additional research is required. Similar to 

toxicants, feral swine-specific delivery methods also need 

to be developed for contraceptives in order to reduce the 

risk of exposure to non-target species. 

Frightening Devices

Frightening devices may provide short-term relief from feral 

swine damage, however, limited efficacy and applicability 

have been reported. Variations of blinking or bright lights 

and loud, piercing noises have been tested with limited 

success. Similar to repellents, feral swine eventually 

become habituated to these devices, rendering them an 

ineffective long-term solution. 

“Judas Pigs”

The “Judas pig” strategy helps to inform feral swine 

removal efforts by identifying areas where pigs may be 

present. It involves equipping individual feral swine with a 

global positioning system (GPS) or very high frequency 

(VHF) device (Figure 11). Their locations are then 

monitored to determine where additional feral swine may 

be present based on the assumption that the Judas pigs 

will seek out and gather with other groups of pigs. 

Research is needed to determine the best sex or age class 

for Judas pig candidates. 

Monitoring

Monitoring is an essential part of evaluating the efficacy 

and success of any management program. Metrics that 

demonstrate the success of a program, such as the 

proportion of a population removed or the amount of 

damage prevented, are more informative than solely 

reporting the total number of feral swine removed. If 

eradication or significant population reduction is the goal, 

management efforts will ultimately be ineffective if, for 

instance, 100 feral swine are removed, but those 100 feral 

swine only represented 25% of the total population. Trail 

cameras are commonly used to monitor feral swine 

populations and damage assessments are conducted 

before and after removal efforts. Researchers are working 

to develop quick and easy methods to quantify these 

metrics.

Once established, feral swine populations can be 

extremely difficult to control. Therefore, monitoring and 

early detection are often the focus in areas where feral 

swine are currently absent or have recently been 

U.S. Department of Agriculture Page 7

Figure 10. Hog panel fencing. Figure 11. A feral swine is captured and fitted with a GPS collar to serve as a 

“Judas pig”, leading managers to other groups of feral swine.
eradicated. This is followed by a rapid management 

response when feral swine are detected to prevent future 

populations from becoming established. 

Environmental DNA (also known as eDNA) refers to DNA 

that is shed by an organism into the environment (e.g., 

water, soil, air). The genetic material could come from shed 

skin or hair, mucous, urine, or feces. Geneticists have 

developed a method for detecting feral swine eDNA in 

water sources. This method has been deployed 

operationally in several states, including New Mexico, to 

help locate feral swine, and may be particularly useful in 

large, remote areas where surveillance is difficult.

Recreational Hunting

While recreational hunting for feral swine is popular in 

many states, it is generally not considered an effective 

management option. Significant population reductions 

typically do not occur and feral swine behaviors or 

movements may be altered such that they impede other 

removal operations (e.g., trapping). Hunters usually target 

large males instead of females, which has little impact on 

overall population reduction. Additionally, recreational 

hunting creates incentives to maintain feral swine on the 

landscape and move feral swine to new areas for 

increased hunting opportunities, which has largely been 

attributed to the expansion of feral swine across the United 

States. Although controversial, several states have 

outlawed hunting in attempts to better manage feral swine 

populations. Research has shown that feral swine removal 

via hunting is often negated by the use of bait to attract 

feral swine. The supplemental food source increases 

fecundity and population growth despite hunter harvest. 

Hunting with Dogs

Hunting with dogs can be effective in certain 

circumstances, particularly in areas where feral swine 

densities are low or when trying to remove the last few 

remaining individuals of a population. However, it is best 

used in conjunction with additional management tools for 

large-scale removal efforts. This practice is also dangerous 

and of questionable ethics, given the frequently sustained 

injuries to dogs and feral swine prior to death. Dog owners 

should also be aware that their dogs are at high risk of 

exposure to pseudorabies if used to hunt feral swine in the 

United States.

Repellents

Considering the powerful olfactory senses of feral swine, 

repellents could be an effective nonlethal damage 

management tool, but have yet to be developed for 

operational use. Most repellents are only effective for a 

short amount of time as animals become habituated to 

them. 

Shooting

Aerial shooting is a common management tool that is most 

effective in open landscapes where feral swine densities 

are high (Figure 12). Helicopters are the most frequent 

type of aircraft used. As feral swine population densities 

decrease, the costs and efforts associated with aerial 

shooting increase. Therefore, additional removal methods 

as part of an integrated management program are advised 

when eradication or a significant population reduction is 

the goal. 

Advancements in technology have increased the 

effectiveness and affordability of thermal and night vision 

scopes for shooting feral swine at night from the ground or 

elevated platforms and may be particularly useful in areas 

Page 8 WDM Technical Series─Feral Swine

Figure 12. Aerial shooting of feral swine is commonly done in open landscapes. 
where feral swine are primarily active at night. However, 

little research has been done to evaluate its efficacy for 

large-scale removal efforts. Night shooting is legal in many 

states, but check local and state regulations to ensure 

compliance. In addition to removing some feral swine, 

night shooting has the added benefit of hazing nearby 

swine to keep them from damaging crops at night. 

Snares

Snares can be an effective lethal option under certain 

circumstances (Figure 13). Portability is a major advantage 

to using snares, particularly in inaccessible areas where 

corral or box traps are not feasible. Snares can also be 

advantageous when targeting particular individuals (e.g., 

feral swine accessing crop fields through a fence) or trapshy individuals, but are less effective for large-scale 

removal operations. Neck snares are most common and 

can be set under fences, on mud rub posts or trees, or 

along trails. Snaring regulations vary by state and must be 

followed accordingly.

Toxicants

An anticoagulant-based toxicant containing warfarin, 

known as Kaput® Feral Hog Bait, is registered by the U.S. 

Environmental Protection Agency (EPA), but is not yet 

approved for operational use on feral swine by any state. 

HOGGONE®, a sodium nitrite-based toxicant, is currently 

under research and development in the United States and 

will likely be submitted to the EPA for registration. Sodium 

nitrite causes a quick and humane death from 

methemoglobinemia (inability of blood to transport oxygen 

to organs and tissues). 

Researchers are also working to develop feral swinespecific bait boxes to restrict access to bait by non-target 

species and ensure the safe deployment of toxicants 

(Figure 14). 

Trapping

Trapping followed by lethal removal is one of the most 

commonly implemented control techniques. Relocation of 

trapped feral swine is not recommended as it moves the 

problem elsewhere, may facilitate the spread of disease, 

and is illegal in most states. Trapping success varies 

seasonally and is most effective when natural food 

resources are limited. The type of trap, trigger, and door, as 

well as trap placement in high-use areas, and ample prebaiting also influence trapping success. Corral and box

U.S. Department of Agriculture Page 9

Figure 13. A snare set for feral swine. Snaring regulations vary by state and 

must be followed accordingly.

Figure 14. USDA researchers have designed feral swine-specific bait stations. The bait 

station’s lids take advantage of swine rooting behavior. Feral swine can lift the heavy, 

magnetized lids, but many non-target species cannot. 
traps are the most commonly used trap types (Figure 15). 

Corral traps are larger than box traps, allowing a greater 

number of feral swine to be captured at once, and are 

generally more effective. Box traps are more portable 

which may be beneficial in more inaccessible areas. 

Corral Traps

Corral traps are typically constructed with 5 to 6.5 ft (1.5 to 

2 m) high galvanized wire livestock panels or custom built 

trap panels that fit together securely (Figure 15). Trap 

panel wire spacing varies and each type has pros and 

cons. Panels with 4 in x 4 in (10 cm x 10 cm) wire spacing 

are lighter and less expensive, but allow piglets to escape. 

Comparatively, panels with 2 in x 4 in (5 cm X 10 cm) wire 

spacing prevent piglets from escaping, but are 

substantially heavier and more expensive. A lighter option 

that still retains piglets includes panels with graduated 

spacing, where spacing is smaller towards the bottom and 

increases in size towards the top. A 4- or 5-panel corral 

trap is generally recommended, as trap-wary feral swine 

might be hesitant to enter a trap any smaller. Corral traps 

are most commonly constructed in a circular design with 

panels secured to T-posts around the perimeter of the trap.

Box Traps

Box trap designs vary but are often 4 ft x 4 ft x 8 ft (1.2 m x 

1.2 m x 2.4 m) and consist of a welded angle iron frame 

Page 10 WDM Technical Series─Feral Swine

with a door on one side and wire panels covering the top, 

bottom, and sides (Figure 15). Commercially manufactured 

box traps are available. If the floor of a box trap has wire 

paneling, cover it with dirt to reduce trap shyness by feral 

swine. 

Drop Traps

Drop traps consist of a corral trap suspended 

approximately 3 to 4 ft (0.9 to 1.2 m) off of the ground. It 

drops when triggered, eliminating the need for a gate 

(Figure 16). This trap style may increase capture success 

when feral swine are reluctant to enter a trap through a 

gate.

Trap Gates

There are a variety of designs to choose from, but trap 

gates are generally grouped into 3 categories: guillotine, 

rooter, and saloon (Figure 17). Guillotine gates drop 

straight down from above when activated. Rooter gates are 

a “continuous-catch” gate commonly constructed from 

steel tubing that is hinged at the top and set to close from 

above. They are similar to guillotine gates, but are angled 

towards the inside of the trap. This allows additional feral 

swine to root under the gate and enter the trap once the 

gate has been closed. Saloon gates are typically springloaded and hinged on the sides in order to swing closed 

when triggered. Wider gate doors (i.e., 5 to 8 ft (1.5 to 

Figure 15. Common corral trap (left) and box trap (right).
A trip wire and root stick are the two most common 

manual trigger types. The trip wire is set horizontally 

across the back of a trap approximately 16 to 20 in (41 

to 51 cm) above the ground and strung to a gate 

retention mechanism attached to the trap door (e.g., 

prop stick, pin). Bait is set behind the trip wire so feral 

swine must apply pressure to the trip wire in order to 

release the retention mechanism. Alternatively, a root 

stick is anchored horizontally by 1 or 2 set stakes 

secured into the ground to hold up the trap gate and 

surrounded by bait (Figure 18). The trap is then 

triggered when feral swine feed at the bait pile and 

inadvertently dislodge the root stick, which closes the 

trap.

Human-activated triggers may be as simple as a pull 

string attached to a gate with a person waiting in a 

nearby blind. More advanced systems allow for remote 

monitoring and activation from a cell phone or 

computer. There are several remote controlled systems 

on the market that provide excellent options to increase 

trapping efficiency and success (Figure 19). However, 

cost may be prohibitive, as these systems range from 

$2,000-5,000/system and require a monthly cellular 

service plan. Additionally, functionality of these systems 

may be limited in areas with poor cellular service.

2.4 m)) may increase capture success compared to 

smaller gate openings.

Trap Triggers

An array of different trigger types and designs exist, but 

triggers can generally be grouped into either manual (i.e., 

triggered by feral swine) or human-activated triggers. 

Manual triggers are usually less expensive, but humanactivated triggers prevent the capture of non-target species 

and allow for the desired number of feral swine to enter a 

trap before closing the gate. 

U.S. Department of Agriculture Page 11

Figure 17. Trap gates designs include a) guillotine, b) rooter, and c) saloon.

Figure 16. Drop trap.
Bait

An expansive list of bait has been used to trap feral swine, 

including various grains, peanuts, fish, and commercial 

livestock feed. However, dry or fermented whole-kernel 

corn is used most commonly. Olfactory attractants, such as 

strawberry jello or commercial scent products, may also be 

used. Bait attractiveness may vary by season and/or 

region. Feral swine-specific baits that reduce non-target 

consumption have not been identified. Always be sure to 

follow state baiting regulations, as restrictions in some 

states may occur. 

Page 12 WDM Technical Series─Feral Swine

Economics

Given their destructive nature, economic impacts of feral 

swine damage in the United States are extensive, but 

quantifying these impacts on a national scale can be 

difficult. A commonly reported and likely conservative 

annual estimate of damage and cost of feral swine control 

is $1.5 billion, based on an estimated 5 million feral swine 

in the United States that cause $300 of damage per 

individual. 

Agricultural damage alone is substantial. Damage 

estimates of approximately $390 per individual have been 

reported in areas with extensive agriculture. Feral swine 

damage to crops is estimated at $30 million annually in 

Alabama. Corn, wheat, rice, soybeans, sorghum, and 

peanut damage in 11 states including Florida, Mississippi, 

and Texas was estimated at $190 million per year. 

Damage to pastureland from feral swine rooting is also 

prevalent, with estimates at $9.9 million in hay loss and 

$2.5 million in repairs to pastureland in Louisiana. 

Additionally, timber loss due to feral swine damage in 

Tennessee and Louisiana is estimated to be $1.5 million 

per year. 

Disease transmission from feral swine to domestic 

livestock represents a potential threat that could lead to 

significant economic impacts, particularly from the spread 

of foreign animal diseases (e.g., African swine fever, 

classical swine fever, foot-and-mouth disease). Estimates 

suggest a foot-and-mouth disease outbreak in the United 

States would cost from $13.6 to $20.8 billion in the first 

year alone. Losses over a 5-year period may reach $2.6 to 

$4.1 billion if a classical swine fever outbreak were to 

occur. Additional livestock-related economic impacts, such 

as predation, have not been estimated. 

Although financial losses due to feral swine damage are 

substantial, feral swine also provide some economic 

benefits. Feral swine hunting generates approximately 

$1.2 million annually for California, where feral swine are 

considered a game animal. Additionally, feral swine are 

sold to meat markets in Louisiana, Florida, and Texas to be 

used in restaurants or pet food for upwards of $0.40 per 

Figure 18. Root stick trigger design.

Figure 19. Remote controlled trap trigger.
highly variable among feral swine populations, averages 

typically range between 150 to 220 lbs (70 to 100 kg), 

and rarely exceed 550 lbs (250 kg).

Several characteristics can be used to distinguish males 

from females. Males tend to be 1.2 to 1.4 times larger 

than females. They also have a thick tissue layer under 

the skin surrounding the lateral portion of their 

shoulders for protection while fighting for breeding 

opportunities. This is commonly known as a “shield” 

and increases in size with maturity. Permanent canines 

in males are also significantly larger and the upper 

canines grow upward. The upper canines of females 

grow downward. 

Range

Feral swine were originally introduced and relatively 

confined to coastal regions of the southeastern United 

States and California beginning in the early 1500s, but 

the range of feral swine has increased substantially 

over the last several decades across all major 

geographical regions of the United States (Figure 2). 

Recently reported in up to 48 states, feral swine have 

since been eradicated or thought to be removed from 

11 states (Colorado, Idaho, Illinois, Iowa, New Jersey, 

New York, Maine, Maryland, Minnesota, Washington 

pound (lb) ($0.88/kilogram (kg)). Landowners generate 

income by charging hunting fees for feral swine on their 

land and there is a well-established commercial trapping 

industry for feral swine. However, these examples often 

complicate management by providing incentives to 

maintain feral swine on the landscape and rarely outweigh 

the negative impacts. 

Species Overview

Identification

A single species, Sus scrofa, constitutes all feral swine 

currently found in North America. Domestic pigs and 

Eurasian wild boar are considered the same species 

because the Eurasian wild boar is the ancestor to all 

domestic breeds. The species is classified by three main 

types: 1) domestic pigs that became feral, 2) Eurasian wild 

boar, and 3) hybridization between feral domestic pigs and 

wild boar. However, most feral swine populations in the 

United States are characterized by varying degrees of 

hybridization between feral domestic pigs and wild boar. As 

a result, characteristics often vary regionally or locally, 

depending on the ancestral origins of the feral swine. 

Physical Description

Feral swine have a stout, barrel-shaped body, short legs, 

short and stocky neck, and long, pointed head. They have 

small eyes and large ears that are pointed at the tip. Their 

tail is short, generally covered in hair, and may be straight 

or curled. Keratinized hooves cover 4 toes on each foot, 

with 2 lateral toes, or dew claws, located higher on each 

leg. The density of coat hair varies, but is typically coarse 

and bristled. Coat coloration is highly variable, from 

different shades of black, white, or red-brown in a solid, 

spotted, mottled, or grizzled pattern (Figure 20). Grizzled 

patterns are characterized by light brown to black hair with 

white or tan tips and are mainly expressed in feral swine 

with predominantly wild boar ancestry. Piglets are often 

characterized by a striped pattern for the first 4 to 6 

months after birth (Figure 21). While body mass may be 

U.S. Department of Agriculture Page 13

Figure 20. Feral swine coat coloration varies.
and Wisconsin). However, continued control and 

management is crucial to prevent further spread of feral 

swine. Recent research has predicted that without 

intensive control feral swine have the potential to become 

established across much of the United States in the next 3 

to 5 decades (Figure 22). Currently, feral swine are 

Page 14 WDM Technical Series─Feral Swine

sporadically dispersed in relatively low numbers across 

much of the western, northeastern, and north-central 

United States, but are found in high concentrations across 

the majority of the southeastern region, California, Texas, 

and Oklahoma. 

Voice and Sounds

Feral swine use a variety of vocalizations, including 

contact, nursing, and feeding grunts, squeals, growls, and 

teeth clacking. Females and piglets tend to be more vocal 

than males. Numerous scent glands (e.g., metacarpal, 

preputial, tusk, preorbital) are also used for 

communication, generally during reproductive activities. 

Tracks and Sign

Numerous signs can be used to determine the presence of 

feral swine in an area, including rooting, wallows, rubs, 

tusking, beds, and farrowing nests. 

Figure 21. Striped piglets.

Figure 22. Models predict that the range of feral swine in the United States would expand dramatically over the next 30 to 50 years without intensive 

management and control. Counties in red represent areas that have been or are highly susceptible to feral swine invasion. Counties in blue 

represent areas that are least susceptible to invasion. Black points indicate the 2012 range of feral swine.
Feral swine tracks are commonly confused with other 

ungulate species, primarily white-tailed deer. However, 

feral swine tracks tend to have more rounded or blunt tips 

with an overall squared or rounded shape, and tracks are 

often found in conjunction with other sign (Figure 23a).

Feral swine scat is primarily in the form of segmented 

clumps that are irregularly shaped (Figure 23b). 

Appearance and size will depend on the diet and size of 

the animal, respectively. 

Rooting is a foraging method used by feral swine to 

excavate subterranean food. While rooting is most 

common in winter and spring, it occurs on a year-round 

basis in a variety of habitats, often based on food 

availability. 

Wallows may be natural mud depressions or are created 

via rooting. They are often filled with water and are typically 

found in wet areas that feral swine use for 

thermoregulation, especially in the summer (Figure 5). 

Feral swine wallow to reduce their body temperature 

because they lack sweat glands. It also helps to protect 

them against ectoparasites, such as ticks and fleas. Muddy 

vegetation and rubs are common in areas surrounding 

wallows. Feral swine rub excess mud, hair, and 

ectoparasites on trees, fence posts, logs, utility poles, or 

creosote-soaked poles (Figure 23c). 

Tusking occurs when feral swine cut a tree with their tusks 

to release the tree’s sap. Feral swine rub themselves in the 

sap in order to protect themselves from ectoparasites. 

Beds and farrowing (birthing) nests are typically found in 

dense vegetation or cover and often appear similar, but 

farrowing nests are generally larger and lined with leaves, 

vegetation, or grass (Figure 24). During the winter in 

northern regions of the United States, feral swine build 

nests with vegetation, such as cattails (Typha spp.), in 

wetlands often referred to as “pigloos.” 

Reproduction

Feral swine are extremely prolific breeders with a high 

reproductive potential, capable of breeding as early as 6 to 

12 months of age. They can breed and farrow year round 

U.S. Department of Agriculture Page 15

Figure 23. In addition to rooting and wallowing sites, common feral swine sign include a) 

tracks, b) scat, and c) rubbings on trees or fence posts.

because they are polyestrous. However, seasonal peaks 

have been reported in the spring and fall, when forage 

resources are typically more abundant. Availability of hard 

mast and other quality forage significantly influences feral 

swine reproductive success.

(a) 

(b) 

(c) 
The average litter size is approximately 5 piglets, and 

ranges from 1 to 12 piglets. Average gestation length is 

112 to 120 days. Multiple litters per year are possible, with 

reports of sows breeding within 1 month of farrowing, but 

this is often limited based on resource availability. Sows 

build a farrowing nest shortly before giving birth and piglets 

stay in or near the nest for approximately 3 weeks after 

birth. 

Mortality

Few studies have been conducted in the United States to 

quantify the specific causes of feral swine mortality. 

Anthropogenic mortality, including recreational hunting and 

population management efforts, is likely the most 

significant source of mortality, Although increased mortality 

for feral swine less than 1 year of age has been observed 

in other parts of their invasive range, this has not been 

consistently observed in the United States. Natural 

mortality may be caused by diseases, parasites, accidents 

Page 16 WDM Technical Series─Feral Swine

(e.g., piglets crushed in a farrowing nest or trampled by 

adults), starvation, or predation. Predation is a small 

percentage of overall feral swine mortality. Common 

predators include coyotes, bobcat (Lynx rufus), black bear 

(Ursus americanus), and mountain lions (Puma concolor), 

but predation on adult feral swine is predominately 

restricted to black bears and mountain lions. Feral swine 

often live up to 8 years, but rarely past 10 years. 

Habitat

Feral swine are an adaptable species, capable of surviving 

nearly anywhere across the United States. Habitat 

selection is based upon locally available habitat types and 

varies seasonally, but is primarily driven by the need for 

ample food, water, and cover. Feral swine have a particular 

inclination towards water, especially in arid regions, and 

habitat types that readily accommodate this resource (e.g., 

wetlands, swamps, riparian areas, marshes) are used 

extensively. 

Feral swine in the southeastern United States commonly 

inhabit bottomland hardwoods, drainage corridors, 

marshes, sloughs, forested swamps, and mesic hardwood 

forests. In the south-central United States, feral swine 

prefer riparian and upland areas with an abundance of 

water, mast, agriculture, or other resources. Comparatively, 

mixed forest-agriculture, scrub-shrub wetlands, cattail 

marshes, and spruce (Picea spp.) and fir (Abies spp.) 

forests are preferred habitats of feral swine in the 

northeastern United States. In western states, oak 

woodlands and grasslands, chaparral scrublands, and 

northern coastal sage are preferred.

Behavior

Feral swine are social animals, usually found in matrilineal 

(based on kinship with the mother) groups known as 

sounders. A typical sounder consists of one or several sows 

and their young, with group sizes ranging from 2 to 30, 

sometimes more, often fluctuating in size and composition. 

Juvenile males will travel in bachelor groups, whereas adult 

males are primarily solitary except when with sounders for 

breeding purposes. Limited research suggests territoriality 

among sounders may exist, which may be particularly 

Figure 24. Feral swine nest made of grass.
upon available resources. Rooting is a common foraging 

method used by feral swine to access subterranean 

food resources (e.g., roots, bulbs). Hard mast (primarily 

acorns) are an important seasonal food source. Feral 

swine readily consume an extensive list of agricultural 

crops, including corn, wheat, soybeans, peanuts, rice, 

potatoes, pumpkins, grapes, pecans, and berries, that 

varies by region (Figure 25).

Feral swine eat animal matter as well, but usually to a 

much lesser extent. Consumption of animal matter is 

typically opportunistic, but intentional predation may 

also occur. Common animal matter includes 

earthworms, insects, crustaceans, small mammals, 

amphibians, reptiles, and birds. Predation of whitetailed deer fawns and young domestic livestock has 

been reported, but most large mammal consumption is 

in the form of carrion. 

evident in areas with a high density of feral swine and low 

abundance of resources. 

Both diurnal and nocturnal activity is common, but feral 

swine subject to repeated control efforts or recreational 

hunting are usually more nocturnal. Seasonal variations in 

temperature also cause shifts in daily activity (i.e., 

increased nocturnal activity during the summer and diurnal 

activity in the winter), likely as a way to regulate body 

temperature. Feral swine may also increase activity during 

the day in areas with thick vegetation. 

Feral swine primarily restrict daily movements to relatively 

short distances. The average hourly distance moved is 

approximately 0.2 to 0.3 miles (0.35 to 0.42 kilometers 

(km)) with a maximum of 0.5 to 1.3 miles (0.8 to 2.1 km). 

However, large-scale movements do occur (e.g., when 

adult males are searching for breeding opportunities or in 

areas where food or water resources are limited). 

Relatively unpressured feral swine (i.e., those exposed to 

minimal control efforts or recreational hunting) can usually 

be tracked as they consistently use the same trails and 

bedding areas. Feral swine movement in response to 

management pressure varies. For example, feral swine 

have been reported to increase their space-use and 

movements following repeated management operations. 

They may also disperse outside of their home range during 

aerial gunning operations, but often return to normal 

movement patterns shortly thereafter.

There is considerable variation in feral swine home range 

size which is influenced by numerous factors, such as 

resource abundance, feral swine density, habitat type, 

season, climate, sex, and age. The average home range 

size is approximately 4.8 miles2 (12.4 km2), but has been 

reported to exceed 19.3 miles2 (50 km2). Male home range 

size may be up to 2 miles2 (5 km2) larger than female 

home range size. 

Food Habits

Feral swine are opportunistic omnivores but primarily feed 

on plant matter. Leaves, stems, fruits, and seeds are 

selectively eaten relative to plant phenology and nutritional 

quality. Specific diets vary regionally and seasonally, based 

U.S. Department of Agriculture Page 17

Figure 25. Aerial view of feral swine damage to a corn field in Texas.
Legal Status

There is a complex legal and political network surrounding 

the issue of feral swine in the United States. As such, laws 

and policies vary from state to state. Feral swine are 

generally classified as an invasive species, nuisance 

animal, or similar variation in most states. Feral swine are 

listed as a game animal in California, Alabama, West 

Virginia, Ohio, and Hawaii, which has created a socioeconomic challenge for management and provides an 

incentive to sustain populations of feral swine within those 

states. Numerous states have outlawed feral swine 

transportation, but transportation following varying 

guidelines is still permitted in many other states (e.g., 

Alaska, Florida, Georgia, Mississippi, North Carolina, 

Oklahoma, Texas), despite the fact that the humanmediated movement of feral swine has been a primary 

factor in their expansion.

Page 18 WDM Technical Series─Feral Swine

Although high-fenced shooting operations for feral swine 

are becoming more restrictive, they are still permitted in 

several states, including Texas, Pennsylvania, and Iowa. 

Furthermore, feral swine meat markets are legal in Florida, 

Texas, and Louisiana. A full spectrum of hunting 

regulations also exist depending on the state. For example, 

there are no seasons, and night shooting with night vision 

or thermal equipment is permitted in Texas. Conversely, 

public hunting has been banned in several states (e.g., 

Kansas, New York, North Dakota, South Dakota) or 

restricted to incidental take during seasons for other game 

species as a management strategy to de-incentivize the 

establishment of feral swine populations for hunting. 

Increased efforts to inform state and federal policy makers 

about the risks associated with feral swine ensures 

science-based laws and regulations are enacted to aid in 

the reduction of feral swine populations and associated 

damage.
U.S. Department of Agriculture Page 19

Acknowledgements

Figure 1, 3-25. Photos and map by USDA-APHIS-Wildlife Services

Figure 2. Map by the Southeastern Cooperative Wildlife Disease Study Program

We thank Scott Alls, Parker Hall, and Dana Johnson for providing critical reviews of this manuscript. 

Glossary

Aerial Shooting: A lethal removal method where a 

professional marksman shoots feral swine from a 

helicopter or fixed-wing airplane. 

Boar: A male feral swine. 

Corral Trap: A type of trap used to catch feral swine that is 

typically circular in shape and large enough to capture 

numerous individuals at once. 

Farrowing: The act of giving birth to feral swine piglets. 

Omnivore: An animal that eats both animals and plants.

Piglet: A feral swine less than 6 months old.

Polyestrous: An animal that has multiple estrous cycles 

per year. 

Sounder: A group of feral swine typically consisting of one 

or several related sows and their offspring.

Sow: A female feral swine.

Keywords

Agricultural damage, Damage management, Disease, 

Eurasian wild boar, Feral swine, Rooting, Monitoring, 

Sounder, Aerial shooting, Sus scrofa, Toxicants, Trapping, 

Wallow, Wild Pig, Wildlife Damage Management

Citation

Glow, M.P., K.C. VerCauteren, and N.P. Snow. 2020. Feral 

Swine. Wildlife Damage Management Technical Series. 

USDA, APHIS, WS National Wildlife Research Center. Fort 

Collins, Colorado. 21p.

Disclaimer

Wildlife can threaten the health and safety of you and 

others in the area. Use of damage prevention and control 

methods also may pose risks to humans, pets, livestock, 

other non-target animals, and the environment. Be aware 

of the risks and take steps to reduce or eliminate those 

risks. 

Some methods mentioned in this document may not be 

legal, permitted, or appropriate in your area. Read and 

follow all pesticide label recommendations and local 

requirements. Check with personnel from your state 

wildlife agency and local officials to determine if methods 

are acceptable and allowed. 

Mention of any products, trademarks, or brand names 

does not constitute endorsement, nor does omission 

constitute criticism. 
Page 20 WDM Technical Series─Feral Swine

Resources

Hamrick, B., M.D. Smith, C. Jaworowski, and B. Strickland. 2016. A landowner’s guide for wild pig management: Practical 

methods for wild pig control. Publication 2659. Mississippi State University Extension Service, Alabama Cooperative 

Extension System. 54p.

Mayer, J.J. and I.L. Brisbin, Jr., editors. 2009. Wild Pigs: Biology, damage, control techniques, and management. SRNL-RP2009-00869. Savannah River National Laboratory, Aiken, South Carolina, USA.

Pedersen, K., C.T. Turnage, W.D. Gaston, P. Arruda, S.A. Alls, and T. Gidlewski. 2018. Pseudorabies detected in hunting dogs 

in Alabama and Arkansas after close contact with feral swine (Sus scrofa). BMC Veterinary Research 14: 388. doi: 

10.1186/s12917-018-1718-3

Snow, N.P., M.A. Jarzyna, and K.C. VerCauteren. 2017. Interpreting and predicting the spread of invasive wild pigs. Journal 

of Applied Ecology 54:2022-2032. 

VerCauteren, K.C., J.C. Beasley, S.S. Ditchkoff, J.J. Mayer, G.J. Roloff, and B.K. Strickland, editors. 2020. Invasive wild pigs in 

North America: Ecology, impacts, and management. CRC Press, Taylor & Francis Group, LLC, Boca Raton, Florida, USA.

West, B.C., A.L. Cooper, and J.B. Armstrong. 2009. Managing wild pigs: A technical guide. Human-Wildlife Interactions 

Monograph 1:1-55.
Appendix 

Page 21

Damage Management Methods for Feral Swine

 

 

Type of Control 

 

Available Management Options 

Fencing • 2-strand, polywire electric fence

• Galvanized wire mesh fence

• Hog panel fence

Fertility Control None currently available

Frightening Devices Loud noises and flashing lights have been used with limited success

“Judas Pigs” Capturing and radio-collaring an individual feral swine, then tracking it as it returns to its sounder or 

another group of feral swine. The entire group can then be removed using a variety of methods. 

Monitoring • Trail cameras

• Environmental DNA

Repellents None currently available

Shooting Regulations vary by state

• Aerial shooting

• Thermal and night vision equipment

• Hunting with dogs

Snares Neck snares placed under fences, on mud rub posts, or trees or along trails.

Toxicants • Kaput® Feral Hog Bait; Registered for use by EPA, but not approved by states 

• HOGGONE® sodium nitrite bait; Under development 

Trapping Regulations vary by state

• Corral trap

• Box trap

• Drop trap