FERAL SWINE: Damages, Disease Threats, and Other Risks

What Are Feral Swine?

Feral swine (also called wild pigs, Eurasian boar, or feral 

hogs) are a harmful and destructive invasive species. 

They are not native to North America. Early explorers 

and settlers first brought feral swine into the United 

States in the 1500s as a source of food. The number of 

feral swine grew further after that; they were introduced 

repeatedly in different areas of the country and also 

started crossbreeding with escaped domestic pigs. Today, 

approximately 6 million feral swine can be found across 

more than 31 States.

Feral swine can carry at least 30 diseases and nearly 40 types of parasites that may affect 

people, pets, livestock, and wildlife. Some diseases, such as pseudorabies, are fatal 

to cats and dogs that may be exposed from direct contact with a feral swine carcass. 

Feral swine can also transmit foodborne illnesses, such as E. coli, toxoplasmosis, and 

trichinosis. In some areas, feral swine have been the cause of elevated waterborne 

bacteria levels in streams and irrigation canals, which is another risk for human health. 

When in roadways or at airports, feral swine can collide with vehicles and aircraft, putting 

the safety of drivers, pilots, and passengers at risk. Other public safety risks arise when 

feral swine are in urban and suburban areas. As they become less afraid of people over 

time, they have shown aggression toward golfers, picnickers, and others. This behavior 

is more of a problem when they associate people with food because of handouts and 

improper waste disposal. In addition, feral swine may be aggressive to dogs and other pets.

Feral swine damage crops and destroy fields (reducing crop yield) with their feeding, rooting, 

trampling, and wallowing behaviors. They usually target sugar cane, corn, grain sorghum, wheat, 

oats, peanuts, and rice, among others. Vegetable and fruit crops, such as lettuce, spinach, melons, 

and pumpkins, are also attractive to them. Feral swine can also impact the regeneration of forests. By 

consuming seeds, nuts, and seedlings and damaging land, they keep new trees from growing and can 

stunt the growth of existing trees.

Feral swine can spread diseases to livestock. This causes economic losses such as decreased 

production, reduced feed efficiency (less food intake affects animal growth and overall health), lower 

reproductive success and increased mortality in the herd, and higher costs for veterinary care. Feral 

swine are omnivorous, meaning they eat just about anything. They can kill calves and lambs, and adult 

livestock are vulnerable to predation while giving birth. 

In addition, feral swine degrade pasture grasses; eat, contaminate, and destroy livestock feed; and 

damage farm property, such as fences, water systems, irrigation ditches, troughs, and levees.

Why Are They a Problem?

The damage feral swine cause is wide-ranging and far-reaching. With 

populations throughout the United States, this invasive animal—with 

few natural predators—negatively impacts everything from agriculture 

and the environment to human health and public safety. Feral swine can 

multiply faster than any other large mammal; females begin breeding at 

about 8 months and can produce 2 litters of 4–12 piglets every 12–15 

months. The main reasons for their expanded range include accidental 

escapes or intentional releases from fenced facilities and people moving 

them illegally to new areas. Damages, costs, and risks from feral swine 

will only keep rising if their populations continue to expand.

Health and Public Safety

Agriculture

Animal and Plant Health Inspection Service
Feral swine cause widespread damage to natural resources. 

They consume large amounts of vegetation; destroy 

plants with their rooting, soil compaction, and wallowing 

behaviors; and in some areas, may eat or uproot protected, 

sensitive, unique, or rare plants. Often, the damaged 

land then becomes vulnerable to erosion and non-native, 

invasive plants. 

In addition, soil disturbance and vegetation loss from feral 

swine damage increases erosion and degrades water quality. 

Siltation (a form of water pollution) and contamination in 

streams and coastal areas with swine activity have contributed 

to declines in aquatic organisms, including freshwater mussels 

and insects. 

Wildlife are impacted by feral swine, too. Since their diets 

overlap, feral swine and native wildlife end up competing 

for important and limited natural food sources, such as 

acorns and other forest tree nuts. Feral swine also reduce the 

amount of food available in general—they consume seeds, 

plants, and small animals (including insects, earthworms, 

Natural Resources

FERAL SWINE: Damages, Disease Threats, and Other Risks

If feral swine are in the area, they can quickly ruin homeowners’ efforts to maintain and improve 

their properties. Destroyed vegetation and wallows reduce the aesthetic value of private 

properties, as well as public parks and recreational areas. Feral swine foraging, rooting, and 

wallowing also damages landscaping, golf courses, recreational fields, cemeteries, parks, lawns, 

and other natural areas. 

In addition, adult feral swine weigh from 75 to 250 pounds on average, with some weighing 

considerably more. As a result, collisions with vehicles and aircraft can mean costly property damage.

Property

Other resources affected by feral 

swine include national historic sites, 

tribal sacred sites and burial grounds, 

cemeteries, and archaeological 

sites and digs. Feral swine damage 

structures, destroy vegetation, and 

disturb soil and land. This can seriously 

degrade the significance and historic 

integrity of these sites. Foraging and 

habitat damage by feral swine can also 

negatively impact the distribution and 

abundance of plants and animals that 

may be used for traditional purposes 

(for example, sage for Native American 

ceremonies or herbal medicines).

Cultural and Historic Resources

voles, shrews, turtles, amphibians, 

and ground-nesting birds). Feral 

swine will destroy nests and eat the 

eggs of alligators, other reptiles, 

and ground-nesting birds, such 

as quail, turkey, and shorebirds. 

And because feral swine prefer 

wet environments, they compete 

with native wildlife for scarce water 

resources during dry seasons. Feral 

swine can also have negative effects 

on threatened and endangered 

species and their habitats. 

Lastly, feral swine can spread 

diseases to wildlife, some of which 

can be fatal. The damage they 

cause also tends to increase mosquito habitat; this, in turn, can increase the 

prevalence of avian malaria and avian pox, which threaten the health 

of native birds.

Want To Learn More?

Call the USDA-APHIS Wildlife Services 

program in your State at 1-866-4-USDA-WS

or go to www.aphis.usda.gov/wildlifedamage/stopferalswine to learn more 

about the problems caused by this

invasive animal, as well as to seek 

advice and assistance in dealing 

with feral swine.

The U.S. Department of Agriculture is an equal 

opportunity provider, employer, and lender.

Program Aid No. 2195b 

Revised May 2020