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, their geographic 

range is quickly expanding as their populations continue increasing 

nationwide. Over 6 million feral swine can now be found across 

more than 35 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 spreading 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 expanding 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 as their populations continue to expand across the country.

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, voles, shrews, 

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

turtles, amphibians, and groundnesting birds). Feral swine will 

destroy nests and eat the eggs of 

alligators, other reptiles, and groundnesting 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?

Wildlife Services, part of the U.S. Department 

of Agriculture’s Animal and Plant Health 

Inspection Service, is on the front lines in 

the battle with this invasive animal. 

If you have questions or need help dealing 

with feral swine, call us at 1-866-4USDA-WS or go to 

www.aphis.usda.gov/wildlife-damage/stopferalswine. 

The U.S. Department of Agriculture is an equal opportunity provider, 

employer, and lender.

Program Aid No. 2195b 

Issued April 2016