Kyle Van Why & Tony Roland
USDA APHIS Wildlife Services (Pennsylvania)
Feral swine, also known as wild pigs, razorbacks, Eurasian boar, wild boar, or feral hogs, are not native to North America. They were first brought into the United States in the 1500’s by early explorers and settlers as a source of food. Repeated introductions occurred thereafter, as well as breeding with escaped pigs. They are a harmful and destructive invasive species whose geographic range is rapidly expanding and their populations are increasing across the US. Over 6 million feral swine can be found across more than 35 states. According to the Pennsylvania Game Commission, the term “feral swine” refers to any animal that is a member of the Family Suidae that is found roaming freely upon public or private lands within the Commonwealth. Feral swine were first observed in Pennsylvania in the late 1990’s and early 2000’s. The source of Pennsylvania’s feral swine is thought to be related to the numerous shooting preserves found throughout the Commonwealth and intentional releases for hunting, but has been supplemented by domestic livestock escapes. Because of the variable source populations, feral swine can be found throughout the Commonwealth, with isolated populations or single animals appearing and being eliminated annually. The true number of feral swine in Pennsylvania is unknown but thought by biologists to likely be a few hundred individuals mostly in Bedford and Fulton Counties.
The appearances of feral swine vary greatly from the dark brown color of a razorback to different shades of brown, black, red, white, pink, and spotted. Feral swine can exceed 400 lbs, but because of the diversity of lineages size is variable. Feral swine are able to reproduce at 6 months of age and females may have two litters a year with 3-12 young in a litter. Breeding potential is often dependent on local conditions and lineage, with animals having more domestic genes generally having more young. Additionally swine will breed year-round, so it is not uncommon for feral swine to have young in winter seasons. Feral swine often form family groups (sounders) and may consist of up to 15-20 individuals, usually comprised of sows and piglets, and occasionally juvenile males. Boars often roam independently searching out females to breed. Feral swine often have variable home ranges, with territories often defined by sounders and not individuals. Feral swine have few predators, but coyotes and black bears do predate on young piglets that can be separated from their mother. Feral swine may have large tusks that protrude from their jaw which aids them in rooting for food and defending themselves against predators. Feral swine wallow in shallow creeks, streams, marshes and other wet areas in an effort to keep cool and deter insects. Domestic swine that escape will often start to take on wild characteristics overtime depending on the breed, this includes increased hair growth and muscle structure changes. Over generations feral swine from domestic lineages will have variable colors and resemble traditional feral swine breeds.
Feral swine in the US inhabit many different habitat types from temperate forests to dry arid prairies. The only limiting factor is the proximity to a water source since pigs need to consume a quart of water for every pound of dry food they consume. In Pennslyvania, pigs utilize forests, fallow fields, agricultural fields, and wetland habitats to provide food, water, and cover during the different seasons. Feral swine typically prefer to bed down during the day in thick cover and become active at night.
Feral swine are a true omnivore, eating anything they encounter and exploiting any food source that is abundant. Feral swine have been documented eating a variety of food items including mast, grubs, tubers, carrion, reptiles, amphibians, and bird eggs, as well as agricultural crops including oats and corn. Feral swine are known to root up and eat grain seeds planted by farmers sometimes requiring farmers to replant fields multiple times a year. Feral swine feed by rooting up the soil while searching for grubs and seeds. Rooting causes substantial damage to fields, gardens, lawns, golf courses, and parks.
Feral swine are an invasive species that are highly prolific, are difficult to control in the wild, cause extensive damage to property, are extremely intelligent, and are known to carry over 30 diseases and 37 parasites that are transmittable to people, pets, livestock, and wildlife. The Pennsylvania Department of Agriculture is the state agency required to regulate shooting preserves including those containing swine. The Pennsylvania Game Commission is the state agency required to regulate feral swine in the wild. The US Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services is provided the authority to conduct the management and control of feral swine in the US. These agencies along with the Department of Conservation and Natural Resources work cooperatively to monitor and control the population of feral swine in Pennsylvania.