The invasive animals found in Illinois are officially classified as feral swine, though they are often mistakenly called “wild boar.” These animals pose a major threat to the state’s environment and agriculture due to their destructive nature and capacity to transmit disease. Illinois maintains a zero-tolerance policy, prompting a coordinated eradication effort by state and federal agencies to eliminate populations as soon as they are detected.
Feral Swine vs. True Wild Boar: Clarifying the Terminology
Agencies refer to the animals roaming Illinois as feral swine. This classification encompasses any unrestrained pig that has adapted to a wild existence, including escaped domestic livestock and their descendants. The term “true wild boar” refers to the pure Eurasian wild boar (Sus scrofa scrofa), a subspecies originally introduced to the United States for hunting.
Feral swine in the US are typically hybrid animals resulting from the interbreeding of domestic swine and Eurasian boar. These hybrids are the most common type found, combining the high reproductive rates of domestic pigs with the dense coats and tusks of the Eurasian boar. Agencies use the umbrella term “feral swine” because their ancestry is less important than their status as an invasive, non-native pest.
Current Presence and Geographic Distribution in Illinois
Feral swine are not established across Illinois in large, permanent territories, but their transient nature makes them a constant threat. Sightings were first documented in the early 1990s, primarily concentrated in the southern counties. As many as 32 counties have reported the presence of these animals, though many reports involve loose domestic pigs.
Confirmed self-sustaining breeding populations have historically been found in the forested and agricultural regions of central and southern Illinois, including Fulton, Fayette, and Marion counties. Their presence is often linked to borders with neighboring states like Missouri and Kentucky, where populations are more established, and along major river corridors. Control efforts prevent them from setting up permanent residence, ensuring local populations are temporary before removal.
Ecological and Agricultural Damage Caused by Feral Swine
The destructive habits of feral swine threaten Illinois’ agricultural industry and natural ecosystems. Their most recognizable damage comes from extensive rooting behavior, where they use their snouts to dig up soil in search of food. This activity destroys acres of planted crops, including corn and soybeans, and compromises soil stability, leading to increased erosion.
Wallowing in mud creates muddy pits that contaminate water sources and degrade water quality, impacting aquatic life. As omnivores, feral swine compete directly with native wildlife for resources like acorns and nuts. They also prey upon ground-nesting birds, reptiles, and amphibians, disrupting the local food web.
Feral swine also pose a threat to public health and livestock because they act as reservoirs for numerous pathogens. They carry over 30 diseases and 30 parasites, many transmissible to domestic livestock and humans. Diseases like pseudorabies and swine brucellosis are a concern for the commercial pork industry, as an outbreak could devastate herds and impact the state’s economy.
Illinois’ Strategy for Surveillance and Eradication
Illinois’ strategy focuses entirely on eradication, not population control or management for hunting. The Illinois Department of Natural Resources (IDNR) partners with the U.S. Department of Agriculture (USDA) Wildlife Services to achieve this zero-tolerance goal. This collaborative effort provides landowners with free assistance to identify and remove feral swine from their properties.
The most effective method employed is the use of large corral traps, designed to capture an entire social group, known as a sounder, at once. This whole-sounder removal is more efficient than shooting, which removes few individuals and causes the rest of the group to disperse, making them harder to track. Public hunting is discouraged because it teaches the animals to avoid humans and become nocturnal, complicating professional eradication efforts.
Feral swine are classified as non-game animals in Illinois. It is illegal to transport, release, or intentionally establish them. Landowners must obtain a nuisance wildlife permit from the IDNR to legally remove them outside of specific firearm deer seasons. This regulation prevents the animals from establishing a permanent, self-sustaining population.