Interpretive Summary: Impacts of Feral Swine on Rangeland Livestock Grazing Operations

By: Mark S. Thorne, Ph.D. | Specialist, Range and Livestock Management | University of Hawaii-Manoa, Cooperative Extension

Swine were introduced into the United States by early explores and settlers for food and it was not long after that feral populations became established from free-ranging animals and escapes from confinement. Then in the early 1900’s the Eurasian wild boar was introduced for sport hunting. Consequently, feral swine today are a mix of domestic pigs, Eurasian boars and hybrids of the two. 

Feral swine reproduce prolifically and are highly adaptable. Consequently, the feral swine population is rapidly expanding across the United States, including into western rangelands. Feral swine can be found in most if not all of Texas, Oklahoma, California and Hawaii, and parts of New Mexico, Arizona, Nevada, Utah, Oregon, and North Dakota. Altogether feral swine are present in 38 states and nationally there are an estimated 4-5 million head. Texas alone accounts for about 2.6 million head of feral swine. It is estimated that feral swine cause $1.5 billion annually in economic loss to agriculture, including the cost of control.  

Feral swine cause significant damage to the land and water they utilize and threaten the health and welfare of the wildlife, livestock, and humans they come into contact with.  In short, feral swine:

• Foul water sources utilized by native wildlife, livestock, and humans.
• Consume wildlife and plants to the point of jeopardizing their populations and health.
• Compete for food and habitat resources with native animals and livestock.
• Their rooting behavior causes disturbance that can lead to erosion and the establishment of weeds and consequently, compromise the productivity of rangelands, pastures, and farmland.
• They prey on young livestock (calves, kids, and lambs) and wildlife (deer fawns).
• They harbor at least 30 viral and bacterial diseases, such as swine brucellosis, pseudorabies, Tularemia, and tuberculosis that can infect livestock, other wildlife and humans.
• They also carry parasites that can be harmful to the livestock industry.

The control of local feral swine is generally accomplished through lethal removal (includes trapping, snaring, shooting and chasing with dogs) and exclusion fencing. No single action is a guarantee for successful control of feral swine and combinations of control measures are necessary to reduce or eliminate local numbers over time. Because feral swine are highly adaptive and learn to avoid threatening situations, successful control requires a strategy, patience and a knowledge of their behavior. Shooting and trapping are the most effective control methods, while nonlethal measures such as habitat manipulation, frightening devices, and guard animals, are ineffective.  

Without a significant effort by landowners and government agencies (state and federal lands) to control local populations, feral swine will continue to rapidly increase in numbers and extend their range to the detriment of rangelands, livestock and humans.