National Wildlife Research Center (NWRC)

Feral swine are an increasing problem in the United States and around the world. They destroy native vegetation, prey on wildlife and livestock, and transmit diseases to humans and livestock.

When responding to disease outbreaks, livestock owners, disease experts, and natural resource managers often reduce infected or susceptible animals through culling. In the event of a catastrophic disease outbreak such as foot-and-mouth disease or classical swine fever, a means for containing free-ranging feral swine would be crucial to the safety of the U.S. livestock industry.

In the United States, current culling and population management techniques for feral swine include recreational harvest, aerial gunning, trapping, and snaring. NWRC researchers are working to improve existing tools and develop new tools for managing feral swine. These efforts include developing and registering an oral toxicant, investigating new trapping techniques, and studying feral swine movement and behavior.

Project Accomplishments

Oral Toxicant - In a continuing effort to find new management tools for use with feral swine, NWRC researchers are collaborating with Australian scientists in the development and registration of a new oral toxicant called HOG-GONE®, which contains lethal doses of sodium nitrite.

“Sodium nitrite may be the ‘Achilles Heel’ of feral swine because of their sensitivity to this substance relative to many other mammals,” notes NWRC’s research wildlife biologist Fred Cunningham. “Since we currently do not have any toxicants registered for use with feral swine in the United States, we’re very interested in evaluating its effectiveness here, but we’re also concerned about potential nontarget hazards.”

To better understand the relative sensitivities of feral swine, raccoons, and white-tailed deer to sodium nitrite, an NWRC scientist conducted oral gavage trials at the Kerr Wildlife Management Area in Texas. Results showed that raccoons were more sensitive and expired more readily than swine or deer after ingesting sodium nitrite. Deer were the least sensitive to it. Researchers believe the sensitivity of raccoons and white-tailed deer is such that they are at low risk of intoxication when sodium nitrite-based baits (i.e., HOG-GONE) are coupled with swine-specific delivery systems. Research continues on HOG-GONE with an emphasis on reducing nontarget risks and developing swine-specific delivery systems.

Trapping - Without an effective registered toxicant in place, trapping continues to be one of the primary methods for controlling feral swine. Currently, numerous trap designs are used to capture feral swine; however, until recently, drop nets have not been evaluated. In a study conducted in Oklahoma between 2010 and 2011, NWRC scientists compared the effectiveness and efficiency of a drop net and a traditional corral trap for trapping feral swine. A mark and recapture analysis showed more swine were removed with drop nets than with corral traps. Efficiency estimates for the average time per capture were 1.9 hours for drop nets and 2.3 hours for corral traps. Feral swine did not appear to exhibit trap shyness around drop nets, which often allowed the researchers to capture entire family units in a single drop. The use of drop nets also eliminated the capture of nontarget species. The results of this study indicate that drop nets are an effective tool for capturing feral swine.

Movement and Behavior - It is important to consider how feral swine respond to control operations when developing optimal management plans. To better understand feral swine behavior, NWRC scientists studied the effects of baiting on feral swine movements and the likelihood that baiting would reduce swine dispersal under culling pressure on the Rob and Bessie Welder Wildlife Foundation (WWF) in San Patricio County, TX. By placing global positioning system collars on feral swine, scientists were able to track their movement throughout control operations. Population-wide culling activities included trapping and shooting around a centralized bait station. Feral swine home ranges did not differ between the bait station site and other non-baited sites. However, the daily movement rates of feral swine at bait station sites were 39 percent greater than the movement rates of animals in non-baited areas.

“Opposite to what we thought might occur, baiting stations did not reduce movement in our treatment areas,” states NWRC research wildlife biologist Fred Cunningham. “We do not recommend the use of baiting as an alternative to fencing for containing feral swine during culling activities.”

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