In November, the U.S. Department of Agriculture’s Animal & Plant Health Inspection Service (APHIS) accomplished two key tasks as part of its efforts to evaluate a toxic oral bait for use with invasive feral swine.

First, on Nov. 6, APHIS Wildlife Services (WS) received an experimental use permit (EUP) from the Environmental Protection Agency to conduct field trials of sodium nitrite toxic bait on free-roaming feral swine in Texas and Alabama. Second, on Nov. 20, APHIS signed a final environmental assessment and issued a "Decision & Finding of No Significant Impact" (FONSI) associated with conducting such field trials. Copies of the final environmental assessment and FONSI can be accessed at https://www.regulations.gov/docket?D=APHIS-2017-0067.

“Wildlife Services takes the selection and use of toxic baits for use in wildlife damage management very seriously. The final environmental assessment, FONSI and EUP are the result of years of collaborative research by WS and multiple private, state, federal and international partners,” WS deputy administrator Bill Clay said. “With these in place, we can now begin field trials to help determine the effectiveness of the sodium nitrite toxic bait for removing feral swine sounders in natural settings as well as any potential impacts to non-target wildlife.”

The EUP allows WS researchers to partner with landowners to identify and target three to nine feral swine sounders (i.e., social groups containing adults and juveniles) each in Texas and Alabama. APHIS said bait delivery systems designed to prevent access by non-target wildlife will be filled with placebo bait, which will be placed in the sounders’ territories and monitored with motion-activated cameras. Following a period of acclimation to confirm that feral swine are using the baiting areas, the placebo bait will be replaced with sodium nitrite toxic bait for two nights.

Furthermore, APHIS said at least 30 feral swine and no more than 30 raccoons in each state’s study area will be live captured and radio-collared prior to baiting in order to monitor their movements and exposure to the bait.

Landowners within 300 m of bait stations will be notified, and signs will be placed on bait stations and along roads leading into the study areas.

Sodium nitrite is a meat preservative commonly used to cure meats such as sausage and bacon. When eaten in high doses over a short period of time, it is toxic to feral swine. The mode of death is similar to carbon monoxide poisoning. Once feral swine eat enough sodium nitrite bait, they will get faint, rendered unconscious and quickly die, APHIS said. In most cases, feral swine die within 2.5-3.0 hours after eating a lethal dose.

Many factors are considered when developing a toxic bait for feral swine. It must be not only effective and humane in eliminating feral swine but also low risk for those handling it, the environment and wildlife, APHIS said. Other wildlife — such as raccoons, bears and deer — may be attracted to the sodium nitrite toxic bait, the agency noted, adding that, to prevent non-target species from accessing the bait, WS researchers will use delivery systems and baiting strategies designed for feral swine.

Trials will not be conducted in areas with known black bear populations.

Feral swine (also called wild pigs, Eurasian boar or feral hogs) are a harmful and destructive invasive species causing damage and disease threats to crops, public property, native ecosystems, livestock health and human health, APHIS said. There are more than 6 million feral swine in at least 35 states across the U.S. Their damages to agricultural crops alone are estimated at $190 million each year.

“Although trapping, aerial operations and recreational hunting of feral swine have effectively reduced damage in some areas, studies show that at least 70% of feral swine must be removed each year in order to prevent population growth,” Clay said. “Should the U.S. Environmental Protection Agency approve the toxic bait for use with feral swine, it could become another tool in the toolbox for integrated feral swine damage management.”

The development of tools and techniques for use in feral swine damage management supports the National Feral Swine Damage Management Program — a nationally coordinated effort among federal, state, tribal and local entities to manage feral swine damage and stop their spread.

More information about the sodium nitrite toxic bait for feral swine is available in this fact sheet.