Feral swine do more than $1.5 billion a year in damage around the country, and scientists are taking what could be a big step toward controlling them.
They are field-testing poison baits made from a preservative that's used to cure bacon and sausage.
The tests will cover two major habitats where feral hogs are common during seasons when they're most likely to go for bait, said Kurt VerCauteren, feral swine project leader for the U.S. Department of Agriculture Wildlife Services. Tests will start early in 2018 in dry west Texas and continue in humid central Alabama around midsummer.
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The bait Vercauteren is working on uses the meat preservative sodium nitrite. It can keep an animal's red blood cells from pulling in oxygen. Pigs make very low levels of an enzyme that counteracts it, so it's more deadly to them than to humans or most domestic animals. Swine that gobble up enough sodium nitrite show symptoms similar to carbon dioxide poisoning: They become uncoordinated, lose consciousness and die within 90 minutes after eating it.
The prospect of a new way to fight the beasts is good news to Samuel "Sammy" Williams, who farms about 2,000 acres (3,220 hectares) of cotton, corn and peanuts in Alabama near Georgia and Florida.
Williams said he's killed nearly 200 feral hogs a year for the past four years, but those that survived still damaged his crops. Swine love corn and peanuts and will root up cotton fields for weed tubers, he said. They also make "wallow holes" 4 to 6 feet (1.2 to 1.8 meters) across -- though communal wallows can be much bigger.
"I saw one 20 to 25 feet (6 to 8 meters) across, and the hogs had knocked down a couple acres of corn right around that hole," he said.
Hogs did so much damage to a neighbor's 30-acre (12-hectare) hay field that the neighbor offered it free for Williams' use. He took the offer and installed an electric fence -- but fencing all his fields isn't practical.
Hogs also can spread dozens of diseases. Their rooting and wallowing can destroy pretty much any terrain, fouling waterways and exposing banks to erosion. Invasive plants often take over uncultivated areas rooted up by hogs, VerCauteren noted.
And hogs will eat just about anything. They compete with deer and turkey for acorns and also eat fawns and eggs, not to mention quail and sea turtle eggs.
Forty-one states joined USDA's feral swine control program in 2014, after Congress appropriated $20 million a year. New York and Idaho since left it after going two years without any confirmed sightings of feral hogs, program manager Dale Nolte said. He said five other states -- Washington, Maryland, Minnesota, New Jersey and Wisconsin -- are believed free of feral swine, and are in a two-year evaluation period to be sure.
The program included $1.5 million a year for toxic-bait research.
The federal government has previously approved a feral hog bait that uses the blood-thinner warfarin, but no states have approved it so far, VerCauteren said.
VerCauteren, who works out of Fort Collins, Colorado, worked on the sodium nitrite bait with scientists at Texas Parks and Wildlife Department, Auburn University and in Australia and New Zealand.
If the field trials work well, the new bait might get federal approval in 2020, opening the way for states to approve it. But at least for the first several years, landowners will have to get the USDA to set up the bait and feeders.
"It's not going to be on the shelves of Home Depot," VerCauteren said.
It won't replace trapping, helicopter hunts and other methods, but should be a powerful addition to the anti-hog arsenal, VerCauteren said.
Much of the work so far has involved finding a way to get pigs to eat sodium nitrite, which tastes nasty and breaks down quickly in the presence of air or water. Researchers had to microencapsulate the powder to hide the taste, and find a coating that would both stand up to chewing and keep the chemical stable from the time the bait is made until it hits a pig's gut. They worked up a hog-tasty formula for bait in which to mix it.
Researchers also had to make sure other animals couldn't get into the bait feeders, and that hogs killed by sodium nitrite were safe for scavengers.
They're working on making bear-proof boxes, using cameras and sound recognition so only pigs can get in, but that's probably a couple of years away, Vercauteren said.
"Right now we just won't use the bait where there are bears," he said.