How to Poison Feral Hogs (and Only Feral Hogs)

Early one winter morning in 2020, Kurt VerCauteren discovered a cluster of dead birds in a barren field in northwest Texas. They were small birds, mostly dark-eyed juncos, but also a smattering of white-crowned sparrows.

VerCauteren’s team had poisoned them, inadvertently. The clues were clear, the death uncomplicated: The birds had flown in before dawn to scavenge deadly morsels of a contaminated peanut paste, left behind after a sounder of wild hogs had torn through the area in a feeding frenzy. The birds likely died within minutes of eating.

“I couldn’t even see the crumbs,” says VerCauteren, a wildlife biologist at the U.S. Department of Agriculture in Fort Collins, Colorado, who has spent years developing and testing pig poisons. The birds were the unintended victims of a field experiment to test a toxicant—one intended for feral pigs, but no other animals—that had been developed in Australia. In the days before, VerCauteren and his collaborators had assembled heavy, sophisticated feeders and filled them with the mash laced with a heavy dose of sodium nitrite, a salt often used in processed meats. When the pigs ate, they’d left tainted crumbs behind—not many, but enough.

“It takes a handful to kill a hog,” VerCauteren says. But, he adds, it only takes an amount the size of “a grain of rice to kill a little bird.”

There are currently no poisons that can be legally used in the United States against wild hogs, but not for a lack of options. For nearly a century, scientists have investigated chemicals that can fell big, vertebrate pests—particularly feral swine. The animals have become a across the country, with as many as of them causing enormous damage to crops, livestock, and native habitats from North Carolina to California and Texas to Florida. “When you have a grossly overabundant species, the kind of