Kyle Peveto
In every parish of Louisiana, groups of feral pigs roam the countryside.
The packs of pigs, called sounders, are extraordinarily destructive. They devour crops, dig up trees and eat food that other animals depend upon for survival.
“They’re omnivores,” said Dr. Jim LaCour, state wildlife veterinarian with the Louisiana Department of Wildlife and Fisheries. “They’ll eat anything with a calorie.”
The Louisiana Department of Wildlife and Fisheries estimates the state’s population of feral pigs at more than 900,000. There could be as many as 9 million in the United States, according to the U.S. Department of Agriculture.
Hunters can shoot feral pigs all year. Landowners and agricultural producers build traps and pens to catch them. Yet the pigs’ numbers continue to grow.
A lethal pig bait designed by LSU AgCenter researchers and LSU chemists could be one answer to the proliferation of feral pigs. Over the past eight years, Glen Gentry, a reproductive physiologist with the AgCenter, has led the research and development of the baits, which are small rubbery balls packed with sodium nitrite, a compound often used as a food additive that is lethal to pigs in the correct dosage.
“It will be a valuable tool once everything gets straight and perfected,” LaCour said.
History of Feral Pigs
Feral pigs have not always been a destructive force in Louisiana. An expedition led by Spanish explorer Hernando de Soto introduced pigs to the Americas in 1539, according to the U.S Department of Agriculture.
On the frontier for centuries after, settlers often allowed their pigs to roam freely and fatten up on acorns and other nutrition available in the forests and grasslands before rounding them up and slaughtering them. These pigs reproduced, and their populations grew.
For years, wild pigs lived in isolated regions of Louisiana, LaCour said. They thrived around Catahoula Lake in central Louisiana and in the Pearl River basin in the southeast. Then, in the 1980s and ’90s, hunters transported wild pigs to other regions of the state to have more areas to hunt them, LaCour said.
“They are our most reproductively efficient large animal, basically,” LaCour said. “They bred and their populations grew exponentially, and they have kind of taken over the landscape. They’re in all 64 parishes.”
They also carry several diseases, including swine brucellosis, which can be transmitted to humans. Packs of pigs eat turkey eggs and dig up seedlings, which hurts forests. In rare cases they have used their tusks to kill cattle, LaCour said.
Feral pigs root and dig wherever they go, causing erosion and damage to crops. Shaun Tanger, a former AgCenter economist, estimated in 2016 that feral hogs caused at least $74 million in damage to Louisiana farms.
“There's a smorgasbord of stuff that the pigs can eat in Louisiana,” said Gentry, who is the director of the AgCenter Central Research Station in Baton Rouge and coordinator of the Bob R. Jones-Idlewild Research Station in Clinton, where much of the feral swine research takes place.
LaCour and Gentry often compare feral pigs to rats and label the swine problem an infestation. Sows can have two litters of piglets a year, and they average six piglets per litter, LaCour said. According to studies of feral pig management, to maintain a steady number of feral pigs, 70% to 75% of the population must be killed annually.
Louisiana hunters regularly kill 200,000 to 250,000 a year, LDFW surveys find. Hunting alone cannot control the population, LaCour said.
Developing the Bait
Nine years ago, as the feral pig problem grew, the AgCenter received grant money from the Pennington Family Foundation to study ways to control the population, and Gentry was chosen to lead the research. Additional funding came from the Louisiana Soybean and Grain Research and Promotion Board. While developing a method to control pigs, the team also bought traps, placed them on landowners’ properties and caught pigs for research.
Research led the team to sodium nitrite, a food additive used to cure meats. However, it can become lethal to animals in the right doses.
The feral hog team developed a bait made of menhaden fish that pigs would readily eat and found ways to pack the fish with sodium nitrite. Simultaneously, they worked on ways to deliver lethal bait only to pigs and not deer and other animals.
They developed a system using wildlife feeders that dispense corn and game cameras linked to cellphones. Landowners can receive photographic evidence that pigs are eating the corn from the feeders, then they can trigger the release of sodium nitrite baits to kill the pigs.
“They will consume our baits over the corn,” Gentry said. “They prefer the baits, so they eat the baits.”
At first the team struggled with ways to place the sodium nitrite in a capsule within the fish, Gentry said. Then Gentry reached out to the LSU Department of Chemistry for help. John Pojman, the chair of the department, put his lab’s scientists onto the problem. They found that sodium nitrite did not have to be encapsulated within the bait.
“The problem was that sodium nitrite will break down into different nitrogen oxide compounds and they have the smell kind of like a swimming pool, that chlorine smell, and they won’t eat it then,” Pojman said.
Pojman’s lab solved the problem by adding an ingredient similar to an antacid meant for indigestion, which kept the pH level low.
At Pojman’s lab, research associates have fine-tuned the bait formulation. Now it’s a rubbery, fishy ball designed not to crumble when pigs eat it, which should prevent other animals from consuming the crumbs.
Pojman is pleased his lab could help with the cooperative effort to humanely cut feral pig populations.
“That’s the advantage of being a big university like LSU,” Pojman said. “It’s fun. I enjoy working with the AgCenter because there are interesting projects.”
According to Gentry’s research, it takes two to three baits to kill a 300-pound hog in about two hours. The matriarch of the sounder typically eats the baits first because she runs the pack. Then more baits can be released to the rest of the group.
“As soon as the elder pigs are done, they walk off and everybody else comes up to the bowl,” said Ariel Bourgoyne, the research associate who studies the pigs’ reactions to the baits.
The Future
For the past few months, Bourgoyne has been testing different iterations of the baits Pojman’s lab has developed, running trials to see which bait pigs prefer and perfecting the delivery system.
Gentry and Pojman visualize a commercial future for the bait system once the research and development team is satisfied with its performance. That future will include seeking patents and getting federal and state approval for the process. Landowners who wish to use the lethal baits may one day need some form of pesticide applicator license.
Some hunters worry that the lethal baits could wipe out the feral pig population, Gentry said, but that is unlikely.
“We’ve been poisoning rats for 50 or 60 years, and we still have rats,” Gentry said. “When we do this to pigs, you’re still going to have pigs.”
Kyle Peveto is an assistant communications specialist in LSU AgCenter Communications and associate editor of Louisiana Agriculture.
(This article appears in the winter 2022 issue of Louisiana Agriculture.)
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