Pigs are hardy animals and prolific breeders, and in addition to the domestic animals reared on farms, nearly four million wild pigs now roam the United States.
Today's feral hog population is a hybrid of domestic pigs and Eurasian wild boars brought to North America in the early 1900s for food and sport.
Tyler Campbell is a research biologist at the National Wildlife Research Center's field station in Kingsville, Texas.
He says feral pigs can harbor more than 30 diseases—including the pseudorabies virus and brucellosis bacteria—that could negatively impact the livestock industry.
(Related photo: testing pork for dangerous bacteria.)
Campbell and his colleagues tracked several populations of feral hogs to find out how much interaction takes place between wild and domestic herds.
The team discovered that wild pigs came within close proximity of domestic swine facilities or even their farm-raised cousins—in some cases going "nose-to-nose."
"This had never been demonstrated before," Campbell said. "But now we have documented that it happens quite a bit."
Sundberg of the National Pork Board says his group is funding research on ways to mitigate feral pig problems and is educating producers about the health risks feral swine can pose to commercial herds.
In addition to health concerns, feral pigs can cause thousands of U.S. dollars in property damage.
With their big bodies and broad snouts, the portly pests ruin lawns and golf courses while foraging.
"They'll go in overnight and turn over a person's whole lawn so all the grass is root side up," Bob Repenning said.
Repenning is the land manager of Six Mile Cypress Slough, a 2,200-acre (890-hectare) swamp preserve in Fort Myers, Florida.
In the preserve, the wetlands flood during part of the year, forcing resident feral pigs to find drier ground—often on homeowners' property.
A nearby housing development reportedly spent more than $60,000 (U.S.) on fencing to keep out the trespassers.
And Repenning says he had 448 of the porkers removed within the last year from the slough, although the efforts seem to have had little effect.
"They're still running all over the place," he said.
In Missouri last week state wildlife officials publicly urged the nearly 500,000 licensed deer hunters to kill feral pigs too.
Feral hogs are often found in the remote, rugged portions of the state's Ozarks mountain range, where thick brush and timber make it hard to locate and kill the animals.
Adding to the problem is the rising occurrence of people illegally releasing hogs around the state for recreational hunting, says Rex Martensen, field program supervisor for the Missouri Department of Conservation.
More than 10,000 pigs freely roam across public land, primarily in the southern half of the state, he says.
Even so, Martensen is hopeful something can be done about the problem.
"We're at a point where given the right conditions and given the right control methods, we might be able to reduce—if not nearly eliminate—the feral hogs in the state," he said.
"But we're sitting precariously in the balance of missing that window of opportunity if we don't do something pretty quick."
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