U.S. goes after sly, pesky feral pigs

[byeya]

2. Many of these animals are descended from European wild boars brought to the USA by hunters

and let loose for sporting activities. In the Great Smoky Mtns Natl Park they are an ongoing problem. The park gets rid of them, usually by shooting, and they repopulate by coming in from other lands.
Other wild swine are descended from the razorback hogs grown by farmers years ago. It was a common practice to let them roam free and fatten up on acorns and chestnuts and other native plants and then gather them up come "hog killin' time"
Some were never recaptured. They are very destructive of native plants particularly native lilies and other plants that grow from bulbs or bulb-like structures.