COLUMBIA, SOUTH CAROLINAA layer of frost clings to the grass on the morning Tony DeNicola sets out to check his trap. It’s late January in South Carolina. The sun is rising, the fog is lifting, and the frogs are croaking from somewhere in the dark loblolly pines. In a whisper, DeNicola explains what will happen.

“I wait for them to tire themselves out and then start tipping them over,” he says, shifting a loaded rifle from his shoulder and cautiously approaching a clearing in the forest beside a small cattle ranch.

Over centuries, this adaptable, omnivorous creature has rooted its way from Florida to Kansas, inundated Texas and California, and recently has been banging for entry at the northern border of Montana. Today, there