Under a lowering sky, a brown creek meanders through soaking grass. Bill Dunson is hunting snapping turtles. He stands on the creek bank and adjusts his earphones, raises an aluminum antenna—a cross with three horizontal bars—and turns it from side to side.

Mosquitoes by the dozens ride the shoulders and back of Dunson's coveralls; they lift from his neck, flying heavily. Dunson twirls a dial on the receiver, which he carries at his waist in a blue nylon bag.