English: Gary and Audrey Revell demonstrate worm grunting to collect bait in the Apalachicola National Forest in Florida's panhandle. The Revells are professional bait collectors and make their living by collecting the large earthworms native to the area. These worms (Diplocardia mississippiensis) respond to vibrations by rapidly exiting their underground burrows. The vibrations are created by first pounding a wooden stake (called a “stob”) into the ground, and then rubbing the top of the stake with a flat piece of metal (a “rooping iron”). This is repeated in different areas until thousands of worms have been collected. doi:10.1371/journal.pone.0003472.s003