The Science Behind Worm Grunting

Worm grunters imitate the sounds made by worm-hungry moles digging through the earth

• Hannah Schardt
• Feb 01, 2009

AS RECENTLY AS the 1960s, hundreds of people in the southeastern United States earned a living through a curious practice known as “worm grunting”: driving a stake into the ground, then rubbing the stake with a long piece of steel in order to produce a sound that, for reasons unknown, would drive hundreds of earthworms to the surface where they could be collected for bait. Now biologist Ken Catania of Vanderbilt University has found an explanation for the technique’s efficacy.

Without realizing it, worm grunters were imitating the sounds made by worm-hungry moles digging through the earth. By observing both earthworms’ reactions to grunting and their response to the presence of eastern American moles, Catania found that the invertebrates rapidly pop to the surface when they detect the presence of a mole—or a grunter. For more on earthworms’ role in the environment and the economy, see the article “Nature’s Gardener or Forest Invader?” in this issue.