In his preliminary research Catania found some other interesting clues. One was the observation by the famous Dutch ethologist Nikolaas Tinbergen that one species of gull performs a "foot paddling behavior" that appears to bring up earthworms to the surface, a response he attributed to an innate reaction that enables the worms "to escape their arch enemy the mole." More recently the American naturalist John Kaufmann who studied wood turtles reported that they engage in a stomping behavior that brings earthworms to the surface so they can eat them.
Catania's first step was to determine whether moles live in the areas where the worm grunters practice their trade. He found that eastern American moles (Scalopus aquaticus Linnaeus) were plentiful. The Revells took him to the best places in the forest, where he found more than 200 mole tunnels in the vicinity of 94 holes left by worm grunters.
Once that fact was established, they examined the practice of worm-grunting. Apalachicola is the home for a native species of earthworm Diplocardia mississippiensis that are prized for bait because of their large size. One of Catania's first experiments was to measure the worms' response to worm grunting. He used geophones to record the sub-surface vibrations that the method created.
Catania discovered that a single worm grunting session forced hundreds of earthworms to the surface within 12 meters (13 yards) of the stake. "This makes it possible for an experienced worm grunter to collect thousands of worms in a day," Catania says.
In one case, instead of collecting the worms, the biologist observed their behavior after they surfaced. After traveling a significant distance on the surface they began searching for a plac
|Contact: David F. Salisbury|