The top end of the stake was then rubbed with a long (100×7 cm) flat metal object with a smooth surface ( figure 1 a supplementary video in the electronic supplementary material).
Grunting was performed by first hammering a wooden stake into the soil to a depth of approximately 30 cm. Grunting vibrations were generated by one of the authors (M.A.C.), who had previously used this technique to survey earthworms ( Hendrix et al. For this reason, burned areas are attractive to bait harvesters, and are preferentially used shortly after prescribed fires have been conducted ( Hendrix et al. Both sites had recently undergone prescribed burning and had very little emergent vegetation or detritus obscuring the ground surface, making it easier to find worms. The hypotheses explaining the adaptive significance of earthworms surfacing in response to vibrations are discussed.Įxperiments were conducted in the pine ( Pinus palustris and Pinus elliottii)-dominated forests of Apalachicola National Forest, Liberty County, Florida (compartments 100 and 110) between 08.00 and 10.00, 14–15 April 2008. We record the vibrations being transmitted through the soil using a typical worm grunting technique, and test the hypothesis that earthworms surface in response to a vibration stimulus. Vibrations have not been recorded, and the relationship between vibrations and worm emergence has not been documented. Similar practices are used to collect earthworms elsewhere, including England, where worms are ‘charmed’ out of the ground by ‘twanging’ the handle of a garden fork, the tongs of which are inserted into the soil ( Edwards & Bohlen 1996).ĭespite their prevalence, worm grunting and similar techniques have not been examined experimentally. (1994) reported significant reductions in earthworm biomass due to bait harvest in Florida, while noting that during some seasons thousands of earthworms per hectare per day can be harvested via grunting. Appreciable income can be generated by collecting worms, but this can result in negative effects on earthworm populations and their associated benefits to plant nutrition ( Hendrix et al. Worm grunting is economically and ecologically important in localized regions. A wooden stake is driven into the ground and typically scraped with a long metal object until worms come to the soil surface.
In the southeastern USA, worm ‘grunting’ is commonly practiced to collect earthworms for fish bait.
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