April 26, 2017

Charming Earthworms for Science

Laura Genello

Laura Genello

Guest Blogger

Johns Hopkins Center for a Livable Future

This post is the fourth in a series – Letters from the Low Country – about food and agriculture in the Netherlands, written by Laura Genello as she studies organic agriculture at Wageningen University.

Almost everyone agrees that earthworms are good for soil in built environments, and for more than a century, we’ve been researching their role in forming soil. In fact, fascination with earthworms can be traced back to Charles Darwin, who first documented their soil forming behaviors. My own interest in worms and soil brought me to a quirky competition held by Wageningen University in the Netherlands.

The worm charming winners, team Rooted Dune, show off their trophy.

On a sunny Thursday in April, a group of over 50 soil enthusiasts and worm lovers came together in an apple orchard on the Wageningen campus in support of these fascinating creatures. The gathering was the first annual Wageningen Worm Charming Championship, sponsored by the university’s soil biology chair group. Worm charming is the practice of luring worms from the soil using only vibrations and is often used by fisherman to catch bait. While it may not be the most popular sport, competitive worm charming competitions exist throughout the world. In addition to competing for bragging rights, the 11 teams of worm charmers were luring worms from the soil for science. More on that in a minute, but first, the basics of worm charming:

Competitors use a cymbal and a pitch fork.

The competition had simple rules. Each team was assigned a 3×3 meter plot, and had half an hour to coax worms from the darkness of the soil into the bright sun of a spring afternoon using only unamplified vibrations. The team with the most worms at the end of half an hour wins. Most teams used at least one pitch fork, stuck in the ground and vibrated by the handle, but there were a diversity of other methods as well, including dancing in scuba flippers, beating the ground with badminton rackets, and using musical instruments like flutes or cymbals. At least one team heeded the event flier and showed up in costume, because, as the flier stated, “fancy dress may exert additional mystic powers over the worms.” (That last statement has not been scientifically verified).

Jan Willem van Groenigen, professor at the soil biology group, told me that no one knows for certain why vibrations send worms towards the surface, but there are two theories. The first is that the vibrations mimic the sounds of a digging predator, such as a mole, and that the worms head to the surface for safety. The other is that the vibrations imitate the sound of raindrops. In fact, some species of birds have learned to exploit this worm behavior, and will stomp on the ground, seeking an easy meal.

The soil biology department decided to hold a worm charming competition as an educational event to raise awareness of the importance of soil biology. But the event also has a very practical function for the researchers. In order to study and learn more about earthworms, the researchers at Wageningen need study subjects. According to Jan Willem there are around 25 different species of earthworms in the Netherlands alone, and most of them cannot be easily ordered from a supplier. (It’s worth noting here that the red compost worms that many people buy for home compost bins are surface dwelling worms that live in leaf litter. They are a different type of earthworm than those that burrow through the soil.) All of the worms collected in the worm charming competition will be introduced to Wageningen’s new “worm hotel” where the researchers will store them, allow them to breed, and have easy access to a diversity of species when they need to conduct research. The worm hotel is a series of small plots that are enclosed on four sides by an underground wall. Each plot will be maintained at the optimal conditions for the species of worms present to ensure they have sufficient moisture, and the right soil texture. Jan Willem tells me that the hope is that the worm hotel will make it easier for researchers to do their work by ensuring easily accessible populations of a diversity of species.

Laura Martinez Garcia uses a pitchfork to charm worms.

Over celebratory drinks and cups of “worms and dirt” (chocolate pudding, Oreo crumbs and gummy worms), the winners are announced. The competitors raised 716 worms from the soil, with the per team numbers ranging from 34 to 122. Ironically, the winners were a group of plant ecologists with no worm charming experience, putting the soil biologists to shame. I was impressed by how effective and quick worm charming had proved to be. However, the ever-skeptical scientists at the soil biology group quickly reminded the crowd that under each plot there were probably 2,000 individual earthworms, so we shouldn’t be too proud. In fact, the current world record for worm charming is held by Sophie Smith of the UK, who, at the age of 10, charmed 567 worms from the soil in a half an hour.

Overall, despite the relatively low worm numbers, spirits were high and the event was a success. Jan Willem tells me that next year they hope to expand the audience and bring in secondary schools to use the event for educational purposes. In the meantime, the new residents of the worm hotel will help in improving scientific understanding of earthworms in the environment.

Images: Laura Genello 2017.

One Comment

  1. First of all, I’m quite fascinated with the worm charming sport. I didn’t thought that there’s a name for catching worms from the ground. I didn’t know that worms are attracted to vibrations. I think this is a good topic for a research. Good work !

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