Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

These invasive worms jump when handled. © DNR File

The name speaks for itself. These invasive worms jump when handled.
© DNR File

June 2015

Jumping worms

There's a new creepy–crawly in Wisconsin.

Bernadette Williams and Colleen Robinson Klug

In October of 2013, the Wisconsin Department of Natural Resources discovered a population of jumping worms in Dane County — the first to be identified and reported in the state. Jumping worms belong to the genus Amynthas and are also known as "crazy worms" or "Alabama jumpers."

These worms are a big deal, but to understand them best, we'll start with a refresher on earthworms in general.

Earthworms in Wisconsin

We don't have any native worms in Wisconsin. Our native worms were destroyed during the last ice age. That means Wisconsin forests as we know them evolved without earthworms. It's hard to believe worms are actually an invasive species. Not many people suspect that "nature's recyclers" have a dark side, but they do.

Historically, the verdict on worms has been in flux. Before Charles Darwin published one of his most popular works, "The Formation of Vegetable Mould through the Action of Worms, with Observations on their Habits" in 1881, worms were viewed as a pest and nuisance. Darwin's research changed public perception of these remarkable animals, which perhaps has played a role in their inevitable spread.

In Wisconsin, we've documented over 20 European species of earthworms in a variety of ecosystems. Researchers have studied their negative impacts on forest regeneration, ground nesting bird populations, and their role in facilitating the spread of terrestrial invasive plants like garlic mustard and buckthorn.

Problems caused by earthworms

Forest floor leaf litter is comparable to the skin on an animal. It retains moisture, protects roots, breathes, prevents erosion, deters pathogens and non-native plants and promotes seed germination. When leaf litter is consumed by earthworms it's like removing the skin of the forest floor. Disturbance from earthworms exposes the soil and causes erosion, compaction and increased rainwater runoff. This disturbance favors invasive plants, beginning a cycle of non–native invasions competing for critical resources. The result is less diversity of native plants and animals in our forests.

Before October 2013, we knew earthworms were invasive. What we didn't know was that we had a new worm in the mix in Wisconsin.

Problems caused by jumping worms

All earthworms are invasive and they can cause a lot of problems in places they don't belong, like Wisconsin's northern forests. Jumping worms are a concern because they can consume the litter layer faster than any other earthworm in the state. Where jumping worms are present, fallen leaves and topsoil are processed by the worms until the soil becomes granular, dry and looks similar to coffee grounds. We have even observed a decline in European earthworms where jumping worm populations are established. Research is ongoing to better understand why this happens.

We don't know the full effects jumping worms may have on our native forests, but given what we know about European species it's not something we want to find out. What we do know is that in Wisconsin, jumping worms appear to be concentrated in urban areas, though they may be hitching a ride to new areas by multiple means.

The scoop on jumping worms in Wisconsin

In 2009, all 51 species in the genus Amynthas were listed in Wisconsin's first "Invasive Species Rule," (Wis. Admin. Code Ch. NR 40). They were classified as a "Prohibited Species" because we knew enough about their "dark side" to know we didn't want them in the state. This law helps prevent the introduction of unwanted species by making it illegal to sell, introduce, transport, possess and propagate them in the state.

Unfortunately, some species make it here anyway.

Jumping worms are native to Southeast Asia.

The worms or cocoons may have been accidentally introduced in a potted plant, nursery stock or soil.

Concerned about the discovery in October 2013, the Department of Natural Resources launched an outreach effort to inform people about jumping worms. The public became actively involved in reporting their presence. During the summer and fall of 2014, DNR staff verified a number of populations in five counties. This surveillance allowed us to gain a better understanding of their spread and the possible ways they are moved from place to place. It also required the department to reassess Amynthas' "Prohibited" classification under NR 40.

With populations established in five counties, jumping worms no longer fit the definition of "Prohibited." It was recommended they be reclassified as a "Restricted Species" to better limit their unintentional spread. This classification still prohibits the sale, introduction, transport and propagation of jumping worms in the state.

Jumping worm basics

This is no ordinary worm. Jumping worms didn't get their common name on a whim. They earned it. Their appearance, life cycle, biology and behavior are nothing short of extraordinary, and once you see them you'll understand why this unusual worm is commonly called the "crazy" or "jumping" worm. When they are disturbed, jumping worms thrash violently, slither like snakes and even jump into the air.

Jumping worms are darker and smoother than other earthworms in Wisconsin. They are relatively easy to identify if you take a look at their clitellum (the band around the body of a worm). The clitellum on a jumping worm is milky white to gray-colored, smooth and completely encircles the body of the worm. In contrast, the clitellum of European earthworms does not wrap entirely around the worm. Also, on a European species it is raised above the body of the worm, not smooth.

What makes jumping worms truly unique is their life cycle. While we are still learning the full life cycle and biology details, we already know jumping worms are asexual, which means an individual can reproduce solely on its own. These worms reach maturity within 60 days of hatching. Then they reproduce and drop cocoons in the soil. The cocoons hatch and start the cycle all over again. The adults do not survive Wisconsin winters, so the life of an individual worm ends there.

The bad news is that the cocoons those adults have dropped into the soil do survive Wisconsin winters. It's this ability that allows the next generation of jumping worms to go undetected well into the spring growing season, as tiny cocoons rather than adult worms.

You have surely seen a variety of European earthworms when you start turning your soil, putting in your vegetables or annuals and splitting your perennials in spring. These European worms have overwintered and become active and visible in spring. Be assured, you will not find jumping worms during that time of year. Surveys in Wisconsin during the summer of 2014 showed adult jumping worms did not become apparent until late June and early July.

The temperature requirements needed for cocoons to hatch is something we don't fully understand, but we know that jumping worm cocoons hatch earlier than those of European worm species. With this early hatch, jumping worms reach maturity by early summer which allows for a second hatch of cocoons that can lead to infestation levels of jumping worms by early fall.

What are we doing about it?

In January 2015 the Department of Natural Resources organized a committee of representatives from the green industry, composters, master gardeners, cities and municipalities and the University of Wisconsin-Extension to develop Best Management Practices to minimize the spread of jumping worms and educate the public.

Research to further understand jumping worms will take time, but that doesn't mean we have to wait to spread the word and reduce the spread of these worms.

As with all invasive species the goal is to minimize their spread. That can be as simple as following these suggested BMPs:

  • Arrive clean, leave clean. Clean soil and debris from vehicles, equipment,gardening tools and personal gear before moving to and from a work or recreational area.
  • Watch for jumping worms and signs of their presence. If you find them, report them to the DNR by email at invasive.species@wi.gov.
  • Educate yourself and others to recognize jumping worms.
  • Only use, sell, plant, purchase or trade landscape and gardening materials and plants that appear to be free of jumping worms.
  • Only sell, purchase or trade compost that was heated to appropriate temperatures and duration following protocols for reduction in pathogens (see Wis. Admin. Code Ch. NR 502.12).

The keys to dealing with any invasive species are: prevention, control, monitoring, disposal and education.

While we still have unanswered questions, you can be a part of finding the answers. The First Detectors Network will help us document jumping worms across the state this summer and you can join at: University of Wisconsin–Extension First Detector Network. You can also report findings directly to the Department of Natural Resources by email at invasive.species@wi.gov, or go to dnr.wi.gov and search "earthworms."

Bernadette Williams is a conservation biologist.

Colleen Robinson Klug is a natural resources educator in the DNR Forest Health Program.