Lesser Known Invasive Species Causing Problems in the United States


Invasive species crawl, wiggle, jump, fly and swim in almost every corner of the country. Some invasive species are well known (like feral hogs, murder hornets, emerald ash borer, etc.), but others slip more easily under the radar. Still, species that don’t spend much time in the spotlight can be just as frustrating to deal with as their more high-profile counterparts. Here are three lesser-known invasive species that are becoming a problem.

Asian jumping worm

Susan Day, UW Madison Arboretum

Crazy worms, snake worms or Alabama jumpers – these pesky invasive worms take root in pockets all over the Midwest and Northeast.

Jumping worms look different from the common earthworms you might recognize in your garden. That’s exactly what jumping worms do – they jump and thrash around in a distinct way. Another feature that sets them apart is the white collar (or clitellum) on a jumping worm. It is smooth, milky white, and located about one-third the length of the worm’s body from its head.

These wavy worms actually pose a significant threat to forest habitats. They deteriorate the quality of the soil, which makes it difficult for plants to root. This in turn leads to a reduced food source for native creatures such as white-tailed deer, rabbits and others. Jumping worms devour the top organic rich layer of nutrient dense matter near the surface of the soil and leave behind a gritty soil full of worm castings that is stripped of all nutritional value. According to Tim McCay, a biology professor at Colgate University, this changes the physical structure of soil, turning it into something that looks like coffee grounds or boiled hamburger meat.

McCay has been involved in identifying invasive worms in New York State for the past three years.

Jumping worms are asexual or parthenogenetic, meaning they can produce eggs without needing a mate. This means that even a capricious worm can create a new population. They also mature in just 60 days. So it doesn’t take long for a cluster to be established in one place. The first hatch usually occurs from late June to early July. In September, a population can double. The adult jumping worms perish during the winter, but the larvae survive in microscopic cocoons in the soil or leaf litter. These larvae hatch in late spring and the cycle begins again. A map of registered jumping worm establishments in the United States is available from iMapInvasives.

African clawed frog

lesser known invasive species

A small frog with a large belly and black claws on its legs, the African clawed frog is an invasive amphibian that disrupts ecosystems and affects native populations, including trout and salmon.

African clawed frogs have voracious appetites and eat large amounts of native insects, fry and tadpoles, according to Max Lambert, a researcher with the Washington Department of Fish and Wildlife. When African clawed frogs enter an aquatic system, they can quickly decimate native populations. Established infestations of these gluttonous frogs have been reported in many states, with concentrations in Washington, California, and Florida.

They carry many diseases and with that the potential to introduce harmful pathogens into native ecosystems that can destroy native populations of amphibians and fish. They are such a well-known vector of disease that if African clawed frogs are discovered in a body of water, then said water must be quarantined due to the diseases they carry. Even people should be careful when handling African clawed frogs. These same diseases can be transmitted to humans and cause disease. People should wash their hands thoroughly after any contact with African clawed frogs.

African clawed frogs are generally easy to distinguish from most native frogs. They have patchy olive to brown skin coloration with no eyelids, tongues, or vocal sacs. The front feet are not webbed, but the back feet are fully webbed and have sharp, inky claws. Their tadpoles look like small catfish, with long barbs extending to either side of the chin.

chinese mitten crab

lesser known invasive species

A fast-walking crab with two large hairy claws – this is the mitten crab.

Easily identified by the unmistakable fur that covers their front claws, other features include a notch between the eyes with four spines on either side of the notch and eight sharp, pointed legs.

In China, where mitten crabs originated, they are considered a delicacy in many dishes. In the United States, they are banned, but this does not prevent the sale and transport on the black market of these distinctive creatures.

Mitten crabs are ferocious eaters that prey on local wildlife, such as native fish populations. This not only threatens these fish populations, but also game that consumes fish, such as waterfowl. They are a huge annoyance to fishing. These crabs have become such a detrimental invasive species that they’ve landed a spot on the list of the world’s top 100 invasive species.

According to the Smithsonian Environmental Research Center, these problematic crabs have already spread to several California waterways, the Connecticut coast, the Chesapeake and Delaware bays, and the Hudson River. They can migrate over land or water up to 11 miles per day.

These three invasive species have already reared their ugly heads and negatively impacted their non-native environments. Which species will be the next to worry about? Only time will tell.

READ MORE: Invasive Chinese crabs are quietly taking over New England

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