Self-cloning New Zealand mudsnails have been detected in Carter Lake, Colorado, for the first time, prompting wildlife officials to expand boat inspection checkpoints. Colorado Parks and Wildlife warns that the invasive, quarter-inch mollusks can rapidly multiply into thousands from a single individual, disrupting aquatic ecosystems while posing no risk to human health.
New Zealand Mudsnails Confirmed in Carter Lake for the First Time
Colorado water managers are facing a new ecological challenge in Larimer County. Colorado Parks and Wildlife confirmed that New Zealand mudsnails have established a presence in Carter Lake, a popular reservoir southwest of Loveland, according to CBS News Colorado, marking the first time the species has been found in the popular reservoir.
This marks the first known detection of the invasive species in the waterway, adding a prominent new location to a statewide list that already spans 41 other bodies of water, according to regional reporting. Officials are not promising to remove them because, once established in a large waterway, eradication is considered extremely difficult. Instead, the focus has shifted to containment, and that effort depends heavily on the people who use Colorado’s lakes and rivers. The discovery at Carter Lake is the latest example of the species turning up in Colorado.
The snail in question is barely the size of a nail clipping, brown and easy to miss in lake sediment. A person could carry it away on wet gear without ever realizing it was there. New Zealand mudsnails grow to about one quarter of an inch, making them easy to overlook as they cling to wet vegetation, fishing equipment, or muddy surfaces. That diminutive size is part of what makes them effective hitchhikers, as recreational visitors can easily carry them away on damp gear without realizing it, the outlet reported.
How Self-Cloning Biology Drives Rapid Infestations
The primary threat stems from an unusual reproductive strategy, and Colorado Parks and Wildlife says a single New Zealand mudsnail can quickly become thousands. In the western United States, the mudsnails are all female, and each one is born carrying embryos, as recorded by the National Park Service. They reproduce asexually, meaning a single snail can create an entire population without needing a mate.
That ability makes them especially difficult to control. The animals are nearly invisible, self-sufficient breeders, and in other parts of the American West they have reached densities that can alter the balance of aquatic ecosystems. Officials note that populations can reach densities of hundreds of thousands of snails per square meter. Their dense numbers can also clog reservoir inlets, outlets, and recreational structures.
CPW spokesperson Kara Van Hoose described the ecological challenge mudsnails create in simple terms. These mud snails are very big eaters, and they just kind of go through all of the different nutrients that are in an ecosystem and don't really provide any benefits back to anything else in there,
Van Hoose said.
According to Colorado Parks and Wildlife, the snails compete with native aquatic species for food, including the resources needed by mayflies and other invertebrates. That disruption can affect the larger food chain, including fish and birds that rely on those organisms. Furthermore, they offer little nutritional value to the broader food web. Their lack of natural predators worsens the problem. Van Hoose said fish do not benefit from eating the snails, and birds that consume them may pass them through digestion “unscathed.” Their shells allow them to survive, meaning they take energy from the ecosystem without becoming a meaningful food source. CPW has emphasized that the snails do not threaten human health. The concern is the damage they can cause to aquatic environments.
Containment Replaces Eradication as Colorado Focuses on Prevention
Once mudsnails settle into a large body of water, removing them becomes an enormous challenge. Van Hoose explained that eliminating them would take extreme measures. It would take Herculean efforts to remove them from a waterway, like draining the water, years' worth of treatment, and all of that,
she said. Eradication in a large water body is considered nearly impossible once the species takes hold, officials confirmed.
Because of those challenges, CPW expects the snails will likely remain in Carter Lake because of how easily they reproduce, so the agency’s focus now is to prevent them from being transported elsewhere. The realistic goal is preventing them from moving into nearby waterways rather than attempting a full removal effort. Authorities have expanded boat inspection checkpoints at Carter Lake to look for mudsnails in addition to other invasive species, such as zebra mussels, inspecting vessels upon both arrival and departure, according to the reporting, but say inspections alone cannot stop every transfer.
The Clean, Drain, and Dry Mandate for Waterway Visitors
Mudsnails can survive outside the water for days and remain on damp equipment for weeks. That means a single trip with wet gear can create an opportunity for the species to spread. So it's best just to kind of contain the spread and then prevent it from spreading further,
Van Hoose added. Because the snails can survive for days out of water and for weeks on damp gear, officials emphasize that checkpoints alone cannot catch every transfer. The burden rests heavily on recreational users.
CPW’s Pain in the ANS
outreach campaign has a simple message for anyone enjoying Colorado’s waterways: clean, drain and dry. Visitors to Carter Lake and other affected areas are encouraged to thoroughly clean equipment before moving between lakes and rivers. Under the state’s initiative, visitors using boats, kayaks, paddleboards, fishing equipment, inner tubes and anything else that comes into contact with the water are urged to thoroughly clean, drain, and dry all equipment before transporting it to a new body of water, the coverage noted. The process matters because even a small amount of moisture can harbor the invasive species.