Non-native New Zealand mudsnails have led to the closure of a trail in Boulder’s Open Space and Mountain Park system because they pose a serious ecological threat, the city of Boulder said in a news release today.
The city’s Mallory and Harmon cave area also is being closed because of white-nosed syndrome, which has led to a massive die-off of bats in the eastern United States.
“Both of these problems could seriously degrade our local ecosystems and threaten rare species of wildlife,” Eric Stone, resource systems director for Boulder Open Space, said in the release. “These actions are necessary to safeguard the natural resources on Open Space and Mountain parks lands.”
Stone said New Zealand mudsnails have been discovered on the Open Space property and, as a result, will lead to the closure of Dry Creek Trail and Trailhead, 6802 Baseline Road, which runs along Dry Creek near Baseline Lake.
According to Stone, the non-native New Zealand snails can reach very high densities in infested areas, competing with native mollusks and insects, and changing the aquatic ecosystem.
“Our biggest concern with Dry Creek is that it could be a source to spread snails to more pristine stream reaches both on and off” the open space lands, said Stone.
The snails attach themselves to shoes, felt-bottom waders or paws of animals and can survive for extended periods of time out of water. Their small size and high density, plus asexual reproduction — it only takes one snail to reproduce — makes preventing their spread the best method to control their species, according to officials.
Eric Fairlee, a pest management specialist for Boulder Open Space, said that the New Zealand mudsnails were discovered this week as he was preparing for a trail restoration project.
He said mudsnails were first discovered in the late 1980s in the Snake River in Idaho and have spread rapidly across the west. He said one New Zealand mudsnail can produce 40 million mudsnail eggs in a year. He said that in places like Yellowstone National Park, the New Zealand mudsnail has become the predominant invertebrate in Yellowstone streams, eating the bulk of the algae in the streams.
The Mallory and Harmon caves will be closed due to the white-nosed syndrome, a fungal disease that has killed bat populations in the eastern United States. The disease is suspected of killing bats in Arizona and the U.S. Forest Service has closed caves in western states, including Colorado, to protect the bat population.
Boulder said it was following suit in order to protect a colony of Townsend’s Big-eared bats living in the caves.
Heather Swanson, a wildlife ecologist for Boulder Open Space, said that the Townsend Big-eared bats are rare in the region. She said that closure is designed to protect the female bats and their nursing young that live in the Mallory cave and the male Townsend bats that live in the Harmon cave.
Swanson said that the bats are a “really critical link in the ecosystem” because they eat insect pests like mosquitoes.
It is believed that people who use the caves help spread the fungal disease.
The closures will remain in effect until the threats to the ecosystem have been mitigated.
Howard Pankratz: 303-954-1939 or hpankratz@denverpost.com.
