Mud Snail Closures on Boulder Creek

Boulder Creek downstream of Valmont road is one of only two locations in Colorado where the non-native, invasive New Zealand mud snail has been found.

Mud snails can be spread by boots, waders, a dog's pads, and most anything they come in contact with. The snails are very tiny and thus can easily go undetected as they hitch a ride to a new area. Highly resilient, the snails can survive several days out of water and can withstand a wide range of temperatures.

Because they reproduce by cloning, it only takes one New Zealand mud snail to start a new colony!

Please stay out of the closure areas to avoid the spread of mud snails, and subsequent threats to our aquatic ecosystems.

OVERVIEW of entire closure area 2.33 Mb
Close up, Western closure area 2.39 Mb

Close up, Eastern closure area 2.33 Mb

Photo - New Zealand mud snails with a penny for scale.

Concerned about the possible spread of the Due to the highly invasive New Zealand Mud Snail and the potential for detrimental impact on Boulder Creek, the City of Boulder has enacted an emergency closure of all access to a stretch of the creek and several Open Space & Mountain Parks properties adjacent to the creek. This closure remains in effect until management actions are taken (such as fencing) or until information suggests that the closures are no longer necessary.

New Zealand mud snails (Potamopyrgus antipodarum), which are native to the Southern Hemisphere, were found in Boulder Creek in November 2004. The discovery in Colorado of the miniscule snail that has invaded rivers and streams across the West raises concerns that the fast-spreading invertebrate could push out native species and compromise the long-term health of the region's aquatic ecosystems.

U.S. biologists first discovered the snails in Idaho's Snake River some 20 years ago. Aside from Colorado, they have spread into Montana, California, Arizona, Oregon, Utah and Wyoming, including Yellowstone National Park.

Photo - a host of fully grown New Zealand Mud Snails with a key for scale.

At only 2-to-5 millimeters in length, the mud snails are difficult to contain once they have invaded an aquatic ecosystem, and are so small they cannot be skimmed from waters. The snails can cling to birds and other wildlife, and are thought to be spread by human and domestic pet activities, including hiking and fishing. They can be spread by boots, waders, and “most anything they come in contact with”, said Heather Swanson, OSMP Wildlife Ecologist. Highly resilient, the snails can survive several days out of water and can withstand a wide range of temperatures. The tiny invertebrates can even pass unscathed through the digestive tracts of fish.

Because they are self-reproducing “live bearers” that give birth to well-developed clones, it only takes one New Zealand mud snail to start a new colony in a stream or river. Officials stressed that public awareness is crucial to stopping the spread of exotic species in Colorado's streams, rivers and lakes precisely because of the difficulty of removing them once they have arrived. The Board of Directors of the Boulder Flycasters has endorsed the actions of the city in the closure of Boulder Creek.

“We appreciate the cooperation of the public during this closure to ensure that humans do not further spread the snail beyond their current distribution”, said Swanson. “We are working with local and national experts to find the best steps to control or manage these snails and will reassess the need for the closure as this process progresses.”

Last Updated on Wednesday, 13 January 2010 14:29