A species of snail smaller than a dime is quietly spreading across north-central Montana — and for the farmers, ranchers, and community members in its path, the damage it can cause is anything but small.
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The Eastern Heath Snail — a non-native invasive species originally detected in Belt, Montana — has now spread to Cascade, Chouteau, Judith Basin, and Fergus Counties, according to the Central and Eastern Montana Invasive Species Team.
For Belt resident and artist Ron Carlson, the first signs were easy to miss.
"We started noticing a few of them. We didn't know what they were," Carlson said.
The white shells initially appeared almost like gravel or rocks scattered on the ground. But when the numbers started growing, Carlson knew something was wrong.
"People come down here and study the snails. About two months out of the year, every year. They've been doing that to try to figure out how to take care of 'em or get rid of 'em," he said.
So far, no reliable solution exists to eliminate the Eastern Heath Snail once it is established in an area. The species is white with brown spiral bands, measures between 16 and 22 millimeters in diameter — slightly smaller than a dime — and is known for its massing behavior, clustering in large numbers on fence posts, vegetation, and other upright objects to escape ground heat.
Brent Smith, Program Manager for the Central and Eastern Montana Invasive Species Team, says the agricultural impact is real — and it starts with the machinery.
"When you start smashing up large quantities of them and then let them dry, they pretty much turn into a little super glue for you. So, it gums up machinery and can foul your equipment," Smith said.
Beyond machinery damage, Eastern Heath Snails degrade canola, grain, and pulse crops, contaminate hay bales, and can act as vectors for plant and animal diseases.
The snails are spreading primarily because of human activity — moving on vehicles, equipment, hay bales, and infested soil. Smith says the most important thing residents and farmers can do right now is stop moving them — and start reporting them.
"We're just asking people to keep an eye out and quit moving them around because they're moving because of us. Go ahead and do a quick report on iNaturalist, and that allows us to get a nice location, a photo, and to be able to try to confirm, you know, if that is in fact an eastern heath snail," Smith said.
What to look for:
- White or beige shell with dark brown spiral bands
- Slightly smaller than a dime — 16 to 22 millimeters in diameter
- Often found massing on fence posts, propane tanks, vegetation, and other upright objects during hot weather
How to prevent the spread:
- Check and remove snails from vehicles and equipment before moving between locations
- Do not move dirt, gravel, or hay that may be infested
- Mow vegetation to five inches or less
- Remove trash and debris that provide hiding places
How to report a sighting:
- Report on the iNaturalist app — include a photo and location
- Contact the Montana Department of Agriculture at (406) 444-9066
- Contact your local MSU Extension Office
