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Agriculture officials are investigating the discovery in Montana of a land-dwelling snail species not previously found in the western United States.

The USDA's Animal & Plant Health Inspection Service (APHIS) confirmed on August 9 that snails collected about 20 miles southeast of Great Falls have been identified as eastern heath snails (Xerolenta obvia), a species native to eastern Europe that spreads by attaching to cargo containers or other conveyances used in international shipping.

State and federal officials are surveying the surrounding area to determine the extent of the population and what actions might be appropriate.

This snail species has the potential to reduce crop yield and quality, contaminate fruits, vegetables, and hay, and transmit plant and animal diseases.

In a press release, MT Department of Agriculture director Ron De Yong noted, "We routinely conduct surveys for invasive pests that could damage crops or the environment. This discovery was unusual because the only other known instance of heath snails in the United States is in Michigan."

The photos above are courtesy of Ian Foley of the Montana Pest Management Bureau.

Eastern heath snails were found in 2001 in Detroit near a heavily trafficked shipping area adjacent to Ontario, Canada, where a larger population of the snails exists.

Xerolenta obvia is one of several snail species identified by USDA planning documents as a potential pest of U.S. agriculture, and control measures are recommended.

Heath snails lay eggs in the soil, infest a wide range of plant species including beans, peas, grapes and weeds, and can contaminate other crops such as grass hay and grain.

The eastern heath snail is slightly smaller than a dime in diameter and is white with dark brown spiral bands. They feed on a wide range of plants including alfalfa, clover, lupine, wheat, barley, fruit trees, and weeds.

This species is known for climbing on vegetation, fence posts, and other upright objects to escape high temperatures and will aggregate in enormous numbers in a behavior called massing.

The snails were observed during this massing behavior about 15 miles southeast of Great Falls along State Highways 200, 331, and 89. Individual snails numbered in the hundreds of thousands and may actually represent a population in the millions.

The snail prefers dry grassy areas and survives long periods of dry conditions by withdrawing into its shell and sealing the opening with a mucous membrane.