Rocky Mountain Capshell Snail (Acroloxus coloradensis): A Technical Conservation Assessment

Tamara Anderson
Posted on: 7/18/2022 - Updated on: 7/18/2023

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This assessment is one of many being produced to support the Species Conservation Project for the USDA Forest Service (USFS) Rocky Mountain Region. Acroloxus coloradensis (Rocky Mountain capshell snail) is the focus of an assessment because it is considered a sensitive species in Region 2. Within the National Forest System, a sensitive species is a plant or animal whose population viability is identified as a concern by a Regional Forester because of significant current or predicted downward trends in abundance and/or habitat capability that would reduce its distribution. A sensitive species requires special management, so knowledge of its biology and ecology is critical. This assessment addresses the biology of A. coloradensis throughout its range in Region 2. This introduction defines the goals of the assessment, outlines its scope, and describes the process used in its production.


Species conservation assessments produced as part of the Species Conservation Project are designed to provide forest managers, research biologists, and the public with a thorough discussion of the biology, ecology, conservation status, and management of certain species based on available knowledge. The assessment goals limit the scope of the work to critical summaries of scientific knowledge, discussion of broad implications of that knowledge, and outlines of information needs. The assessment does not seek to develop specific management recommendations. Rather it provides the ecological background upon which management must be based and focuses on the consequences of changes in the environment that result from management (i.e., management implications). Furthermore, it cites management recommendations proposed elsewhere and examines the success of those recommendations that have been implemented. Therefore, this assessment does NOT presume that the species deserves a specific conservation status, but rather provides a summary of information so management decisions can be made based on available data.


This assessment examines the biology, ecology, conservation status, and management of Acroloxus coloradensis with specific reference to the geographical and ecological characteristics of the USFS Rocky Mountain Region. Although some of the literature on the species originates from field investigations outside the region, this document places that literature in the ecological and social context of the central Rocky Mountains. Similarly, this assessment is concerned with behavior, population dynamics, and other characteristics of A. coloradensis in the context of the current environment rather than under historical conditions. The evolutionary environment of the species is considered in conducting the synthesis, but it is placed in a current context.

Producing the assessment involved reviewing refereed literature, non-refereed publications, research reports, and data accumulated by resource management agencies. Not all publications on Acroloxus coloradensis are referenced in the assessment, nor were all published materials considered equally reliable. The assessment emphasizes refereed literature, where possible, because this is the accepted standard in science. Non-refereed publications or reports were used when information was unavailable elsewhere, but these were regarded with greater skepticism. Unpublished data (e.g. Natural Heritage Program records, museum records, etc.) were especially important in estimating the geographic distribution. These data required special attention because of the diversity of persons and methods used in collection.


Acroloxus coloradensis (Rocky Mountain capshell snail) is considered a sensitive species in the USDA Forest Service Rocky Mountain Region (Region 2). This species is the only representative of Family Acroloxidae that resides in North America. Across its range, A. coloradensis is rare and has widely disjunct populations with some clusters of populations in Quebec, Colorado, and British Columbia. Only six locations are known in Region 2, including populations on the Routt and Roosevelt national forests.

Primary Threats

Acroloxus coloradensis resides in clean boreal lakes with rocky substrate. Because these lakes are critical habitat, some management activities have the potential to impact these populations. Primary threats include timber harvesting, pesticide application, fisheries management, and some recreational activities. Lowered water levels are a possible cause of the decline in one population.

Attached below is the final Assessment and an Assessment Update.


Anderson, T. (2005). Rocky Mountain Capshell Snail (Acroloxus coloradensis): A Technical Conservation Assessment. USDA Forest Service, Rocky Mountain Region.…

Affiliated Organizations

The U.S. Department of Agriculture Forest Service is a Federal agency that manages public lands in national forests and grasslands. The Forest Service is also the largest forestry research organization in the world, and provides technical and financial assistance to state and private forestry agencies. Gifford Pinchot, the first Chief of the Forest Service, summed up the purpose of the Forest Service—"to provide the greatest amount of good for the greatest amount of people in the long run."