Land Mollusk Fauna of Montana: Biogeography, Conservation Status and Prospects

Scientific Disciplines
Biological Sciences - Terrestrial
University of Montana
Land snail
Snails & slugs
land snails
snails 8 slugs
land mollusk
Volume 16, No. 4

Land mollusk fauna of montana: Biogeography, 
conservation status and prospects

Paul Hendricks, Montana Natural Heritage Program, University of Montana, Missoula, Montana 
Approximately 78 species of land snails and slugs have been reported for Montana, 
contrasting to 93 for British Columbia, 85 for Idaho, and 43 for Wyoming.  Non-natives 
comprise 14 percent (4 snails, 7 slugs) of the total for Montana, 29 percent (13 snails, 14 
slugs) for British Columbia, 19 percent (5 snails, 11 slugs) for Idaho, and 7 percent (2 
snails, 1 slug) for Wyoming. Total native species for Montana, British Columbia and Idaho 
are nearly equal (67, 66, and 69, respectively), but only 40 for Wyoming, reflecting an 
overall drier and harsher climate. For Montana, 24 species (16 snails, 8 slugs) occur only 
west of the Continental Divide; the land snail fauna east of the Divide is 43 species, equal 
to the Wyoming total. Reflecting further the significance of western Montana for mollusk 
biodiversity, with its moister and more moderate climate, 15 of 24 exclusively western species 
(7 snails, 8 slugs) are Montana Animal Species of Concern, 5 of which (Discus brunsoni, 
Oreohelix alpina, O. amariradix, O. carinifera, O. elrodi) are Montana endemic snails. 
Land snails require cool and humid environments during their active season, microhabitats 
most prevalent in mature and old growth forests, riparian corridors, and around springs, but 
also present in large stable talus slopes. Many of these habitats are vulnerable to a variety 

of human-caused and natural disturbances. Some western Rocky Mountain populations are 
currently considered conspecific with Pacific Northwest coastal populations; genetic analyses 
are needed to determine if these are sister species, similar to results obtained for several 
amphibian taxa.