Montana Field Guide

A distinctive medium to large-sized shell, to 22 mm diameter and 13 mm in height but usually smaller; flattened-heliciform, depressed somewhat in profile, with up to 5 3/4 whorls. Late whorls have coarse irregular striae and prominent raised spiral cords or lirae on both upper and lower surfaces (up to 5 above and 11 below the periphery). The umbilicus is narrow and deep (contained about 5 times in the diameter). The aperture is oval, periphery with a keel. Shell opaque and chalky, color is brownish-gray (dead shells to pearly white); Montana shells lack reddish-brown spiral bands often present in most other species of Oreohelix. Head, neck and tentacles dull ashy gray, darker than the shell (Hendricks 2012, Burke 2013). Internal anatomy is described by Pilsbry (1939) and Fairbanks (1975).

Possible subspecies: O. h. hesperia, O. h. hybrida, and O. h. perplexa in Idaho; O. h. oquirrhensis and O. h. bruneri in Montana.

The description of O. h. bruneri is based on shells from an unknown location in Montana and may not be valid; the material is apparently lost. Fairbanks (1975) felt that two of the four populations he studied in western Montana might be distinct at the subspecific level. With additional study, Montana Oreohelix haydeni may prove to be undescribed species. Included here are Oreohelix n. sp. 6 and n. sp. 31 of Frest and Johannes (1995). Oreohelix n. sp. 31 is considered by Frest and Johannes to be incorrectly attributed to O. h. oquirrhensis.

Late whorls have coarse irregular striae and prominent raised spiral cords or lirae on both upper and lower surfaces (up to 5 above and 11 below the periphery) which are distinctive for Montana Oreohelix.

Often associated with limestone talus and outcrops, sometimes with minimal tree canopy cover on steep south-facing slopes, although at least one site is north-facing. Primary canopy species include Douglas-fir, ponderosa pine, mountain maple; secondary canopy cover may include aspen, ninebark, and serviceberry. Live animals mostly under rocks and in duff or soil accumulations under rocks, sun-bleached shells may be found on the surface (Hendricks 2012).

Hermaphroditic (Pilsbry 1939 and Fairbanks 1975).

The known sites are on public (USFS, Bureau of Land Management) and private timberlands. None of these sites have special protection. As with many land mollusks, access to moisture is essential, even in arid locations, so favorable conditions include refugia that maintain high humidity and moderate temperatures for at least part of the year. Removal of forest and shrub canopy is likely detrimental.

Habitat occupied by Oreohelix haydeni (low-elevation slopes of open juniper, Ponderosa Pine and Douglas-fir) may be threatened by logging, grazing, weed control, highway development, home development, and fire. Logging and fire in the species' limited habitat, road construction and maintenance, and urban encroachment have already reduced existing populations, and drought has reduced its habitat (Frest and Johannes 1995). The impact of fire retardants on this and other terrestrial mollusks in not known. Little is known about this species, including its susceptibility to disturbance.