Montana Field Guide

Shell is low-domed heliciform, 7-13 mm diameter (types 9.3 and 9.4 mm), height of types 6.1 and 6.3 mm. Color cinnamon to snuff brown, from third whorl profusely marked with white patches and narrow streaks; last whorl having a chocolate band below the periphery. Shell surface is somewhat wrinkled and shows traces of spiral striation in places. Shell to about 4.4 whorls, all convex. Embryonic shell of nearly 2 whorls, which are finely striate and covered with very fine spirals, the last half of the second whorl having distinct spiral striae. Umbilicus narrow, contained 5.5 times in the diameter of the shell (Pilsbry 1939; Frest and Johannes 1993; Burke 2013). Internal anatomy described by Pilsbry (1939).

Active in wet and cool weather; otherwise not described.

Small size (< 13.0 mm diameter), range and habitat separates this species from most other Oreohelix in Montana. Similar in size and appearance, as well as range and habitat, to Oreohelix pygmaea but with weaker growth wrinkles and spiral striae, lower spire (not bee-hived shape) and a smaller umbilicus (Burke 2013).

Sedentary.

Found among small loose rock, shrubbery, and under Creeping Juniper (Juniperus horizontalis) on west-facing canyon slopes at the type locality in the Big Snowy Mountains, and under sticks and logs in moister locations in the same mountain range (Berry 1916). This snail was present in the Mammoth area of Yellowstone National Park on a north exposure of limey soil with plenty of cover, but neither very wet nor dry (Henderson 1936). Substrate typically is derived from limestone (Frest and Johannes 1993, 1995). In the Black Hills and Bear Lodge Mountains of Wyoming and South Dakota, it occurs in mixed and open Ponderosa Pine (Pinus ponderosa) forests with relatively thin litter, often with aspen (Populus tremuloides) and birch (Betula) in the canopy, and violets (Viola) and Bunchberry Dogwood (Cornus canadensis) in the understory (Frest and Johannes 1993); the deciduous tree component was relatively important for the occurrence of this subspecies.

Feeds on deciduous tree components (Frest and Johannes 1993).

Oreohelix strigosa berryi in Montana has been fully documented only in the Big Snowy Mountains. Population sizes are not reported for any of the Montana locations, nor have most of these sites been revisited in recent decades. Berry (1916) found it to be the most conspicuous land snail near the mouth of Swimming Woman Creek Canyon in the Big Snowy Mountains. Colonies outside of the Big Snowy Mountains generally appear to be small and isolated (Frest and Johannes 1993), although the recent collection of shells in the Judith Mountains (P. Hendricks unpublished data) indicates colonies, some fairly large, may be present in some of the other "island mountains ranges" of eastern Montana. Henderson (1936) said the species occurred in abundance near Mammoth in Yellowstone National Park, Wyoming. Population trends are unknown for any locality.

Colony lengths of a mile and widths of 1/4-1/2 mile are known from several states.

Most individuals breed once, but under extremely wet conditions, young could be released twice in the same year (Frest and Johannes 1993). In many cases, breeding takes place in October-November or by April-May, and young are shed in May-June or September-October. The young hatch internally and can be retained in the adult for some time after internal hatching; this unusual ability is believed to be an adaptation for xeric living conditions. Growth to adulthood commonly requires just under one year (Frest 1991).

The type locality (Swimming Woman Creek Canyon) and all other known locations (six total) in the Big Snowy Mountains are on lands administered by the Musselshell Ranger District of the Lewis and Clark National Forest. Two other sites north of the Big Snowy Mountains apparently are on private and possibly state land. The site in the Judith Mountains is on land administered by the Lewistown Field Office of the Bureau of Land Management. The Park County site is on land administered by the Livingston Ranger District of the Gallatin National Forest.

Habitats occupied by Oreohelix strigosa berryi are may be threatened by logging and grazing, and possibly weed control and mining, but most documented localities have not been revisited in decades, so current threats are unknown. Fire and fire suppression efforts could have negative impacts (numerous dead shells found in the Judith Mountains were in a decade-old burn). Logging and grazing threaten the Black Hills National Forest colonies (Frest and Johannes 1993). Habitat requirements and food habits are poorly understood. Colonies may be local and small.