Dalles sideband (snail) (Monadenia fidelis minor)

Physical description

Taxonomic note: Dalles sideband is in the family Bradybaenidae.

Ecology and life history

The Dalles sideband has been found in moist talus habitat (especially around seeps and springs), and in forested areas in upland sites near, but outside of, riparian corridors. In some forested sites, the species has been found associated with down wood where no rock substrates occur. Down wood may provide temporary refugia used during dispersal in the wet season, while rock substrates provide more stable refugia used for estivation during summer and winter and during fire events.

Land snails are hermaphroditic and exchange gametes with other conspecific individuals when conditions are favorable, typically in the spring, and then both will lay eggs in damp subsurface situations where the eggs will be relatively safe from predators and desiccation. Land snails do not tend their eggs or young. There is no larval stage and newborn snails look like miniature adults (the innermost part of the shell develops within the egg).

Snails need moisture, so where the habitat dries out, they will estivate in the summer, become active with fall rains, and hibernate when the season turns cold.

Land snails eat plants (living or dead), fungi, fruit, microorganisms, litter, wood, and dead animals.

Loose soil may be necessary for egg-laying by sideband snails, which lay several dozen eggs; they are likely to live more than six years, and probably mature in two years. During the moist spring and fall seasons, Dalles sidebands may be found in the open, away from refugia. Daily refugia used during moist seasons can be down wood, rock or accumulations of litter.

During the summer, snails are found deep in talus accumulations which are adjacent to springs or streams and which serve as refuge sites from desiccation and protection from predators while the snails are immobile. These deep rock refugia also provide the important, environmentally stable sites needed to survive wildfire events and cold winter conditions.

Mollusks which inhabit talus habitats also utilize the surrounding forest areas during moist, cool conditions, ranging out from the refugia provided by the rocks to forage in the adjacent forest floor litter.

Geographic range

This species is known from the Columbia Gorge from Hood River east to the vicinity of The Dalles on both sides of the Columbia River and in upland sites in the lower Deschutes River watershed within Mt. Hood National Forest in Wasco County, Oregon.

The species may have occurred historically in the central and part of the eastern Columbia Gorge and south up the Deschutes River Valley as far as 50 miles from the confluence.

A total of 98 sites are known, but most sites are in Oregon, and only a few individuals have been found at most sites. Known sites are widely scattered across the species’ range and separated by non-habitat.

The distribution of stable rock refugia sites across the landscape may determine or help to explain the distribution of the species in areas with short fire-return intervals.

For a map of range-wide distribution and conservation status of this species, check out NatureServe Explorer.