Rare Species Guide

  Basis for Listing

The bluff vertigo is a rare landsnail found in a small number of sites in southeastern Minnesota, northeastern Iowa, central Missouri, and recently Illinois. This taxon was more widespread during the Wisconsin glacial period (>12,000 years ago), but it now survives only as small relict populations with very specific habitat requirements. In Minnesota, it is known to occur at only six sites in Olmsted, Winona, and Wabasha counties. All known sites are small and/or confined to narrow portions of relict sites, and few of the sites are protected. The rarity of this species led to its classification as a threatened species in Minnesota in 1996.

  Description

The bluff vertigo has a small shell, up to 2.11 mm (0.08 in.) with 3.5-5 whorls. The shell is a slowly expanding spire with the last whorl wider than penultimate. All whorls are distinctly but weakly striate. There are usually 5 teeth, which are white. The bluff vertigo is deep cinnamon red in color (Frest 1991).

  Habitat

The bluff vertigo occurs on forested, limestone or dolomite cliffs and outcrops, generally on steep, moist, shaded, and cool north-facing slopes. It has been found on algific slopes and maderate cliffs, but it generally avoids the continuous cooling effects in these types of habitats. On non-algific sites, the species is often confined to cliff bases and the lowermost 6 m (20 ft.) of the cliff face. In these areas, it is particularly abundant in the finely pelleted soil of rodent runs. Common plant associates are maples (Acer spp.), conifers, and yews (Taxus spp.) (Frest 1991).

  Biology / Life History

The bluff vertigo usually stays hidden under leaf litter or in rock cracks, but during wet conditions it may climb freely over rock surfaces (Frest 1991).

  Conservation / Management

Land use activities that could compact the talus soil of landsnail habitat and crush the snails themselves, including grazing, hiking, and use of heavy equipment for timber harvest or vegetation clearing, should be carefully managed. Application of pesticides, herbicides, and fertilizers can alter the flora in landsnail habitat and may be toxic to the snails. To protect the bluff vertigo, upland buffer zones should be established and maintained around sites where it occurs. These areas should be protected from human traffic, grazing, and vegetation clearing. Since the bluff vertigo is not as dependent on cold air or water flow as other Vertigo species, it is less susceptible to the disturbance of such flows. Populations and habitat quality should be monitored at sites where the bluff vertigo is known to occur.

  Conservation Efforts in Minnesota

The bluff vertigo was first discovered in Minnesota at two sites in 1989. In 1990, the DNR's Nongame Wildlife Program funded a survey of algific slope and maderate cliff sites for rare plant and landsnail species. Four additional populations of bluff vertigos were discovered during this survey (Ostlie 1990).

  References and Additional Information

Barthel, M., and J. C. Nekola. 2000. Scanning electron microscope imaging of minute land snails of Minnesota. Final report submitted to the Natural Heritage and Nongame Research Program, Minnesota Department of Natural Resources.

Frest, T. J. 1991. Summary status reports on eight species of candidate land snails from the driftless area (Paleozoic Plateau), Upper Midwest. Final report submitted to the U.S. Fish and Wildlife Service, Region 3. 54 pp.

Ostlie, W. R. 1990. Completion of the algific slope/maderate cliff landsnail survey in Minnesota. Final report submitted to the Division of Ecological Services, Minnesota Department of Natural Resources, St. Paul.. Unpaged.