Plants and Animals

Pomatiopsis cincinnatiensis Brown walker

Key Characteristics

The brown walker is a small freshwater snail with a broadly conic shell that is 4.5 mm in height and 3.5 mm wide with rounded whorls gradually increasing in size and a small rounded aperture (main opening) 1/4 the height of the shell with the outer margin thickened and folded back. A small opening (umbilicus) lies on the bottom of the central shell axis. The operculum (lip covering the main opening) is paucispiral (having a few broad spirals).

Status and Rank

US Status:
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G4 - Apparently secure
State Rank: SH - Possibly extirpated

Occurrences

CountyNumber of OccurrencesYear Last Observed
Berrien21955
Jackson11970
Kent2
Lenawee61955
Manistee1
Monroe71960
Van Buren21954
Washtenaw41970
Wayne1

Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.

Habitat

The brown walker inhabits the banks of medium to large rivers. It is thought to prefer clay river banks and may hibernate on moist banks above water, under leaf litter and dormant grassy vegetation. It lives on wet ground primarily along the edges of streams.

Natural Community Types

  • Floodplain forest
  • Mainstem stream (3rd-4th order), pool
  • Mainstem stream (3rd-4th order), run

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management Recommendations

The brown walker likely depends on maintaining natural vegetative canopy cover along stream banks. Thus, cutting and clearing of trees and herbaceous vegetation along streams should be avoided. The species may also benefit from periodic flood events. The species also is likely susceptible to water pollution in the form of pesticides as well as urban runoff and municipal discharge.

Active Period

Active from first week of June to second week of October

Survey Methods

This species can be surveyed using several techniques. One survey method consists of sweeping aquatic vegetation or scraping the substrate with a fine mesh aquatic sampling net or dip net (e.g., D-frame net) anytime from late September through December, but earlier surveys also would likely be effective. Another survey technique consists of vigorously shaking aquatic vegetation over a pail of water causing the various snails clinging to the plants to drop to the bottom of the pail. Visual surveys also can be conducted for this species by looking for snails attached to vegetation, rocks, woody debris and other cover. Glass bottomed buckets may be used to see snails clinging to vegetation or rocks underwater. Rocks, vegetation, and other cover also should be picked up, examined for snails, and returned to their original positions.

Sweeping with dip net

Survey Period: From first week of June to second week of October

Visual survey

Survey Period: From first week of June to second week of October

Shaking vegetation survey

Survey Period: From first week of June to second week of October

References

Survey References

  • Berry, E.G. 1943. The Amnicolidae of Michigan: Distribution, Ecology, and Taxonomy. University of Michigan Press, Ann Arbor. 68pp.
  • Clarke, A.H. 1981. The Freshwater Molluscs of Canada. National Museum of Natural Science, National Museums of Canada, Ottawa. 446pp.

Technical References

  • Berry, E.G. 1943. The Amnicolidae of Michigan: Distribution, Ecology, and Taxonomy. University of Michigan Press, Ann Arbor. 68pp.
  • Clarke, A.H. 1981. The Freshwater Molluscs of Canada. National Museum of Natural Science, National Museums of Canada, Ottawa. 446pp.
  • Environmental Protection Agency. 1982. Freshwater Snails (Mollusca: Gastropoda) of North America. EPA Publication 600/3-82-026. Environmental Monitoring and Support Laboratory, Office of Research and Development, U.S. EPA, Cincinnati. 294pp.