SPECIES FACT SHEET
Common Name: Pacific Walker
Scientific Name: Pomatiopsis californica (Pilsbry, 1899)
Phylum:
Class:
Order:
Family:
Mollusca
Gastropoda
Mesogastropoda
Pomatiopsidae
OR/WA BLM and FS Region 6 Units where Suspected or Documented:
Both the Forest Service and BLM have listed the Pacific Walker as a Sensitive
Species in Oregon.
The Pacific Walker has been documented on one National Forest in Oregon
(SIU). It is suspected to occur on one National Forest (RRS) and two BLM
Districts (CB, SA) in Oregon.
Status:
Natural Heritage Program Rank and Status:
 Oregon State Rank: S1; critically imperiled
List 1 - Threatened or endangered throughout range
 Washington State Rank: None
 National Rank: N1; critically imperiled
 Global Rank: G1; critically imperiled
State Status:
 Oregon State Status: None
 Washington State Status: None
Federal Status:
 None
Figure 1. NatureServe map of the conservation status of the Pacific Walker (Pomatiopsis californica) in the
United States and Canada. NatureServe 2009.
Technical Description:
This is a genus of very small, semi-aquatic snails. The Pacific Walker has a
shell moderately high, conical, and perforate, with 6-7 deeply and evenly
convex whorls; length 4 mm, aperture thin, definitely adnate; shell rather thin
with chestnut brown color (Frest and Johannes 2000). See Burch 1982 for
illustrations.
Life History:
The Pacific Walker is a small, semi-aquatic snail. It is characteristically found
among wet leaf litter and vegetation beside flowing or standing water in shaded
situations where humidity remains high (Taylor 1981). The biology of this
species is not well understood and needs further investigation. There are some
comments on the anatomy and ecology in Davis (1967).
Range, Distribution, and Abundance:
The Pacific Walker is a southwest Oregon and northwest California coastal
endemic with very limited range. The historic range includes the narrow
coastal fog belt of the Pacific Coast, from southwestern Oregon to northern San
Mateo County in California. The taxon Pomatiopsis chacei has been used as a
synonym for this species in northern California (Frest and Johannes 2000,
Taylor 1981).
In 1998, specimens resembling this taxon were noted by Frest from several
sites in Lincoln and Tillamook Counties, all within half a mile of the coast.
There is a possibility of more widespread occurrence; but searches in more
interior drainages, specifically in its narrow habitat, as well as the limited
nature of that habitat, suggest that the taxon will continue to be very rare and
confined to the coast with very limited potential range. It is quite sporadic and
scarce (Frest and Johannes 2000).
Frest and Johannes (2000) documented two sites for this species in Oregon.
One site is in the Lower Millicoma River sub-basin in northern Coos County,
approximately six miles from Coos Bay District BLM land, Umpqua Field Unit.
The second site is near the Pacific Coast in Lane County on the Waldport
Ranger District of the Siuslaw National Forest, in the Cape Creek
subwatershed of the Alsea River subbasin (Duncan, N. 2008).
Habitat Associations:
The Pacific Walker is a riparian associate semi-aquatic snail with very
specialized habitat. It is characteristically found among wet leaf litter and
vegetation, beside flowing or standing water in shaded situations where
humidity remains high (Frest and Johannes 2000).
Threats:
Habitat loss is a primary threat to the Pacific walker. Urbanization and
associated coastal modification, grazing, water diversion and ditching of
springs and seeps, and highway construction and maintenance all contribute
to habitat loss or degradation of this species.
Conservation Considerations:

Survey and map all Pacific walker occurrences.

Protect this species’ habitat from further destruction and restore it when
opportunities are presented.

Minimize or eliminate conversion of habitat for other uses.

Monitor and assess activities for impacts on the Pacific walker and its
habitat.

Monitor the effects of habitat changes on this species.

Minimize grazing access at known sites to protect from potential habitat
damage or impacts to water quality.
Other pertinent information:
Survey Protocol
While the Pacific walker was not a Survey and Manage species, the following is
a useful reference for conducting surveys of terrestrial mollusks.
Survey Protocol for Survey and Manage Terrestrial Mollusk Species from the
Northwest Forest Plan, Version 3.0 (2003)
http://www.blm.gov/or/plans/surveyandmanage/SP/Mollusks/terrestrial/Mo
llusk%20document.pdf
Preparer:
Theresa Stone
Umpqua National Forest
30 September 2009
Edited by:
Rob Huff
FS/BLM Conservation Planning Coordinator
January, 2010
References
Burch 1989. North American Freshwater Snails. Malacological Publications,
Hamburg, MI. 365 pp.
Davis 1967. The systematic relationship of Pomatiopsis lapidaria and
Oncomelania hupenensis formosana (Prosobranchia: Hydrobiidas). Malacologia
6: 1-143.
Duncan, N. 2008. Former Forest Service and BLM mollusk taxa specialist.
Personal communication.
Frest, T.J. and E. J. Johannes. 2000. Baseline Mollusk Survey of Southwest
Oregon (Rogue and Umpqua Basins). Deixis Consultants, Seattle, Washington.
Oregon Natural Heritage Program, Portland Oregon.
NatureServe. 2009. NatureServe Explorer: An online encyclopedia of life [web
application]. Version 7.1. NatureServe, Arlington, Virginia. Available
http://www.natureserve.org/explorer.
Pilsbry 1937. A California Pomatiopsis. The Nautilus 50: 84-85;
Taylor 1981. Freshwater mollusks of California: a distributional checklist.
California Fish and Game 67 (3): 140-163.
Turgeon, D.D., J.F. Quinn, Jr., A.E. Bogan, E.V. Coan, F.G. Hochberg, W.G.
Lyons, P.M. Mikkelsen, R.J. Neves, C.F.E. Roper, G. Rosenberg, B. Roth, A.
Scheltema, F.G. Thompson, M. Vecchione, and J.D. Williams. 1998. Common
and scientific names of aquatic invertebrates from the United States and
Canada: Mollusks. 2nd Edition. American Fisheries Society Special Publication
26, Bethesda, Maryland: 526 pp.