A STATE
THREATENED SNAIL SPECEIS FOUND IN DAIRYLAND POWER COOPERATIVE PROPOSED LANDFILL
PROJECT AREA, HARMONY TOWNSHIP, VERNON COUNTY, WISCONSIN
James L.
Theler, Ph.D
Department
of Sociology and Archaeology
University
of Wisconsin-La Crosse
La Crosse,
WI 54601
Email:
theler.jame@uwlax.edu
During October 2007, I visited
the two site areas selected by Dairyland Power Cooperative for a proposed
landfill to hold toxic fly ash. During my visits I located two colonies of a
state threatened land snail, the cherrystone drop, which has the scientific
name of Hendersonia occulta (Say, 1831). This species is a living
relict of the last Ice Age or Pleistocene period that ended about 12,000 years
ago. It was first described from sub-fossil shells that are widespread in Ice
Age deposits, but its’ known range in historic times is very limited with a
relatively small number of surviving isolated colonies known. The shell of this
species is about the size and shape of a cherry pit, thus its’ name. The shell
is about one-quarter inch in diameter and is most often a distinctive cinnamon
red to reddish brown.
According
to the Wisconsin DNR, the cherrystone drop has a “State Element Rank” of S-3.
The Key to Wisconsin Natural Heritage Working List states that: “S-3=Rare or
uncommon in Wisconsin (21 to 100 occurrences). ”
http://dnr.wi.gov/org/land/er/wlist/key.htm#WIStatus. The cherrystone drop
snail is known from two colonies in Michigan (Michigan Natural Features
Inventory), a few counties in southwestern Pennsylvania, and very sporadic
occurrences in the southern Appalachians.
(http://carnegiemnh.org/mollusks/palandsnails/accounts/he_occu.htm).
In Wisconsin the largest number
of cherrystone drop snail colonies concentrated along the Niagara Escarpment in
eastern Wisconsin and in the Driftless Area of southwestern Wisconsin. The
habitat for this species is generally rocky, moist, shaded deciduous woodlands
with a humus layer and calcareous soil. As discussed in the Michigan Natural
Features Inventory (2004), the cherrystone drop is “highly vulnerable to habitat
loss and disturbance, such as timber harvesting…and disruption of geological and
hydrological conditions and dynamics.”
References: