(DRAFT) - Taxonomy
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
TAXONOMY
NAME - SNAIL, PLEISTOCENE, IOWA
OTHER COMMON NAMES - SNAIL, PLEISTOCENE and IOWA
ELEMENT CODE -
CATEGORY - Aquatic Molluscs
PHYLUM AND SUBPHYLUM - MOLLUSCA,
CLASS AND SUBCLASS - GASTROPODA,
ORDER AND SUBORDER - STYLOMMATOPHORA,
FAMILY AND SUBFAMILY - DISCIDAE,
GENUS AND SUBGENUS - DISCUS,
SPECIES AND SSP - MACCLINTOCKI,
SCIENTIFIC NAME - DISCUS MACCLINTOCKI
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Iowa Pleistocene Snail
Discus macclintocki (Baker, 1928)
KINGDOM: Animal GROUP: Snail
PHYLUM: Mollusca CLASS: Gastropoda
ORDER: Stylommatophora FAMILY: Discidae
The Iowa Pleistocene snail (Discus macclintocki (Baker)) is an
average-sized Discus and adults are 6-8 mm wide. The moderately
high-spired shell is tightly coiled and adults typically have six
whorls. Shell color is either brown or greenish-white and the ribs
are relatively fine and confined to the upper half of each whorl. The
species has a moderate-sized umbilicus and lacks a parietal callus
(01). Photographs are included in the Recovery Plan (01).
The first description of the species is of two forms (02), the
nominate subspecies and D.m. angulatus. Both were named from fossils
so the distinguishing features are conchological only. D.m. angulatus
is said to be more depressed and more widely umbilicate and to have a
subangular periphery. Both subspecies were accepted by Pilsbry (03)
and in living populations are present equally as frequent (01).
Taxonomy - 1 (DRAFT) - Status
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
STATUS
Coded Status
E: Federal Endangered
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The Iowa Pleistocene snail (Discus macclintocki) has been
designated an Endangered species pursuant to the Endangered Species
Act of 1973 (50 CFR 17.11; P.L. 93-205, 87 Stat. 884; 16 U.S.C.
1531-1540), as amended. The species has this status wherever found
including the States of Illinois, Indiana, Iowa, Kansas, Minnesota,
Missouri, Nebraska, Ohio, and Wisconsin.
This species is protected by the Lacey Act (P.L. 97-79, as
amended; 16 U.S.C. 3371 et seq.) which makes it unlawful to import,
export, transport, sell, receive, acquire, or purchase any wild animal
(alive or dead including parts, products, eggs, or offspring):
(1) in interstate or foreign commerce if taken, possessed,
transported or sold in violation of any State law or
regulation; or
(2) if taken or possessed in violation of any U.S. law,
treaty, or regulation or in violation of Indian tribal law.
It is also unlawful to possess any wild animal (alive or dead
including parts, products, eggs, and offspring) within the U.S.
territorial or special maritime jurisdiction (as defined in
18 U.S.C. 7) that is taken, possessed, transported, or sold in
violation of any State law or regulation, foreign law, or Indian
tribal law.
RESPONSIBLE FEDERAL AGENCIES:
USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.
Status - 1 (DRAFT) - Status
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
All Federal agencies have responsibility to ensure that any
action authorized, funded, or carried out by that agency is not likely
to jeopardize the continued existence of the species or result in the
destruction or adverse modification of Critical Habitat (50 CFR 402),
and to utilize their authorities to carry out programs for the
conservation of the species.
STATE STATUSES AND LAWS:
STATE: Illinois, Indiana, Iowa, Kansas, Minnesota, Missouri,
Nebraska, Ohio, and Wisconsin.
DESIGNATED STATUS: Recognized Endangered
ADMINISTRATIVE AGENCY: (IL) Endangered Species Protection Board,
Illinois Department of Conservation;
(IA) Conservation Commission, Iowa
Division of Fish and Game;
(IN) Department of Natural Resources;
(KS) Fish and Game Commission;
(MN) Department of Natural Resources;
Division of Game and Fish;
(MO) Conservation Commission, Missouri
Department of Conservation;
(NE) Game and Parks Commission;
(OH) Department of Natural Resources;
(WI) Department of Natural Resources.
STATE STATUTES: (IL) Administrative Code 1010.30, Smith-Hurd IL
Annotated Statutes, Chapter 8, Sec. 331 to 340;
(IN) Statutes Annotated 14-2-8-8.5-1, 310 IN
Administrative Code 3-3-6;
(IA) Administrative Code, Chapter 109A.1, and
109A.5;
(KS) Statutes Annotated 32-502(d), (j), 504;
(MN) Code of Agency Rules 1.5600 to 1.5601, MN
Statutes Annotated 97.40, 97.43, 97.488 and
98.45;
(MO) Revised Statutes 252.240, 3 Wildlife Code
of MO 10-4.111;
(NE) Rev. Stat. 37-430 to 438, Neb. Admin. Rules
and Regs. Vol. 13, 6-(1)(d), 6-(10), 1981;
(OH) Revised Code Annotated 1531.25, Ohio
Administrative Code 1501:31-23-01;
(WI) NR 27.03 WI Administrative Code.
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
None.
ECONOMIC STATUSES:
None.
77/07/14:42 FR 36420/36431 - Republication of Endg. & Thr. Spec. list
78/07/03:43 FR 28932/28935 - Listing as Endangered
Status - 2 (DRAFT) - Status
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
80/05/20:45 FR 33768/33781 - Republication of list with corrections
83/12/08:48 FR 55100/55101 - Five year review
Status - 3 HABITAT ASSOCIATIONS
HABITAT - TERRESTRIAL
TERRESTRIAL
SOCIETY OF AMERICAN FORESTRY TYPES
SAF TYPE STAGE CLOSURE
young tree
mature tree
Old Growth
Aspen-paper birch young tree
Aspen-paper birch mature tree
Aspen-paper birch Old Growth
LAND USE -
Cropland and Pasture
Deciduous Forest Land
COMMENTS ON HABITAT ASSOCIATIONS -
At present the only suitable habitat for D. macclintocki is on
certain portions of algific (cold-producing) talus slopes, a term
coined by Frest (04), to describe a type of habitat in the Driftless
Area of Iowa, Minnesota, Wisconsin, and Illinois. Algific slopes are
developed over the entrances to small fissures and caves. Air
circulation and groundwater infiltration from the surface produces
more or less permanent underground ice whose incomplete melting
produces a constant stream of moist cool air which filters through
a thin plant and litter cover over an extensive rock talus.
Algific slopes are most likely to occur in large porous carbonate
rock units that cap eroded slopes and are underlain by a geologic unit
relatively impervious to ground water flow. Such cliff-forming units
as the limestones of the Ordovician Prairie du Chien Formation and
Galena Group and the dolomites of the Silurian Hopkinton Formation
are ideal. Mechanical karst terrain does not develop well in the
sandstone cliffs of the St. Peter or Trempleau Formations.
Dolomitized or mineralized portions of the Galena Group (e.g., the
Upper Mississippi Valley lead-zinc mining district of Iowa, Illinois,
and especially Wisconsin) are apparently unsuitable.
Periglacial effects are most pronounced in the Driftless Area on
steep, north-facing slopes along the escarpments, and nearly all
algific slopes meet these criteria. They function as refugia because
the talus is left permanently cool and moist. Even in hot summers,
ground temperature seldom exceeds 10 degrees C or in winter, falls
much below minus 10 degrees C (04,05); average humidity often exceeds
60 percent. Algific slopes are believed to provide a buffered
microclimate that is analogous to that prevalent in the glacial range
of the Iowa Pleistocene snail.
These slopes are most often covered with hardwood deciduous trees
(01). Iowa Pleistocene snails prefer white and yellow birch (Betula
papyrifera and B. allegheniensis) leaves and also those of hard
maples, trees with limited distribution in Iowa and Illinois (01).
As per casual observation, it is believed that individuals prefer
leaf litter with a high proportion of certain types of deciduous
leaves and typically avoid areas with moss ground cover or coniferous
needle litter (01). Eggs are laid under logs and bark in protected
moist rock crevices and in the soil a short distance beneath the
surface (01). Land use in the surrounding area for pasture is very
common in these agriculture oriented States. At some of the known
sites there are single line utility poles traversing the habitat and
Habitat Associations - 1 at one site there is a access trail for four-wheel drive vehicles
leading to a logging area.
In general, it must be noted that any surface or subsurface
modification to the slope itself or to the related fissures, sinks,
and caves on the slope above, could adversely impact a colony or
result in extinction of a colony.
Habitat Associations - 2 (DRAFT) - Food Habits
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
FOOD HABITS
TROPHIC LEVEL -
HERBIVORE
LIFESTAGE FOOD FOOD PART
General Deciduous Shrubs-Leaves/Twigs
General Deciduous Trees-Leaves/Twigs
Food Habits - 1 (DRAFT) - Environment Associations
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G
G Terrestrial Features: Depressions
G Terrestrial Features: Talus
G Terrestrial Features: Cliffs/ledges
G Terrestrial Features: Rock outcrops
G Terrestrial Features: Downed logs
G
Environment Associations - 1 (DRAFT) - Life History
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
LIFE HISTORY
FOOD HABITS:
Iowa Pleistocene snails prefer white and yellow birch (Betula
papyrifera and B. allegheniensis) leaves and also those of hard
maples, trees with limited distribution in Iowa and Illinois (01).
They will also eat dogwood and willow leaves but refuse a wide
variety of food sources commonly used by other land snails (04).
HOME RANGE/TERRITORY:
The species is non-territorial and occurs in small groups or
larger colonies (01).
PERIODICITY:
Iowa Pleistocene snails remain active all year long but have a
period of greater activity from January to October (01). Individuals
semi-hibernate in October as they retreat into the soil for the winter
season (01).
MIGRATION PATTERNS:
Because of the snails' limiting temperature and moisture
requirements, successful migration is nil and such normal avenues as
stream transport and hoarding or collection by small animals are
ineffective (01).
COVER/SHELTER REQUIREMENTS:
The snails need well developed leaf litter for cover, food and
protection from dessication (01).
REPRODUCTIVE SITE REQUIREMENTS:
As per casual observation, it is believed that individuals prefer
leaf litter with a high proportion of certain types of deciduous
leaves and typically avoid areas with moss ground cover or coniferous
needle litter (01). Eggs are laid under logs and bark in protected
moist rock crevices and in the soil a short distance beneath the
surface (01). Sites chosen are cool and the temperature is fairly
stable with relative humidity about 60% (01).
REPRODUCTIVE CHARACTERISTICS:
Iowa Pleistocene snails reach sexual maturity at 2-2.5 years and
breed until death (01). The breeding season is late March to April
through August in wild populations (01). The receptive period of the
female-male is variable and multiple broods from one individual per
year are common (01). The species is hermaphroditic but not
self-fertilizing and all adults can lay eggs and fertilize others
(01).
Hatching of eggs occurs about 28 days after they are laid.
Average number of eggs laid varies from 2-6 with 3 being typical.
About 90% of these commonly hatch (01).
POPULATION BIOLOGY:
Habitat availability, suitability, and destruction are the major
current limiting factors of the snail. Presently the species occurs
Life History - 1 (DRAFT) - Life History
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
in only about 22 small areas in northeast Iowa and northwest Illinois,
and 50% of the individuals are in 4 colonies. Only about 40,000
individuals remain and this density varies from year to year (01).
Individual snails live an average of 5 years although 6 or 7
years is possible (01). Mortality rates are undocumented but major
causes are dessication of juveniles and shrew predation of adults
(01). A typical proportion of juveniles to adults in a colony is
6:1 (01).
It is estimated that the critical recruitment number is 50-150
individuals (01).
SPECIES INTERRELATIONSHIPS:
Predation by shrews (Blarina brevicauda) is a major cause of
adult mortality (01).
OTHER LIFE HISTORY DESCRIPTORS:
Iowa Pleistocene snails are associated with the threatened
northern wild monkshood (Aconitum noveboracense) (01).
Life History - 2 (DRAFT) - Management Practices
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Controlling/Restricting Off-Road Vehicles
Beneficial Restricting/regulating human disturbance of populations
Beneficial Maintaining/Controlling Water Flow
Beneficial Controlling/Restricting Mining
Beneficial Maintaining undisturbed/undeveloped areas
Beneficial Land Acquisition
Beneficial Controlling pollution [thermal, chemical, physical]
Beneficial Controlling/Restricting Pesticide Use
Beneficial Controlling/Restricting Herbicide Use
Beneficial Reforestation
Beneficial Restricting Timber Harvest
Beneficial Stocking captive-reared wild-strain animals
Beneficial Transplanting wild animals
Beneficial Controlling/Removing Domestic Animals
Adverse Incidental Capturing/Killing
Existing Incidental Capturing/Killing
Adverse Rock Climbing
Existing Rock Climbing
Adverse Hiking/Camping
Existing Hiking/Camping
Adverse Predation
Existing Predation
Adverse Surface Mines
Existing Surface Mines
Adverse Rural Residential/Industrial Areas
Existing Rural Residential/Industrial Areas
Adverse Highway/Railroads
Existing Highway/Railroads
Adverse Transmission Lines/Towers
Existing Transmission Lines/Towers
Adverse Soil compaction by heavy equipment in mine areas
Existing Soil compaction by heavy equipment in mine areas
Adverse Climate Alteration
Existing Climate Alteration
Adverse
Existing
Adverse Erosion
Existing Erosion
Adverse Grazing
Existing Grazing
Adverse
Existing
Adverse Forest Alteration
Existing Forest Alteration
Adverse Harvesting
Existing Harvesting
Management Practices - 1 (DRAFT) - Management Practices
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
COMMENTS ON MANAGEMENT PRACTICES -
The major long-term cause of decline of the Iowa Pleistocene
snail is cyclic climatic changes. If glacial conditions were to
return it would likely recolonize a major part of the upper Midwest
(01).
Presently, human disturbance is the most important cause of
decline. Loss of habitat due to slope clearing, removal of trees for
pasturing and lumber, road building, and powerline construction have
been detrimental to the population. Pasturing leads to trampling of
snails and erosion, and human traffic (hiking and rock climbing)
causes compaction of litter and crushing of snails (01). Subsurface
modification such as quarrying and house construction have also
eliminated important habitat of the species (01).
Natural calamities have also caused the species to decline.
Rockfalls, stream under-cutting, and treefalls can cause major habitat
change or destruction (01). Biotic factors that are restricting the
population include predation by shrews, which is a major cause of
adult mortality. Unusually severe winters or summers also prove
detrimental to the population (01).
Interglacial populations of the Iowa Pleistocene snail represent
only a small fraction of glacial numbers. The species is a normal
component, sometimes a dominant one, of the Pleistocene glacial
Midwest Biome. In single fossil sites, especially in the Peoria
Loess, millions of individuals are preserved. In interglacial
periods, algific slopes provide the most analogous climate (01).
Thus the major long-term cause of decline is cyclic climatic
change. The species has survived several such cycles in the past,
however. With a return to glacial conditions it could be resuscitated
over a major part of the upper Midwest, provided its relictual areas
are preserved and maintained.
Once the necessary algific talus slope terrain develops near the
close of a glacial epoch, geologic factors become comparatively
unimportant. Interglacials are short enough, and erosion slow enough,
that degradation and loss of habitat due to large-scale geologic
processes is probably minor (01).
The most important causes of decline of Iowa Pleistocene snail
interglacial habitat is human disturbance. It is estimated that about
a 75 percent loss of habitat has occurred in the last 150 years (01).
Slope clearing is a major factor. Removal of trees, even without
concommitant effects, destroys the major food sources, lessens litter
accumulation, and leaves the slopes more exposed to seasonal
temperature extremes. Clearing is conducted for pasturing, to obtain
lumber, and to facilitate road building. In a few cases, powerline
construction was the motivation (01).
Pasturing of domestic animals, particularly cows, has obliterated
a number of suitable slopes. They are fragile and subject to
trampling damage. Because algific slopes are often too steep and
rocky for tillage, and not ideal locales for economically valuable
tree species, many have been used as pastures. Much of the
potentially suitable habitat in Wisconsin has been pastured. The
overall effect, aside from obliterating the unique biota, is to
increase soil erosion. Most slopes are overgrazed and unstable under
current weather conditions if vegetation is removed (01).
Management Practices - 2 (DRAFT) - Management Practices
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
Human traffic is also a major cause of damage to many algific
slopes. The damage is due to denudation of inhabited stretches due
to rock falls, but also to compaction of litter and crushing of snails
by trampling. At least seventy of the known slopes show some damage
attributed to foot traffic. Among the instances observed were
hunters, casual hikers, plant and mushroom collectors, and researchers
on algific slope biota. Scientific or amateur collecting and field
study must be included and causes appreciable damage.
Road building, either for vehicular travel or to allow easy
access to hilltop fields, has also caused considerable attrition of
slopes. Aside from damage to the litter cover, any disruption of the
air circulatory system is potentially disastrous (01).
Subsurface modifications such as quarrying also eliminate
habitat by a combination of physical destruction of the surface and
disruption of the subsurface ice cave or fissures. Other examples in
this category include house construction, installation of sewer lines
or other underground pipelines, mining and drainage excavations (01).
In general, it must be noted that any surface or subsurface
modification to the slope itself or to the related fissures, sinks,
and caves on the slope above, could adversely impact a colony or
result in extinction of a colony. Some observed activities (although
difficult to assess) include: 1) waste disposal (solid or liquid) on
talus slopes or sinks in adjoining fields; 2) herbicide damage; and
3) pesticide damage. No major instances of deliberate vandalism have
yet been observed, but are a possibility to be considered (01).
Several natural factors have been observed to damage algific
slopes. In no instance has destruction of an entire slope occurred
and damage is usually limited in areal extent. Most are also not
readily preventable, but because some colonies are small, attempts to
repair such damage to D. macclintocki sites are warranted and
feasible (01).
Small-scale geologic processes such as rockfalls and stream
undercutting have damaged algific slopes by burying critical portions
or physically removing small areas (01).
Predation by shrews is a major cause of adult mortality. The
same factor operates on most land snails above a certain size, and
should not normally be a major (limiting factor) cause for concern.
Trampling by deer and other traffic causes minor damage, but the
tendency for animal trails to be narrow and rather constant in
location on the slopes limits possible damage. Tree falls in critical
areas likewise can cause severe but highly localized damage.
Predation by cychrine beetles as a cause of mortality at one colony
has been noted. This contribution to juvenile mortality remains
unassessed (01).
Unusually severe winters or summers undoubtedly cause major
damage from time to time. The influence of cold air drainage can
be counteracted by these severe events. Such are unlikely to cause
complete extinction, however; the Iowa Pleistocene snail survived the
so-called Altithermal or Hypsithermal, a period of unusually warm and
dry weather which occurred at about 6,000 years before present.
Tornadoes or lightening strikes also cause damage to individual
colonies. Forest fires may be a problem, if severe, but the cool and
moist slopes are reasonably insulated from direct fire damage.
Management Practices - 3 (DRAFT) - Management Practices
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
Changes to vegetation and soil chemistry of surrounding areas could
have a major impact (01).
APPROVED PLAN:
U.S. Fish and Wildlife Service. 1984. National Recovery Plan for the
Iowa Pleistocene Snail (Discus macclintocki (Baker)). U.S. Fish and
Wildlife Service, Twin Cities, MN. 26 pp.
The primary objective of the Recovery Plan is to remove the Iowa
Pleistocene snail from Endangered status. The most important feature
of the plan is the protection of existing colonies by:
1) Gaining control of relevant algific talus slopes; and
2) Protecting these slopes from human disturbances. Existing talus
slope areas and adjacent upland mechanical karst must be restored to
their original state, maintained, and stringently protected.
Secondly, to establish a sizeable and dispersed biologically viable
population, reintroduction efforts should be made. Finally, in order
to ensure the success of both recovery efforts, a monitoring program
should be set up to document positive response to protection efforts.
Specific recovery actions include:
1) Habitat Protection.
a) Potential habitat should be surveyed for new colony sites.
b) Requirements for upland buffers should be determined to reduce
protection costs. Upland areas requiring protection include
sinks, sinkholes, fissures and subsurface components.
Deforestation, pesticide/herbicide use, filling and blocking of
sinkholes by waste or garbage disposal are potential hazards
(i.e., any increase or decrease in water and air flow or
deterioration of groundwater input to the algific (talus)
slopes is a hazard).
c) Interagency agreements for habitat protection should be
established for colony sites.
d) Evaluate and implement land protection strategies for colony
sites including limiting human and cattle disturbance, limiting
development and/or mining, land acquisition (fee title,
easement, lease, cooperative agreement, etc.), restricting
timber harvesting activities, and fencing and signing of areas
to limit access (including off-road vehicles).
2) Population Management and Protection.
a) Monitor population trends through regular censuses.
b) Study life history aspects including temperature/humidity
tolerances, breeding, diseases, life span, minimum viable
population size, and foraging preferences.
c) Determine effects of environmental contaminants using surrogate
species and monitoring of forage plants, soil, ground-water, and
if necessary bioassay of snails if unusual mortality occurs.
d) Reestablish snail colonies at identified and protected suitable
sites using laboratory breeding colony or wild individuals.
3) Provide law enforcement protection to colony sites.
4) Study geologic history and past distribution of this species.
Management Practices - 4 (DRAFT) - Management Practices
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
5) Conduct information and education programs.
Management Practices - 5 (DRAFT) - References
Species SNAIL, PLEISTOCENE, IOWA
Species Id ESIS353001
Date 13 MAR 96
References
*****REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE*****
01 Frest, T.J. 1984. National Recovery Plan for the Iowa Pleistocene
Snail (Discus macclintocki (Baker)). U.S. Fish and Wildlife
Service, Twin Cities, MN. 26 pp.
02 Baker, F.C. 1928. Description of new varieties of land and
freshwater mollusks from Pleistocene deposits in Illinois. The
Nautilus 41:132-137.
03 Pilsbry, H.A. 1948. Land Mollusca of North America (North of
Mexico). Vol. 2, part 2. Acad. Nat. Sci. Phil., Monogr. 3.
04 Frest, T.J. 1981. Final report, project SE 1-4, Iowa Pleistocene
snail. Iowa St. Cons. Comm. Des Moines, IA. 162 pp.
05 Solem, A. 1976. Final reports, Contract No. 14-16-0008-965. On
file at: U.S. Dept. of Interior, U.S. Fish and Wildlife Service,
Office of Endangered Species, Washington, D.C. 6 pp.
*****REFERENCES FOR N-OCCURRENCE NARRATIVE ONLY*****
01 Frest, T.J. 1984. National Recovery Plan for the Iowa Pleistocene
Snail (Discus macclintocki (Baker)). U.S. Fish and Wildlife
Service, Twin Cities, MN. 26 pp.
References - 1