This file was created by scanning the printed publication.
Errors identified by the software have been corrected;
however, some errors may remain.
Response of Small Mammal
Communities to Silvicultural
Treatments in Eastern
Hardwood Forests of West
Virginia and Massachusetts1
Robert T. Brooks and William M. Healy2
Small mammals (i.e. New World
mice, voles and jumping mice [Cricetidae and Zapodidael, shrews [Soricidael, and squirrels [Sciuridael) are
an important component of northeastern forest ecosystems. Their positions in the f d web are broad,
iunctioning as foragers on plant and
faunal biomass and as prey to numerous predators. Small mammals
play an important role in forest dynamics by dispersing seeds and mycorrhizal fungal spores and by enhancing organic matter decomposition and mineral cycling (Spurr and
Barnes 1980).
Relatively little is known of the
response of small mammals, by species and as a community, to silvicultural treatments of northeastern
hardwood forests. Several studies
have shown that the response varies
by species but that the small mammal community is generally resilient
to forest harvesting (Healy and
Brooks 1988, Kirkland 1977, Lovejoy
1975, Clough 1987, Monthey and
Soutiere 1585).These studies report
the predominant effect of silvicultural treatments on small mammal
habitat is the enhancement of the
Paper presented af symposium, Management of Amphibians, Reptiles, and
Small Mammals in North America (Flagstaff,
AI. July 19-21, 1988).
2RobertT. Brooks and William M. Healy
are Research Wildlife Biologisk, USDA Forest
Service, Northeastern Forest Experiment
Station. University of Massachusetts,
Hd&woN Hall, Amherst, MA 0IG03.
Abstract.-We studied small mammal
communities and associated habitats in West
Virginia and Massachusetts hardwood forests with
different silvicultural treatments. In Massachusetts,
white-tailed deer (Odocoileus virginianus:)density
was a second interactivetreatment. Total capture
rates were relatively stable across all treatment
classes. Small mammal community composition and
individual species capture rates varied according to
treatment. White-tailed deer density had a greater
effect on the smal! mammal community than did
silvicultural practices.
ground cover and lesser woody
vegetation. Stenotopic species sensitive to understory plant cover and its
influence on microclimate seem to be
encouraged, at least temporarily, by
most forest harvesting, while eurytopic species seem unaffected.
The study began in West Virginia
(WV), where one field season was
completed, and was continued in
Massachusetts (MA).Our objective
was to investigate the response of the
small mammal community, as characterized by live-trapping statistics,
to standard eastern hardwood
silvicultural treatment (Marquis et al.
1975, Hibbs and Bentley 1983). In
WV, we studied the effects of evenaged regeneration clearcutting and
subsequent succession on small
mammal trapping data. In MA, the
silvicultural treatment was intermediate thinnings, with a second interactive treatment of differential whitetailed deer density.
years), and mature (>I00 years). The
12 stands averaged 19.4 ha and
ranged in area from 6.1 to 38.8 ha.
The study area is described in Healy
and Brooks (1988).
The MA study sites were on the
Quabbin Reservation in Franklin
county. This watershed is managed
by Boston's Metropolitan District
Commission for water production.
Four randomly selected stands in
each of four treatment classes were
studied to evaluate the interactive
effects of intermediate thinning and
white-tailed deer density on a southern New England oak forest's flora
and fauna. The treatments were combinations of thinned vs. unthinned
and low (6-8/mi2) vs. high (34-59/
mi2)deer density. The 16 stands averaged 19.1 ha and ranged in area
from 4.9 to 57.5 ha. The MA study
site is described in Healy et al. (1987).
METHODS
STUDY AREAS
Small Mammals
The WV study sites were on the
Cheat Ranger District, Monongahela
National Forest. Three randomly located stands in each of four standage classes were studied to evaluate
the small mammal community over a
silvicultural rotation for even-aged
management of a northern hardwood forest. The four age classes
were seedling (8-9 years), sapling
(12-14 years), sawtimber (61-76
Small mammals were live-trapped at
10 systematically located stations
along a transect in each of the 28
stands. Transects were located along
the long axis of each stand. Trap stations were no less than $0 m apart in
any stand. At each station three Sherman-type box traps (7.6 X 7.6 X 30.5
cm) were baited with a mixture of
peanut butter, rolled oats, and bacon
fat and set within 1 m of each station.
Traps were set for three successive
nights, left closed for one (WV) or
four (MA) nights, and then set for
three additional successive nights.
Sprung traps were noted and their
numbers subtracted from the total
number of trap nights per station (18)
to calculate the number of effective
trap nights. Each forest stand was
trapped once per year. Mammals
were trapped from mid-September to
early October 1981 in WV. Mammals
were trapped during June and July of
1985-87in MA. Captured mammals
were marked for individual identification and released.
Vegetation
Vegetation sampling techniques varied between states. Vegetation plots
were systematically located along the
same transects as were the small
mammal trapping stations. In WV,
trees (L 2.5 cm) were sampled using
point-centeredquarter method (Cottam and Curtis 1956), while in MA,
trees were sampled using fixed-radius plots. Herbaceous and woodystemmed understory, including trees
< 2.5 cm, were sampled in WV using
the line intercept method (Eberhardt
1978)and in MA, these flora were
sampled using fixed-radius plots.
Tree and understory sampling occurred at the same locations along
the transects. These data were used
to estimate tree density, dominance,
and average diameter and understory cover by major plant life form
(i.e. forb, fern, grarninoid, and
woody-stem species).
Analysis
Small mammal trapping results and
vegetation samples were summarized by treatment class and forest
stand. Treatment effects on small
mammal capture rates, standardized
as captures per 100 trap nights (TN),
were analyzed by one-way (WV) or
two-way (MA) analysis of variance
in a balanced, nested design with
stand sum-of-squares the error term
for treatment effect. Treatment effects on species composition of small
mammal capture rates were analyzed
using multivariate analysis of variance. Testing of treatment effects was
done using the SPSS MANOVA procedure (Hull and Nie 1981).
RESULTS
Vegetation Structure
West Virginia
Tree density declined and both basal
area and average tree diameter in-
creased as the forest stands matured
from an even-aged regeneration harvest (table 1).
The understory changed more in
life form composition than in total
cover. Forb cover increased in percentage of cover with stand-age as
did ferns while shrub cover declined
(table I). All forest stands supported
a luxuriant understory regardless of
age.
Massachusetts
Tree density and basal area decreased with thinning while average
tree diameter changed little (table 1).
The effect of deer density is understandable if one considers the low
deer-unthinned treatment to be a
"control" condition.
From this perspective, high deerdensity stands had lower tree density
and basal area, and a larger average
diameter because of poor regeneration resulting from browse damage
(table 1).
Forb cover declined with higher
deer densities, while graminoid
cover increased (table 1). Shrub and
fern cover responded irregularly to
the treatments except for a dramatic
increase in fern cover in high deerthinned stands, an effect reported
elsewhere (Marquis 1987).
Small Mammals
West Virginia
In the one trapping season, 662 individuals of 15 species were captured.
Total capture rate averaged 33.2 individuals/100 TN. Average total capture rate declined with stand-age,
from 42.4 individuals/100 TN in
seedling stands to 27.4/100 TN in
sawtimber stands, and then increased to 31.0/100 TN in mature
stands (table 2). The effect of stand-
age class on total capture rate was
not statistically significant (F = 3.16,
P = 0.086, d.f. = 3,8).
Six species were captured in all
four forest age classes, eight additional species were captured in three
or fewer treatment classes (table 2).
Species richness was greatest in the
sawtimber stands, intermediate in
the younger stands, and least in the
mature stands.
The southern red-backed vole (see
table 2 for small mammal scientific
nomenclature) was the most com-
mon species, averaging 12.7 individuals/100 TN. Capture rate for this
species declined with stand-age
through sawtimber stands (table 2),
but treatment effect was not significant (F = 2.37, P = 0.146,d.f. =3,8).
Deer mice were the second most
common species, with an average
capture rate of 10.0 individuals/ 100
TN. Capture rates for this species
were similar across treatment class
except for a lower rate in the seedling
stands. No significant differences
were found between stand-age class
(F = 0.29, P = 0.766). Short-tailed
shrews were the only other species
frequently caught in all stand-age
classes. Shrews were most common
in the seedling stands but no significant treatment effect was found (F =
0.96, P = 0.459). No significant treatment effect was found for eastern
chipmunks (F = 1.26, P = 0.351),
woodland jumping mice (F = 0.21, P
= 0.8851, and rock voles (F = 0.41, P =
0.749), which were caught infrequently in all stand-age classes (table
2). The remaining eight species were
caught with less regularity. No further analysis was completed for these
species. No significant treatment effect was found in the simultaneous
capture rates of the six most commonly trapped species (i.e., redbacked and rock voles, short-tailed
shrews, chipmunks, and deer and
jumping mice) (Wilks lambda =
0.046, Rao's F = 9.979, P = 0.54).
Massachusetts
Over 3 years, 2,630 individual small
mammals of nine species were captured. Average total capture rate was
32.6 individuals/100 TN. There was
a significant decline in capture rate
across the years (F = 30.02, P < 0.001,
d.f. = 2,241. The capture rate of 43.7
individuals/100 TN in 1985 declined
to 33.7 in 1986 and 20.3 in 1987. The
decline was observed across all treatments and all stands.
We found no significant full model
treatment effect on total capture rate
( F = 1.78,P =0.204,d.f. =3,12).Total
capture rate for all species was highest in the ranthinned stands and lowest in the thinned stands, especially
in the high deer-density stands (table
2). Neither thinning (F = 3.99, P =
0.069, d.f. = 1,12) nor deer density (F
= 0.60, P = 0.453) had a significant
effecton total capture rates.
Species richness was highest in the
high deer-thinned treatment class,
intermediate in the two low deerdensity classes, and lowest in the
high deer-unthinned treatment (table
1). White-footed mouse was the most
commonly captured species, followed by southern red-backed voles
(table 2). Capture rates for both species differed by treatment class (F =
9.01, P = 0.002, d.f. = 3,12 for mice; F
= 6.06, P = 0.009 for voles), with deer
density a significant effect (F = 20.7,
P = 0.0007. d.f. = 1.12 for mice; F =
17.5, P = 0.01 for voles), and thinning
effect nonsignificant (F = 2.72, P =
0.125 for mice; F = 0.11, P = 0.74 for
voles). Voles were most commonly
captured in stands of low deer-density, and mice most commonly captured in stands of high deer-density.
Short-tailed shrews and eastern
chipmunks were the only other species captured in each of the dour
treatments. Shrew captures, like
those for red-backed voles, declined
with increasing deer density (F = 6.2,
P = 0.028) but showed no significant
response to thinning (F = 3.1, P =
0.1). Chipmunk captures showed no
significant response to either deer
density (F = 0.95, F = 0.35) or thinning (F = 1.52, P = 0.24). The remaining five species were infrequently
caught in three or fewer treatment
classes, and no further analysis was
performed.
Relative capture abundance of the
four most commonly captured species (i.e., white-footed mice, redbacked voles, short-tailed shrews,
and chipmunks) differed between the
two levels of deer density (Wilks
lambda = 0.237, Rao's F = 7.25, P =
0.007). No difference in relative capture abundance was found between
the two thinning classes (Wilks larnbda = 0.496, Rao's F = 2.28, P = 0.14).
Silvicultural treatments had no significant effect on total small mammal
captures. Total capture rates were
stable across the range of treatments
in both WV (clear-cutting and subsequent regrowth) and MA (intermediate thinning) with the exception of
WV seedling stands (table 2). In
those stands, where regenerating
trees, shrubs, and herbaceous plants
flourish in the sunlight afforded by
the removal of the overstory, total
capture rates increased. Otherwise,
treatment effects on habitat structure
were insufficient to alter total capture rates, as changes in the species
composition of small mammal captures were compensatory.
Six of the 14 small mammal species captured in WV were captured
in all four stand-age classes. Of the
other species: red squirrels were observed in all stands but poorly captured in our traps; white-footed
mice, woodland and meadow voles,
and masked and long-tailed shrews
were each captured in one stand;
four smoky shrews were captured in
three stands; and southern flying
squirrels were captured in sapling
and older stands. McKeever (1955)
generally concurs that these species
are uncommon in WV (woodland
vole, masked and long-'tailed shrew),
or are common in forests not
sampled in this study (white-footed
mouse in lower elevation forests) or
other habitats (meadow vole). Smoky
shrews and southern flying squirrels
are more common WV srnall mammals but were poorly represented in
our sample. Capture data for 'these
species are insufficient for drawing
any conclusions regarding species
response to clearcutting.
West Virginia red-backed vole and
short-tailed shrew captures increased
concurrent with a decline in deer
mouse captures (table 2). Vole and
shrew capture rates were highest in
seedling stands. Kirkland (1977) and
Lovejoy (1975) reported a similar response in vole captures but not for
shrew captures. The increase in vole
captures could be a response to the
flush in vegetation associated with
overstory removal and to the volume
of slash occurring immediately subsequent to harvest. These factors alter ground level microclimate, increasing humidity and improving
conditions for red-backed voles
(Lovejoy 1975, Merrit 1981).
Vole and shrew captures declined
and deer mice captures increased as
the forest stands matured. Forb cover
remained stable with increasing
stand-age while fern cover increased
and shrub cover declined (table 1).
These changes presumably altered
microhabitat conditions to the detriment of red-backed voles. In mature
forest stands, vole and mouse captures were equal. In these stands,
forb cover increased dramatically
from conditions observed in sawtimber stands, fern cover declined, and
shrub cover remained stable (table 1).
These habitat conditions resulted in
an increase in red-backed vole captures in mature stands over capture
rates for the species in sawtimber
stands.
Less frequently trapped rock voles
were captured in stands with rock
outcrops. Eastern chipmunks captures increased with stand age, and
woodland jumping mice captures
showed no clear response to stand
age. Capture rates for these two species were not related to measured
habitat variables (Healy and Brooks
1988).
Species composition of WV small
mammal captures and individual
species capture rates were not significantly different between treatment
classes. No major small mammal species was eliminated by clearcutting
and the subsequent maturing of the
regeneration of the hardwood
stands. These species either survived
within clearcut stands or recolonized
harvested stands from adjacent uncut stands. Within maturing stands,
habitat conditions were sufficiently
diverse to support all major species.
These results demonstrate that
clearcutting of WV northern hardwood forests allowed for the continued maintenance of the small mammal community. Our data showed
the small mammal community to be
relatively stable across a silvicultural
rotation, with no major changes in
composition or capture rates that
could alter forest ecosystem functioning or character.
Total capture rates were stable
across treatment classes in MA.
Treatment effects upon habitat structure in these stands were insufficient
to alter total capture rates. However,
capture rates for individual small
mammal species varied among forest
treatments. Deer-density had a
greater influence on both individual
species capture rates and species
composition than did silvicultural
treatment. There was a reciprocal
change in the relative abundance of
red-backed voles and white-footed
mice with changes in deer density
(table 2).
During the 3 years of this study,
fall deer density averaged 18/km2 in
the high deer-density stands and 3/
km2 in the low deer-density stands
(Healy et al. 1987).Red-backed voles
were scarce in high deer-density
stands. Ferns and ericaceous shrubs
dominated the understory of these
stands while the understory of low
deer-density stands contained a
greater overall number of plant species and forb species were more
abundant (Healy et al. 1987).Redbacked voles prefer mesic to hydric
sites, especially in the southern portion of their New England range
(Miller and Getz 1972,1973).It seems
that foraging by deer may have sufficiently altered the understory vegetation to depress vole populations.
The response of white-footed mice
to deer density in MA was less clear.
Although capture rates in low deerdensity stands were fewer than in
high deer-density stands, they nevertheless exceeded capture rates for
red-backed voles in all treatment
classes (table 2). White-footed mice
are ubiquitous in habitat preference
within the forest ecosystem (King
1968, Godin 1977, Hamilton and
Whitaker 1979). Whereas Wolff and
Dueser (1986) suggest that the these
two species can coexist noncompetitively through microhabitat and food
habit differences, our data suggest
that mice capture rates are suppressed in stands with high vole capture rates. Our stand data are at too
coarse a scale to address microhabitat separation. One would need to
manipulate vole populations experimentally to evaluate whether the
abundance of voles is competitively
suppressing mice populations in low
deer-density stands with better quality vole habitat.
Short-tailed shrews captures were
more common in low deer-density
stands, a possible response to the
greater forb cover observed in these
stands and probable increase in
ground level humidity. Eastern chipmunk captures offer no ready interpreta tion in regard to response to
treatment effect or habitat structure.
The remaining five species were captured so infrequently that it is impossible to draw any conclusions as to
the effects of either thinning or deer
density on capture rates.
Thinning MA oak forests had no
significant effect on capture rates of
the four major small mammal species
or species composition of the captures. From a management perspective, intermediate thinning of these
forests did not alter the continuation
of the pretreatment small mammal
community. For those situations
where white-tailed deer have been
allowed to reach population levels
where vegetation is altered, significant changes in the small mammal
community are found. Silvicultural
treatment effects on small mammal
habitat are temporary and ecosystem
resources (i.e. nutrients, energy) remain available to small mammals.
Long-term, high populations of deer,
a large, possibly competing herbivore, alter the structure and composition of small mammal habitat to the
detriment of some species.
CONCLUSIONS
The small mammal community is an
important component of northeastern forested ecosystems, functioning
both as a consumer of plant and animal biomass and as prey to numerous predators. Intermediate thinning
and clearcutting treatments, which
are common silvicultural practices,
have minimal or ephemeral effects
on the numbers of small mammals
and the composition of the small
mammal community found in these
forests. Long-term, high deer populations may permanently alter habitat
structure to the extent that changes
occur in small mammal community
composition.
LITERATURE CITED
Clough, Garrett C. 1987. Relations of
small mammals to forest management in northern Maine. Canadian
Field-Naturalist 101:40-48.
Cottam, Grant and J. T. Curtis. 1956.
The use of distance measures in
phytosociological sampling. Ecology 37:451-460.
Eberhardt, L. L. 1978. Transect methods for population studies. Journal
of Wildlife Management 42:l3l.
Godin, Alfred J. 1977. Wild mammals
of New England. 304 p. The John
Hopkins Press, Baltimore, Md.
Hamilton, William J. and John 0.
Whitaker. 1979. Mammals of the
eastern United States. 346 p. Cornell University Press, Ithaca, N.Y.
Healy, William M. and Robert T.
Brooks. 1988. Small mammal
abundance in northern hardwood
stands of different ages in West
Virginia. Journal of Wildlife Management 52(3):[in press].
Healy, William M., Robert T. Brooks,
and Paul J. Lyons. 1987. Deer and
forests on Boston's municipal watershed after 50 years as a wildlife
sanctuary. p. 3-21. In Deer, forestry, and agriculture: Interactions
and strategies for management.
David Marquis, editor. Syrnposium Proceedings, Plateau and
Northern Hardwood Chapter, Allegheny Society American Foresters, Warren, Pa.
Hibbs, David E. and William R.
Bentley. 1983. A Management
Guide for Oak in New England. 12
p. The University of Connecticut,
Cooperative Extension Service,
Storrs.
Hull, C. Hadlai and Norman H. Nie.
1981. SPSS Update 7-9: New procedures and facilities for releases
7-9.402 p. McGraw-Hill Book
Company, NY.
Jones, J. Knox, Dilford C. Carter, and
Hugh H. Genoways. 1975. Revised
checklist of North American mammals north of Mexico. 14 p. The
Museum, Texas Tech. Univ., Lubbock. Occasional Paper No. 28.
King, John A. 1968. Biology of Peromyscus (Rodentia). 593 p. The
American Society of Mammalogists. Special Publication No. 2.
Kirkland, Gordon L. 1977. Responses
of small mammals to the clearcutting of northern Appalachian forests. Journal of Mammalogy
58:6Oo-609.
Lovejoy, David A. 1975. The effect of
logging on small mammal populations in New England northern
hardwoods. University of Connecticut Occasional Papers, Biological Science Series 2:269-287.
Marquis, David A., editor. 1987.
Deer, forestry, and agriculture:
Interactions and strategies for
management. 183 p. Symposium
Proceedings, Plateau and Northern H a r d w d Chapter, Allegheny Society American Foresters. Warren, Pa.
Marquis, David A., Ted J. Grisez,
John C. Bjorkbom, and Benjamin
A. Roach. 1975. Interim Guide to
Regeneration of Allegheny Hardwoods. USDA Forest Service General Technical Report NE-19.14 p.
Northeastern Forest Experiment
Station, Broomall, PA.
McKeever, Sturgis. 1955. Ecology
and distribution of the mammals
of West Virginia. Ph.D. Dissertation. 335 p. North Carolina State
College, Raleigh.
Merrit, Joseph F. 1981. Clethrionomys
gapperi. 9 p. The American Society
Mammalogists Mammalian Species No. 146.
Miller, Donald H. and Lowell L.
Getz. 1972. Factors influencing the
local distribution of the redback
vole, Clethrionomys gapperi, in New
England. University of Connecticut Occasional Papers, Biological
Science Series 2:115-138.
Miller, Donald H. and Lowell L.
Getz. 1973. Factors influencing the
local distribution of the redback
vole, Clethrionornys gapperi, in New
England. 11. Vegetation cover, soil
moisture, and debris cover. University of Connecticut Occasional
Papers, Biological Science Series
2:159-180.
Monthey, Roger W. and E. C. Soutiere. 1985. Responses of small
mammals to forest harvesting in
northern Maine. Canadian FieldNaturalist 99:13-18.
Spurr, Stephen H. and Burton V. Barnes. 1980. Forest Ecology. 687 p.
3rd edition. John Wiley and Sons,
N.Y.
Wolff, Jerry 0. and Raymond D.
Dueser. 1986. Noncompetitive coexistence between Peromyscus species and Clethrionomys gapperi. Canadian Field-Naturalist 100:186191.