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SOME EFFECTS OF DEER BROWSING
ON NORTHERN MICHIGAN FOREST

PLANTS

By
JERRY PAUL DUVEI’JDECK

A THESIS
Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE
Department of Zoology

1952

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2

SOME EFFECTS OF DEER BRONSING ON NORTHERN

MICHIGAN FOREST PLANTS

According to Bartlett (1950), Michigan has a herd of appro-
ximately 1,000,000 whitetail deer (Odocoileus virginianus borea-
112), and he estimates that 600,000 of these are in the northern
portion of the Lower Peninsula. He believes that the herd reach-
ed this peak in 1939 and that it has fluctuated thereabouts
since.

As early as 1930 Bartlett found that portions of this part
of Michigan were overpopulated with deer, and by 1936 winter
starvation was common in these areas. His records indicate
that the overpOpulated, or starvation, areas have continually
eXpanded until they now cover the area shown in Figure 1.

In order to study and evaluate the damage that deer do to
forest plants and their reproduction, the Game Division of the
Michigan Conservation Department built 16 deer exclosures.

These exclosures are one acre or less in size, surrounded by an
eight foot fence designed to exclude deer. Six were completed
in 1937, and 10 in January 1950. During the summer of 1950

the vegetation of these exclosures and of nearby unfenced con-
trol areas were studied in an effort to determine the effect of

deer browsing in these areas.

Methods
The designations, sizes, locations, and year of construc-

tion for each exclosure studied are listed in Table 1. Their

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TABLE 1

DEER EXCLOSURES IN THE NORTHERN PORTION OF THE LOWER
PENINSULA OF MICHIGAN, THEIR DESIGNATION, SIZE,

LOCATION AND DATE ESTABLISHED

 

 

 

 

Date———-

Designa- Size in Location Estab-

tion acre§_ County; Subd. Sec. TN R _1ished

A 1 Lake 8% SE% 4 18 12W 1937
B 1 " 8% SE% 4 18 12w "
c 1 " 8% 33% 4 18 12w "
D l " N% NE} 9 18 12w "
E l " N% NE% 9 18 12W "
F .25 Crawford SE% SW% 16 26 4T "

l .5 Presque Nwi SW% 27 34 SE 1950

Isle

2 1 Montmorency SW% SE% 15 29 3E "
3 .1 Ogemaw swi NE% 2 23 3E "
4 .05 ” NW% SE% 6 23 1E "
5 1 Roscommon SW% NW% 20 24 4W "
6 .5 " SW% 88% 34 24 4W "
7 1 Manistee NE% SE% 30 24 13W "
8 1 Lake swfi NW% 10 13 12w "
9 .05 Gladwin SW% NW% 10 20 2W "
10 1 " NWi SW% 10 20 2W "

 

locations in relation to the starvation area is shown in Fig-
ure 1.

For each exclosure an unfenced control area was staked out.
The controls were established parallel to one side of the ex-
closures where the same major vegetation types present in the
exclosures were found, and placed 6.6 feet away from the exclo-
sures to eliminate the deer runways that were frequently found
along the exclosure fences. Thus each exclosure and its control
presented a comparison between an area available to deer and a
similar area not available.

A standard procedure was used in examining all exclosures
and control areas. Equally spaced transects 6.6 feet wide were
established parallel to the ends of the areas. These sample
strips comprised 10 per cent of the area in the exclosures and
in control areas one-half acre or larger. They included 20 per
cent of smaller plots. The entire plots of exclosure 4 and its
control were studied. Permanent cedar stakes protruding three
feet above the ground were placed at the ends of all of the
sampled transects. Each stem of woody vegetation found in the
sample strips was tallied on a standard form by species, sizes
class, and percentage of available browse remaining on the stem.
Species, when unknown, were determined from Fernald (1950).

Size was determined by actual measurement, and seven size classes
were used. Available browse was considered to be leaves, buds,
fruits, and live twigs up to one-quarter inch in diameter found

between ground level and eight feet in height. The percentage

of available browse remaining was determined by a mental com-
parison of each stem with the probable normal stem of the same
Species growing without competition or damage. Four percentage

classes were used. They were:

1. Browsed out: No available browse remaining.

2. Heavily browsed: l - 33 per cent remaining.

3. Moderately browsed: 34 - 66 per cent remaining.

4. Lightly or not al all browsed: 67 - 100 per cent
remaining.

General notes were taken on herbaceous vegetation and its appar-
ent effect on tree reproduction.

In analyzing the data collected the chi-square test was used
frequently to determine whether differences were statistically
significant. In this paper if the test indicated differences
significant at the five per cent level the word “significant“
has been used, and if the test found differences significant at
the one per cent level the words "highly significant" have been

used. -

Acknowledgments

I take pleasure in acknowledging the generous c00peration
and help of the following agencies and individuals. First I am
indebted to the Game Division of Michigan's Conservation Depart-
ment for assigning the study to me. Ben C. Jenkins contributed
time and guidance in collecting data in the field. Ford Kellum
contributed his knowledge concerning deer food preferences in
compiling Table 2. William Laycock, Philip Baumgras, John Bye-

lich, and Otto Failing, District Game Supervisors, aided with

advice and knowledge concerning individual exclosures in their

districts. Dr. George A. Petrides assisted in editing the paper.

Findings

For convenience in reporting, the various woody species
found in this study are classified (Table 2) according to their
probable palatability to deer. This list, compiled by Ford
Kellum and myself, is supported in part by Maynard, Bump, Darrow,
and Woodward (1935), Davenport (1939), Petrides (1941), Man-
ville (1947), and Swift (1948, 1950). The list indicates the
probable order in which deer would choose the plants as food,
and is not a list designating the value of these Species from

a nutritional standpoint.

Exclosures Built in 1937

The exclosures built in 1937 are all in deeryard swamps
that had been heavily overbrowsed prior to construction of the
exclosures. Five (A - E) are in the Luther Baldwin Swamp in
Lake county and the sixth (F) is in the Bear Creek Swamp in
Crawford county.

Exclosures A - E. During the winter of 1935-36 the Luther
Baldwin Swamp was cut in a ”checkerboard" pattern. Alternate
two and one-half acre plots were cut over. The Openings materi-
ally affected the resulting plant communities in and around the
cut over areas. Before they were cut the dominant species were
balsam fir, white cedar, red and silver maple, black ash, balm

of Gilead, basswood, slippery elm, and aspen (Michigan Depart-

TABLE 2

PROBABLE ORDER CF PALATABILITY IN NORTHERN
MICHIGAN WOODY PLANTS FOUND

Preferred

1.

American yew

White cedar

Red-osier dogwood
Alternate-leaved dogwood
Staghorn sumac

Eastern hemlock
Mountain-ash

Red maple

Black ash

Juneberries

Second Choice

 

11. Witchhazel

12. Silver maple

l3. Hazelnut

14. Ninebark

15. Wild raisin

16. Aspen

17. White oak

18. Nannyberry

l9. Bush-honeysuckle
20. ‘Winterberry

21. Swamp fly honeysuckle
22. White birch

23. Basswood

24. WIIIOWS

25. Jack pine

26. American fly honeysuckle
Starvation

27. Balsam fir

28. Balm of Gilead
29. Northern red oak
30. Black cherry

31. Tamarack

32. Red pine

33. White ash

34. Pin cherry

35. Choke cherry

36. Slippery elm

37. Sheep laurel

38. Swamp birch

39. Speckled alder
40. Black spruce

Taxus canadensis
Thuja occidentali£_
Cornus stolonifera
Cornus alternifolia
Rhus typhina

Tsuga canadensig
Pyrus americana
Acer rubrum
Fraxinus nigra
Amelanchier spp.

 

Hanam3113~virginiana
Acer saccharingg.
Corylus spp.
Physocarpugvopulifolius
Viburnum cassinoides
Populus tremuloidgg
Quercus alba

Viburnum Lentagg
Diervilla Lonicera
Ilgx verticillata
Lonicera oblongifolia
Betula_papyrifera
Tilia americana

Salix spp.

Pinus Banksiana
Lonicera canadensig

Abies balsamea
Populus balsamifera
Quercus rubra var. borealis
Prunus serotina
Larix laricina
Pinus resinosa
Fraxinus americana
Prunus pensylvanica
Prunus virginiana
Ulmus fulva

Kalmia angustifolia
Betula pumila
Alnus rugosa

Picea mariana

 

ment of Conservation, Game Division, unpublished). Balsam fir
and white cedar had not become reestablished in these areas at
the time of the study. Deciduous species now make up the domi-
nant forest cover. The five exclosures were built so that half
of each was in a cutover area and each remaining half was in an
uncut plot.

Plantings of red-osier dogwood, white ash, and basswood
were made in the fall of 1936 in three of the cut over areas
where exclosures were later placed. They were made, however,
before the exclosures were built and thus were subject to brow-
sing throughout before parts of them were fenced. The species
composition of all exclosures, planted or not, was statistically
similar.

Table 3 lists all the preferred deer foods found in these
exclosures and controls and the percentages of each in the four
classes of available browse.

American yew was found in the parts of the exclosures where
no cuttings had been made. It did not occur in the control areas.

White cedar was present in both exclosures and controls,
but only 5.1 per cent in the contrOls had available browse While
31.7 per cent of the stems in the exclosures had available browse
remaining. No new white cedar stems in either area had grown
beyond the height of two feet, but half of the new stems in the
exclosures were between one and two feet tall while all of those

in the control area were seedlings less than three inches high.

TABLE 3

PERCENTAGES OF TOTAL NUMBER OF STEMS OF PREFERRED ERCASE
PLANTS IN THE FOUR CLASSES 0F AVAILABLE ERONSE PRESENT
IN 1950 IN EXCLOSURES AND CONTROLS A, B, c, D, E
LAKE COUNTY, MICHIGAN CONSTRUCTED IN 1937

 

 

 

 

 

 

 

 

 

 

Species Total Percentage of available browse remaining
number
of stems
found 0 l - 33 34 - 66 67 - 100
American 46 E* 100
yew
0 C**
white cedar 139 E 68.3 10.8 20.9
_;136 C 94.9 0.7 4.4
dogwood
426 C _12.0 40.1 47.9
Alternate- 78 E 3.8 35.9 60.3
leaved
dogwood _51, C 22.0 34.1 43.9
Hemlock 23 E 34.8 13.0 52.2
17 C 100
mountain- 148 E 7.4 61.5 3101
ash
89 C 25.8 70.8 3.4
Red maple 332 E 7.8 7.2 15.4 69.6
253 C 11.5 16.6 5.9 66.0
Black ash 327 E 18.7 26.3 33.0 22.0
410 C 28.7 52.7 12.7 5.9

 

* - Exclosure

%* - Control

- 10 -

Trees that had been heavily browsed before the exclosures were
built showed some browse regeneration within the exclosures
but none outside.

Hemlock presented an even greater contrast with no avail-
able browse in the control areas and 65.2 per cent in the ex-
closures with available browse remaining.

The five other Species of preferred deer foods listed in
Table 3 also showed highly Significant greater availability of
browse in exclosures.

Aspen, silver maple, American and swamp fly honeysuckle,
white birch, basswood, and willow were second choice deer foods
found in these five exclosures and their control areas.

Most of the aSpen stems (73 per cent) in both exclosures
and controls were of the same size (about three inches DBH),
and the majority of these were in areas that had been cut over.
This would indicate that this species had reproduced well in
the cut over areas for a few years and then had been unable to
continue as other vegetation matured. The differences in total
number of stems of this species found inside (117) and outside
(70) the exclosures was highly significant. Deer had evidently
reduced aSpen reproduction in the control area. The amount of
browse available on aSpen stems in the exclosures was not sig-
nificantly more than the amount per stem in the control areas.

These data indicate that as aSpen became mature self-pruning

eliminated most low browse.

-11-

There were 11 times as many stems of American fly honey-
suckle and over twice as many stems of swamp fly honeysuckle,
basswood, and silver maple in the exclosures as there were in
the controls. These differences all were statistically highly
significant. The amounts of available browse on these Species
and on willow inside the exclosures was significantly more than
outside in the control areas.

There were 76 stems of white birch under eight feet in
height in the exclosure, and 47 of the same class in the con-
trols. The difference in number of stems, and a greater amount
of available browse on the stems in the exclosures were both
found to be highly significant. The other larger stems of this
Species in both areas had little browse left available to deer.

Balsam fir was the only starvation food species in these
areas that deer had used to a point where a definite difference
could be Shown. There were about four times as many stems of
balsam fir as there were of balm of Gilead, red oak, black,
choke and pin cherry, white ash, and slippery elm. This greater
availability may indicate why it has been heavily browsed after
more palatable foods were consumed. The greater amount of
available browse per stem on the balsam fir in the exclosures,
as well as the difference in numbers of stems, was highly sig-
nificant.

Speckled alder was as abundant as balsam fir but it had not
been heavily browsed. This would tend to confirm the placement

of speckled alder near the bottom of the palatability list.

- 12 -

In those parts of the swamp that had been cut over, her-
baceous ground cover was heavier than in the uncut portions.
Currants (filb§§_spp.), raspberries (figbg§_spp.), and Spotted
jewelweed (Impatiens capensis) were common in the cut over
areas. Ground dogwood (Cornus canadensis), currents (31223;
spp.), and various ferns were found in the uncut portions.

This ground cover was apparently not inhibiting forest repro-
duction.

Exclosure F and its control, None of the area of exclosure
F or its control had been cut over so it was considered separate-
ly from exclosures A - E.

Fifteen woody Species were found in exclosure F, and eight
were found in the control area. Table 4 lists these species and
their abundance. The per cent of stems in browse percentage
classes was not included in a table because of the small numbers
of stems involved. Seven Species were present in the exclosure
and not in the control. Two were preferred foods, and five were
second choice. The difference in number of Species found in the
two areas is significant Just above the five per cent level.

There was no available browse on white cedar stems in the
control area. Significantly, 10 of the 16 stems in the exclosure

had available browse. Four small white cedar stems in the ex-
closure indicated that reproduction was taking place. None was

found outside.

All 29 stems of red maple found in the control area were

£3eedlings less than four inches in height. In the exclosure,

- 13 -

TABLE 4

SPECIES FOUND IN EXCLOSURE F, BUILT IN 1937, AND ITS

CONTROL AREA CRAWFORD COUNTY, MICHIGAN

Species

Red maple

Sheep laurel
Balsam fir

Black spruce
Speckled alder
Red-osier dogwood
Swamp fly honeysuckle
White cedar
Ninebark

White birch
Winterberry
Juneberry

Aspen

Black ash

Red oak

Numbers of stems

Exclosure
65
63
42
39.
34
25
19
16

{0100103

H

Control

29
25
4
31'
113
31

- 14 -

30 of the 65 stems found were seedlings and the remaining stems
ranged in height up to five feet. In the absence of deer, both
white cedar and red maple apparently can reestablish themselves
in this region, while in the area available to deer they had
not been able to successfully reproduce.

Red-osier dogwood was not heavily browsed in the area. No
statistical difference between protected and unprotected plots
could be shown. All stems seen were under two feet tall.

No balsam fir reproduction and no available browse on the
stems of this species were found in the control area. In the
exclosure, 86 per cent of the balsam fir stems were under two
feet tall and 75 per cent of the remaining stems had up to 33
per cent browse remaining. The differences were highly signi-
ficant. Spruce stems under eight feet tall were browsed in the
unprotected area. Little new growth was noted there, while
small spruces within the fence had grown as much as six inches
in the previous growing season.

Sphagnum moss covered much of the ground in this exclosure
and its control. Ground dogwood (Cornus canadensis), showy lady-
slippers (Orchis Spectabilis), and various ferns were common.

Forest reproduction was apparently not hindered by ground cover.

Exclosures Built in 1950
The exclosures built in 1950 were located in three general
areas with respect to deer damage: (1) areas not damaged by

deer; characterized by no browse line and little evidence of deer

- 15 -

crepping on any forest Species; (2) areas moderately browsed;
where the preferred deer food Species had been moderately to
heavily browsed, but usually with no definite browse line; and
(3) overbrowsed areas with a definite browse line.

Areas not damaged by deer. Exclosures l in Presque Isle
county and 7 in Manistee county were in swamps that deer had
not damaged. Yew was present in similar numbers in exclosure
7 and its control. Red maple, juneberries, alternate-leaved
dogwood, mountain-ash, and black ash were other preferred deer
food Species found there. Cedar and red-osier dogwood were
common throughout exclosures l and 7 and their controls.

Most of the white cedar stems in these areas had available
browse from the ground to the eight foot level. In one area
of exclosure 7 and its control where forest cover was heavy,
self-pruning had reduced the potential amount of available
browse on the lower stems. 0f the 229 white cedar stems found
in exclosure 7 and its control, 15.7 per cent had been self-
pruned to a point where no available browse remained, and an
additional 16.6 per cent had less than 33 per cent available
browse remaining. There were no white cedar stems in exclosure
1 and its control with less than 34 per cent available browse
remaining. The second choice and starvation food Species in
both exclosures were similar in condition. Deer had not affected

them. Ground cover in the two areas did not seem to be affect-

ing forest reproduction.

- 15 -

Areas moderately browsed. Exclosures 5 and 6 in the Dead
Stream Swamp in Roscommon county displayed no browse line.

White cedar, red-osier dogwood, red maple, black ash, june-
berry, and hemlock were preferred Species present there. All
had been browsed but no statistical differences occurred between
exclosures and controls. When the white cedar stems of exclo-
sures and control areas 1 and 7, in areas of low deer numbers,
were compared with white cedar in exclosures and control areas
5 and 6 where deer are more numerous, the following highly sig-
nificant differences were found which indicate the differences
which characterize the two deer range types:

‘ Percentages of stems
Total no. Browsed Heavily Moderately Lightly

 

 

of stems out browsed browsed browsed
Exclosures
l & 7 and 418 8.6 9.1 28.9 53.3
controls
Exclosures
5 & 6 and 319 35.1 18.8 21.0 25.1
controls

Deer had apparently reduced considerably the amounts of available
browse in the areas of exclosures 5 and 6 and their controls.
Other preferred food Species in this area that had been similar-
ly reduced in amounts of available browse were red-osier dogwood,
red maple, and Juneberry. Black ash and hemlock were not present
in exclosures l and 7 and their controls.

Among second choice deer food Species, winterberry, willow,
swamp fly honeysuckle, wild raisin, white birch, hazelnut,
witchhazel, and aSpen were present in exclosures 5 and 6 and

their controls. Deer had not browsed any of these Species

 

N-
‘III
III]

.61

- 17 -

heavily. The ground cover in these areas was not apparently
inhibiting forest reproduction.

Overbrowsed areas. Exclosures 2, 3, 4, 8, 9, and 10 were
built in 1950 in areas that had been overbrowsed by deer. There
was a definite browse line in or near each of the exclosures.
Each of the exclosures was different from the others.

Exclosure 2 was in Montmorency county for ten years on the
edge of the starvation area. White cedar and balsam fir com-
prised 62.2 per cent of the total number of stems in the exclo-
sure, and 63.9 per cent of those in the control area. Both
species had been heavily browsed by deer. 0f the white cedar
stems in the control only two per cent had available browse
remaining while 24.2 per cent of the stems in the exclosure
possessed suitable foliage. This difference is highly signifi-
cant. It had apparently occurred in the previous six months.

Sixteen stems of American yew were found in the exclosure
and three were present in the control area. The stems in the
exclosure had been browsed before the exclosure was built, but
in the past growing season they had produced new growth. The
three stems of yew in the control area were heavily browsed and
no new growth was found.

There were a few red maple stems over eight feet in height
scattered through the areas, but none of these larger stems had
available browse. There were 64 stems under five feet tall in
the exclosure, and only seven in the control. These differences

were highly Significant. Red-osier dogwood was more abundant

- 18 -

in the exclosure than in the control area and alternate-leaved
dogwood was absent in the control.

The second choice deer food Species, white birch, swamp
fly honeysuckle, aSpen, and willow, were all twice as abundant
in the exclosure as in the control. The greater amount of
browse per stem on white birch stems was highly Significant.

Balsam fir, though heavily browsed, was not significantly
different in amount of browse available per stem between the
exclosure and its control. The other starvation food species
found had not been much browsed by deer.

Exclosure 3 and its control area, in the Rifle River State
Game Area in 0gemaw county, were clearcut of all woody vegeta-
tion Just prior to construction. Balsam fir and white cedar
were the dominant forest Species in the surrounding swamp.
There was a definite browse line in this swamp.

Eight woody Species were found in the exclosure and six
were found in the control area. A total of 209 stems were
counted in the sampled portion of the exclosure while only 61
stems were counted in the sampled part of the control. This
difference in total number of stems is highly significant, and

is tabulated by Species as follows:

 

Exclosure Control
Red-osier dogwood 92 8
Black ash 89 29
Speckled alder 8 ~-
Red maple 6 2
Balsam fir 5 l7
Winterberry 5 --
Red oak 3 1
Black spruce l --

4

White birch -

- 19 -

All of the stems found inside the exclosure had more than
67 per cent browse remaining. Only 43 per cent of the stems in
the control area were in this category. 0f the other stems in
the control area, 44 per cent were moderately browsed and 13 per
cent were heavily browsed.

None of the stems in either area had grown beyond five
feet tall. In the exclosure 56 per cent of the stems and in
the control only 15 per cent of the stems were over two feet
tall. The difference is highly significant. Black ash and red-
osier dogwood were the species that contributed most to the
difference.

The stems present in the area had developed as reproduction
in the six months since the area had been clearcut. Deer had
apparently reduced this reproduction in the control area to one
third of that found in the exclosure. Ground cover was not in-
hibiting forest reproduction.

Exclosure 4 was on the 0gemaw State Game Refuge. The semi-
tame deer herd here had overbrowsed the area. Jack pine was the
only Species found in the exclosure and its control area. Four-
teen stems were found in the.exclosure and nine in the control
area. Two additional dead stems in the control area apparently
had been recently killed by overbrowsing. New growth was noted
on all of the stems in the exclosure, and none was found in the
control area. The grass sod that formed the ground cover un-

doubtedly was a contributing factor in limiting reproduction.

- 20 -

Exclosure 8 was near the edge of the Luther Baldwin Swamp
which had been in the starvation area for 15 years.

Twenty-eight stems of red maple and eight of juneberry were
the only stems of preferred deer food found in the area. All
of these had been browsed, but there was no significant differ-
ence between the exclosure and its control.

Bush-honeysuckle, aSpen, witchhazel, white oak, willow,
hazelnut, and white birch were second choice food species found.
Bush-honeysuckle was not heavily browsed. Young aspen stems in
both areas had been moderately browsed. Witchhazel, hazelnut,
and white birch also had been browsed, but not in the past six
months to where significant differences could be shown between
fenced and unfenced areas.

0f the white oak stems under eight feet in height found in
the exclosure, 82.9 per cent had more than 67 per cent available
browse remaining. The other similar oak stems in the exclosure
had between 34 and 66 per cent available browse remaining. In
the control 57.8 per cent of the similar white oak stems had been
lightly browsed, 33.3 per cent moderately browsed, and 8.9 per
cent heavily browsed. The greater browsing of the control was
statistically significant. It had apparently occurred in the
past six months. Unfenced jack pine had been browsed heavily
in this area, but new growth up to eight inches long prevailed

on the stems in the exclosure. Starvation food species had not

been much browsed.

-21-

Forest reproduction did not seem to be inhibited by the
ground cover of bracken (Pteridium sp.), strawberry (Fragaria sp.),
a few grasses and other herbs.

Exclosure 9 was in the Gladwin State Game Refuge. The area
had been overbrowsed by deer. Sumac was the only woody species
in the exclosure and its control area. The greater amount of
available browse per stem found in the exclosure was highly sig-
nificant. Reproduction was apparently as good in the control
as it was in the exclosure. Sweet fern (Comptonia peregglgg.,
milkweed (Asclepias sp.), and grasses made up the ground cover.
It did not seem to be affecting reproduction of other woody
plants.

Exclosure 10 also was located in the Gladwin Refuge. Red
maple, red-osier dogwood, white cedar, and black ash were the
preferred deer food Species present. Only two of the 112 white
cedar stems in the exclosure and control had available browse,
offering no basis for measurement. The amount of available
browse per stem on red maple stems in the exclosure was enough
greater to be significant. Red-osier dogwood had been browsed
in both exclosure and control. Little available browse was left
on the stems of black ash present in both areas. White birch,
Willow, aSpen, hazelnut, jack pine, and basswood were second
choice food species found. All had been browsed, but no signi-

ficant differences could be shown between the exclosure and its

control.

Balsam fir had been heavily browsed before the exclosure
was built. There was no available browse on any of the stems
over eight feet in height, and the only smaller balsam fir stems
found were seedlings. The other starvation foods had not been
heavily browsed in this area.

In parts of the exclosure and control, grasses had formed

a heavy sod, andin these areas forest reproduction was lacking.

Conclusions

1. American yew has been almost extirpated by deer in over-
browsed areas.

2. White cedar and hemlock have become so heavily browsed
as to produce little available browse through growth and re-
generation. Little or no successful reproduction of these
species occurred in overbrowsed areas.

3. Amounts of available browse on red-osier dogwood, al-
ternate-leaved dogwood, sumac, mountain-ash, red maple, and
black ash were usually highly significantly reduced in overbrow-
sed areas, and reproduction on these deciduous preferred Species
more often than not was significantly reduced.

4. In six months in some overbrowsed areas, deer signifi-
cantly reduced the amount of available browse on such preferred
deer food species as American yew, white cedar, and red maple.

5. In clearcut areas, deer reduced forest reproduction to

one third of that prevailing in exclosures.

-23-

6. In previously overbrowsed areas, coniferous deer food
plants did not produce any stems over two feet in height in 13
years, even when protected from deer.

7. Even in moderately browsed areas deer significantly re-
duced available browse on white cedar and other preferred deer
food Species. Second choice and starvation foods were not much
damaged.

8. Self-pruning in one area of heavy forest cover signifi-

cantly reduced the amount of available browse on white cedar.

Summary

The woody vegetation of 16 deer exclosures and of browsed
but otherwise comparable nearby control areas were studied be-
tween June and October 1950 in the Lower Peninsula of Michigan.

Six exclosures built in 1937 were all in overbrowsed deer-
yard swamps. Highly significant differences in amounts of avail-
able browse per stem were noted between the exclosures and their
controls for nearly all preferred and second choice deer food
species found there. American yew was absent from the control
areas. Highly Significantly less browse per stem was found on
white cedar, hemlock, red-osier dogwood, alternate-leaved dogwood,
mountain-ash, red maple, black ash, aSpen, silver maple, swamp
and American fly honeysuckles, white birch, basswood, and willow
in the control areas. Balsam fir was the only starvation food
Species with significantly less browse per stem in the control

areas.

Ten exclosures built in 1950 were scattered widely. In
some areas where deer were evidently not numerous, self-pruning
had significantly reduced the per cent of available white cedar
browse. Where deer were moderately abundant, differences be-
tween browse conditions in excluded and control areas generally
were not significant, but highly significant differences existed
for preferred deer food Species between these locations and un-
browsed areas. In heavily pOpulated areas, as indicated by a
definite browse line, all preferred, second choice, and even
balsam fir of the starvation diet species had been severely
browsed. Even during the six months Since the exclosures had
been built many significant differences were found in browse

availability within and without the exclosures.

REFERENCES CITED

. Bartlett, I. H. 1950. Michigan deer. Game Division, Michigan
Department of Conservation. 11,27.

Davenport, LaVerne A. 1939. Results of deer feeding experiments
at Cusino, Michigan. Transactions of the 4th North American
Wildlife Conference. American Wildlife Institute. Washing-
ton, De Ce 268-2740

Fernald, M. L. 1950. Grey's manual of botany, eighth edition.
American Book Company, New York.

Manville, R. H. 1947. The Huron Mountain deer herd. Journal of
Wildlife Management. 11: 263-266.

Maynard, L. A., Bump, Gardiner, Darrow, Robert, and Woodward, J. C.
1935. Food preferences and requirements of the white-
tailed deer in New York State. New York State Conservation
Department, and New York State College of Agriculture. 21.

Michigan Department of Conservation, Game Division. Unpublished.
Notes and letters in Game Division file on Luther Baldwin

Swamp release cuttings.

Petrides, George A. 1941. Observations on the relative impor-
tance of winter deer browse Species in central New York.
Journal of Wildlife Management.. 5: 416-422.

Swift, E. 1948. Wisconsin deer damage to forest reproduction
survey - final report. Wisconsin Conservation Department,

publication 347: 4-7.

1950. A history of Wisconsin deer. Wisconsin Con-
servation Department, publication 323: 40, 60.

 

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