What do deer eat? / by Stephen A. Liscinsky, Charles T. Cushwa, Michael J. Puglisi, and Michael A. Ondik

m&S'n.lkSlk STAINS LIBRARY

docu>-i:e'Tts section

What Do Deer Eat?

By Stephen A. Liscinsky,
Charles T. Cushwa
Michael J. Puglisi
and Michael A. Ondik

Reprinted from PENNSYLVANIA GAME NEWS
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What do deer eat?

FIG. 1 — REGIONS based on physiographic and vegetative criteria.

What Do Deer Eat?

By Stephen A. Liscinsky, Charles T. Cushwa,
Michael J. Puglisi, and Michael A. Ondik

A lmost everyone wants to

know what deer eat. Students,
teachers, farmers, hunters, nature
lovers, biologists, land managers and
planners— all are interested in the food
habits of Pennsylvania’s state animal,
the whitetailed deer.

A short simple answer might be
that deer are primarily vegetarians, al-
though they have been known to eat

Stephen A. Liscinsky is a uildlife
biologist with the Pennsylvania Game
Commission’s Division of Research;
Charles T. Cushwa is Program Leader,
Institute of Northern Forestry, U.S.
Forest Service, Fairbanks, Alaska, and
formerly assistant leader of the Penn-
sylvaia Cooperative Wildlife Research
Unit at Pennsylvania State University;
Michael }. Puglisi is a research as-
sistant in the Institute for Research on
Land and Water Resources at P.S.U.,
and Michael A. Ondik is a research
assistant in the Wildlife Research Unit
at the same university.

meat. But such a short answer seldom
satisfies those who inquire; they want
something more specific and those
who are responsible for deer habitat
improvement certainly need more de-
tailed information. In addition to
knowing exactly what deer eat, habitat
managers need to know how rhuch
they eat, and when and where they
eat it. These men also need to know
how important various foods are in
the diet of deer during all seasons of
the year.

This information can be, and has
been, acquired by a number of meth-
ods. Recently, the Pennsylvania Game
Commission, in cooperation with the
Pennsylvania State University Wildlife
Research Unit, used stomach content
analysis technique to determine the
seasonal and regional uses of food by
whitetailed deer.

The state was divided into seven
regions based on physiographic and
vegetative criteria (Fig 1). A few
game protectors in each region were

assigned the task of collecting a dozen
samples each season from road-killed
deer. The rumen content samples were
preserved in one-quart jars containing
two cups of 10 percent fonnalin, and
the date and location of each sample
was recorded. In all, 1028 samples
were collected and forwarded to the
Wildlife Research Unit laboratory
where they were analyzed by wildlife
biologists from the Game Commission
and the Research Unit.

The samples were washed through
a series of three sieves to separate the
fine from the coarse particles of food.
Only the coarse particles were re-
tained for examination as earlier stud-
ies had shown that the proportions of
various food items in the fine particles

FIG. 2 — Seasonal foods of deer, based on
importance values. Study the area taken
up by each category, not the height of the
line above bottom.

FIG. 3 — Seasonal use of leaves from
woody plants by deer, based on importance
value. Use is associated with seasonal
availability.

were about equal to those in the
larger pieces, and that it takes about
ten times as long to separate and iden-
tify the small particles as it does the
large ones.

Material that did not pass through
the sieves was emptied onto large
aluminum sheets and separated by
species, when recognized, according
to plant parts as fruit, green leaves,
dead leaves, succulent twigs, and
hardened twigs. Materials that could
not be identified by species were sep-
arated into grossly different categor-
ies. The volume of each item was
measured by water displacement.

Some foods showed up frequently
but in small volume, others were
found in large volume but low fre-
quency; and still others were found
in combinations of these two char-
acteristics.

OTHER

PEAR

BLACKBERRY

DEERBERRY

BLUEBERRY

ROSE

HAWTHORN

RAPE

SUMAC

ilarities in the use of the
various parts of woody
plants. When fruits are
readily available during the
fall and summer, for ex-
ample, they make up a larger portion
of the diet. On the other hand, leaves
are eaten uniformly throughout the
year and the use of evergreen leaves in
the winter compensates for the ab-
sence of leaves from deciduous plants.
The stems from woody plants make up
about 20 percent of the diet and this
remains rather constant throughout
the year. The importance of evergreen
stems and leaves is even more signifi-
cant, considering that only about 10
percent of our forests are evergreens.
The high and rather constant use of

FIG. 4 — Seasonal use of fruit from woody
plants by deer, based on importance value.

To better evaluate and illustrate the
frequency of occurrence and the vol-
ume, these two measured character-
istics were combined into one by
adding the percent of frequency to
the percent of volume and dividing
by two. This characteristic is called
the importance value. Using it, the
significance of both the volume and
presence of each item is maximized
and believed to be more realistic than
using volume or frequency above.

The findings of this study have been
summarized in the graphs that ac-
company this article. When examin-
ing Figs. 2 through 5, readers are
cautioned to study the area taken up
by each category, not the height of
any particular line above the bottom.

In Fig. 2, the seasonal foods of
deer based on importance value, note
the overall greater importance of
woody plants as compared to her-
baceous or non-woody material, and
also the seasonal differences or sim-

FIG. 5 — Seasonal use of broad-leaved her-
baceous plants, based on importance value.

REGIONS

FIG. 6 — Seasonal and re-
gional use of deciduous
stems by deer, based on
importance value. Use of
stems was quite similar
in all seasons and all
regions.

STATE

WIDE

IMPORTANCE VALUE

SPRING

□

SUMMER

□ =

FALL

= WINTER

herbaceous plants, an average of about
30 percent, shows the importance of
thisj:)lant group.

A closer look at the use of leaves
from woody plants (Fig. 3) reveals
red maple, cherry, blueberry, grape,
and oak were the most prevalent in
summer, while hemlock, laurel and
pine were more prevalent in the
winter. Note how closely use is as-
sociated with availablity.

Apples and acorns were important

as indicated in fruits. Fig. 4. It
should be mentioned that there was
an exceptionally large crop of apples
produced during the time of the sur-
vey. Nevertheless, even during normal
or average years, the use of apples
by deer is rather high. Acorns too
play a very important role in the diet
of deer even though, like apples, their
production is erratic and variable from
place to place. It may surprise you
to note the presence of fruits of cherry,

FIG. 7 — Seasonal and
regional use of leaves by
deer, based on impor-
tance value. Importance
of leaves was quite dif-
ferent in different re-
gions and seasons. Note
importance of ever-
greens during the winter.

LWWil 0

r E

7

I "To

STATE

WIDE

;i I -'-f D

IMPORTANCE VALUE

S = SPRING □ = SUMMER EH = FALL ^ = WINTER
E -EVERGREEN D DECIDUOUS

blueberry, grape, blackberry and other
plants present in the stomach of deer.

Illustrated in Fig. 5 are the most
commonly occurring broad - leaved
herbaceous plants in order of relative
importance. Clover was apparently
a highly sought after food in spring
and summer. Other species such as
plantain, speedwell, trefoil, straw-
berry and cinquefoil were commonly
utilized to various degrees during the
four seasons. Many other herbaceous
plants were also used. Table I gives
the eomplete listing of all plants posi-
tively identified in the samples.

To show some regional differences
and or similarities of foods used by
deer it was necessary to single out
distinct species or groups of plants.
Fig. 6 shows that the use of stems from
woody plants was quite similar in
all regions and in all seasons. On the
other hand, the importance of leaves,
both evergreen and deciduous, was
quite different between regions and
seasons (Fig. 7). Note again the im-
portanee of evergreens during the
winter.

Acorns were more important in
some regions than in others, as indi-
cated in Fig. 8. These differences are
obviously caused by the presence or
absence of oak trees and/or acorn
mast. Acorn production varies from
year to year, and place to place with-
in and between species.

As w’Ould be e.xpected, large dif-
ferences also e.xisted between the
seven regions in the oecurrence of
corn in the rumens sampled. Fig. 9
shows corn occurred more frequently
in rumens from the farming regions
than in the forested regions. Even at
that, the winter use of corn, especially
in the low corn producing areas, is
surprising. Perhaps these values were
exaggerated by proximity of waste
corn in fields near woodlands and the
use of corn in “winter feeding pro-
grams.”

In general terms, seasonal dif-
ferences in foods were found to be
greater than regional differences.
About 60 percent of the diet year-

SPRING

SUMMER

FALL

WINTER

IMPORTANCE VALUE

FIG. 8 — Seasonal and regional use of
acorns by deer. Regional differences are
caused by the presence or absence of oaks.

round consisted of woody plants. The
importance of woody stems, leaves
and fruit changed with the seasons in
all regions. Fruit utilization was the
most variable, because of seasonal
availability. Leaves were an im-
portant year-round food, with ever-
green utilization inereasing when
deciduous leaves were less available.
Woody stems also were an important
year-round food, with hardened stem
utilization increasing when succulent
stems were less available.

It is obvious, however, that deer
make choices from what is available.
Succulent plants or parts of plants
were chosen over hardened vegetation.
Hardened twigs and evergreens were
used more when other sourees of food
were less available, and individual
species of plants or parts of plants
were utilized to various degrees and at

various times throughout the year.

In summary, it can be said that
deer utilize many kinds of food, their
choices being strongly governed by
the succulence and palatability of
whatever is available at a given time.
It follows that habitat management
for deer should be geared to making
food available when and where deer
need it most, in the most economical
fashion.

Table I

Plants, or Parts Thereof, Identified
in the Stomach Content Samples.

Woody Plants

Apple

Jack Pine

Arbor Vitae

Juneberry

Ash

Larch

Aspen

Mountain Laurel

Beech

Mulberry

Birch

Oak-

Blackberry

Orange

Black Cherry

Partridge-Berry

Black Locust

Pear

Blue Beech

Persimmon

Blueberry

Pine

Cherry

Pitch Pine

Chestnut Oak

Privet

Coralberry

Red Oak

Crab Apple

Red Cedar

Decrberry

Red Maple

Dewberry

Rhododendron

Dogwood

Rose

Elderberry

Sassafras

Elm

Spruce

Grape

Sugar Maple

Gray Dogwood

Sumac

Greenbriar

Sweet Fern

Hawthorn

Teaberry

Hazelnut

Tulip Poplar

Hemlock

Virginia Creeper

Hickory

White Pine

Honeysuckle

W'illow

Witch Ha'zel

Non-Woody Plants

Alfalfa

Bellwort

Aster

Cabbage

Bean

Canada Mayflower

FIG. 9 — Seasonal and regional use of corn
by deer. This food’s importance in low
corn producing areas might have been
exaggerated by winter feeding programs.

Plantain
Pokeweed
Potato
Ragwort
Rye

Slijeep Sorrel
Soybean
Speedwell
Spikenard
Spring-Beauty
Strawberry
Tomato
Trefoil
Violet
Wheat

Wild Geranium
Wild Mustard

Cantaloupe

Carrot

Cinquefoil

Clover

Club Moss

Cohash

Corn

Crown Vetch

Dandelion

Domestic Lettuce

Goldenrod

Ground Cherry

Indian Pipe

Liverwort

Mayapple

Milkweed

Oats

Panic Grass