LIBRARY.
A 8c M COLLEGE»

clggzgus .

BULLETIN NO. 591

i‘

TEXAS AGRICULTURAL EXPERIMENT STATION

A. B. CONNER, DIRECTOR,
College Station, Texas

f”.

A POPULATION STUDY OF THE GRAY

SQUIRREL IN EASTERN TEXAS

PHIL l). GOUDRUM

Division of Wildlife Research and Texas Cooperative Wildlife

Research Unit

 

AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS

T. 0. WALTON, President

AUGUST 1940

—T

A71-840-7M-L1 80

[Blank Page in Original Bulletin]

TAES

 

The gray squirrel is one of the most important game animals in
Texas, particularly in the eastern part of the State. Because of
its steady decrease in numbers the future game status of the
animal is threatened. The factors causing the decline 0f the
squirrel and some suggested practices that will help to conserve
it as a game resource were studied and this bulletin contains
reports of this study.

Destruction of favorable habitat and improper and inadequate
laws governing the shooting seasons have been the primary factors
in gray squirrel decrease. Lack of proper regard for biological
principles in harvesting forest trees and grazing the bottomlands
either has reduced the quantity of squirrel habitat or in some
instances completely destroyed it. A reversal of these practices,
even in part, will help to restore these fine game animals in many
sections.

Instead of a large number of county laws, the regulations should
be regional in application; and instead of seeking the supposed
convenience of the hunters, the statutes should be based on the
life history of the squirrels. At present many of the permitted
open seasons conflict with the breeding periods of the squirrels
and so result in losses out of all proportion to the hunting done.
These studies show that the principal crop of young squirrels
occurs in the early spring although there is a second breeding
season in the late summer, and in some cases breeding occurs
throughout the year. For practical purposes therefore two closed
seasons are indicated for the period December 15 to May 1 and
other from May 15 to October 15 in order to permit reproduction
with the least interference from hunters.

10'?%923

CONTENTS

Page
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5

Methods and Materials Studied . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6

Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6

Location of Study Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6

Census Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7

Time-Area Counts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8

Leaf and Twig Nest Counts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8

Hunting with Dog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8

Habitat Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9

General Nature of Gray Squirrel Range . . . . . . . . . . . . . . . . . . . . . . . . 9

Classification of Habitat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9

Squirrel Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10

Eflect of Habitat Type on Population . . . . . . . . . . . . . . . . . . . . . . . . .. 10

Migration Fluctuation and Densities . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13

Ecological Factors Affecting the Population . . . . . . . . . . . . . . . . . . . . . . .. 14

Notes on Life History as related to Squirrel Numbers . . . . . . . . . . .. 14

Cruising Radius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14

Breeding Habits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 15

Size Brood Relati ns and Gregariousness . . . . . . . . . . . . . . . . . . . . . . .. 17

Temperament . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Voice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Nests . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Emasculation of Young . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 18

Local Movements and Causes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19

Effects of Lakes and Ponds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Leafing and‘ Flowering of Vegetation . . . . . . . . . . . . . . . . . . . . . . . . .. 20

Climate as ‘Affecting Squirrel Populations . . . . . . . . . . . . . . . . . . . . .. 2

Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 21

Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Food Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 21
Food Habits as Shown by Stomach Analyses and Field Observations 22
Squirrel Mortality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 23

Parasites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 24

Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 24

Modification of Habitat by Man . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 25

Timber Cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 25

Grazing by Livestock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26

Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26

Economic Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27

Damage to Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27

Control of Insects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27

Sources of Fur and Food . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27

Objects of Sport and Monetary Returns . . . . . . . . . . . . . . . . . . . .  .. 27

Relation to Domestic Animals and Other Wildlife . . . . . . . . . . . . . . .. 28

Habitat Improvement and Management Practices . . . . . . . . . . . . . . . . . . .. 28

Environmental Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 28

Creation of Ponds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 29

Effect of Hunting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 29

Squirrels and The Texas Game Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 30

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 32

Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 32

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . .  . . . . . . . . . . . . . . . . . . . . . .. 34

A POPULATION STUDY OF THE GRAY SQUIRREL,
S-CIURUS CAROLINENSIS CAROLINEN-
SIS, IN EASTERN TEXAS

PHIL D. GOODRUM*

Division of Wildlife Research and the Texas Cooperative Wildlife
Research Uniti"

The gray squirrel, Sciurzzs carolinensis carolinenses, is one of the most
important game mammals in eastern Texas. With the exception of its
relative the fox squirrel, Sciurus niger rufiventer, the gray squirrel is
hunted by more people of the region than any other game animal or bird.
As food, the species is preferred to other small mammals, and it is more
easily obtained than any of the larger native animals. Indeed, in many
localities the gray squirrel is sought mainly for food. It is superior to
the fox squirrel both as a table delicacy and in sporfling qualities. It makes
an appeal to all classes of hunters, from the small boy with his rifle or
slingshot to the experienced hunter with a repeating shotgun.

The fact that a great many persons keep squirrels in _cages attest the
value of these animals as objects of esthetic interest. Squirrels are not
difficult to see in the wild and many persons go into the woods just for this
purpose. Seton (1928) summed up the esthetic value of the gray squirrel
when he said that “it supplies to the city man, the farm boy, and the
sportsman, the most alluring motive for a glorious tramp in the ever-
inspiring woods, with a sufficiency of material reward, an amplitude of
present joy, and a heritage of delightful memories.”

Seton (1928) in the United States, Middleton (1930) in the British Isles,
and other Workers have published data on population of the gray squirrel,
but none has dealt with this species in the southern states.

Previous to 1910 the gray squirrel was abundant over the entire eastern
Texas region Wherever suitable habitat was found. Deer and turkey were
common, and the people seldom killed squirrels except as a protection
against depredations on corn crops. As the country became settled and
larger species of game dwindled in numbers, the people began to hunt
squirrels, utilizing most of them for food. Experiences of old-timers and
sportsmen indicate that in Texas the gray squirrel began to decrease about
1910. Between 1915 and 1920, through the general use of the repeating
shotgun, large numbers of the animals were killed for the sheer fun of it.
Furthermore, beginning about 1915 and continuing unabated up to the

*Director, Division of Wildlife Restoration, Texas Game, Fish and Oyster Commission.

iThe Texas Cooperative Wildlife Research Unit is supported by the Agricultural and
Mechanical College of Texas, The Texas Game, Fish and Oyster Commission, The Ameri-
can Wildlife Institute and The Fish and Wildlife Service, U. S. Dept. of the Interior,
cooperating.

6 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

present, the logging of hardwoods has brought about a drastic reduction
of suitable gray squirrel environment. The last 12 years have witnessed
a gradual increase in livestock production, resulting in overgrazing in

some sections. This has further reduced and injured the habitat of the.

gray squirrel through the removal of food producing seedlings and the
general thinning of vines and other shelter plants. Many areas formerly
occupied by squirrels now have none.

Apparently little attention has been given to conditions affecting squirrel
occurrence and numbers. For this reason studies of population were begun
in May, 1936. It appears that if measures are not taken to protect and
encourage the species it will ultimately be eliminated as a game animal.
A complete revision of the squirrel laws is urgently needed. To obtain
optimum conditions, however, management practices also must be insti-
tuted along sound biological lines.

METHODS AND MATERIALS STUDIED

Sources of Information

Most of the data for this paper were collected during the years 1936 and
1937 as part of a life history study of the gray and fox squirrels of
eastern Texas.

Examination of 541 specimens, censusing, analysis of stomach contents
of 87 squirrels, field observations and notes, interviews with sportsmen,
woodsmen, and landowners over a 2-year period constitute sources for
the information here presented. Robert McClanahan and Leon Kelso of
the section of food habits, division of wildlife research, United States
Fish and Wildlife Service, analyzed 87 of the 300 or more gray squirrel
stomachs collected.

Location of Study Areas

The region covered in this study includes all of the pine-oak-hickory
lands of eastern Texas (Figure 1). The area selected for intensive study was
the Weiser Bottom Game Preserve and the adjoining Texas Prison System
pasture located in the bottomlands of the Trinity River 16 miles southwest
of Trinity, Texas, in Walker and Trinity counties. The soils of the area
are mostly of alluvial Trinity clay, interspersed with dark sandy loam
along the hammocks (low sandy ridges) and subject to overflow. The
entire area is heavily forested with hardwoods. An occasional loblolly
pine (Pinus taeda) may be seen, however, on the hammocks. Grazed and
ungrazed plots were present in the area. The Texas Prison System
pasture was open to hunting whereas the Weiser Bottom Game Preserve
W35 ClUSHl. Several fiXllfilldfid VlSltS were made to other portions of eastern
Texas for the purpose of making additional field studies. These included
areas in Angelina County and in the Texas Big Thicket region, 20 miles
southeast of Livingston, Polk County.

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS 7

_ ._._—-..—»-~
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nu“; page; nut-awn] nous-vs 001w I

Fig. 1. The black square shows the area of intensive work, which lay principally in
the bottomlands of the Trinity River in Trinity and Walker counties. Con-
clusions should be of significance in all counties east of the black line and
perhaps also in the counties of Leon, Madison, Grimes, Brazos, Washington,
Austin, Colorado, Lavaca, Jackson, Wharton, Fort Bend, Brazoria, Matagorda,
and Calhoun, although no investigation was made in any of them.

Census Metho-ds

Although considerable literature is to be found on counting and estimating
wild populations of various species of birds and mammals there is little, if
any, on the gray squirrel.

Leopold (1933) has discussed techniques of measuring wildlife popula-
tion. Dice (1931) suggested that the best method of determining abundance
of mammals was to list the number of individuals observed in each
ecological type of habitat. Chapman (1937) working in Ohio on con-
trolled squirrel hunting, discussed the value of taking a census but did
not describe the methods used except to give kill records. None of these
methods has been found strictly applicable to the problem of estimating
squirrel populations under eastern Texas conditions, although all have been
helpful, especially an adaptation of the methods proposed by Dice.

8 BULLETIN NO. 591. TEXAS AGRICULTURAL EXPERIMENT STATION

The methods found most effective in estimating gray squirrel populations
in eastern Texas are: ,
1. Time-area counts of the number of squirrels on sample plots selected
at random over the tract to be censused. I
2. Counting leaf and twig nests on a given strip of forest cover of different
types, preferably in late fall and early Winter.
3. Hunting with dog.

Time-Area Counts

In making time-area counts, plots were chosen at random in representa-
tive cover at a time when the quirrels were most active, usually before
sun-up in the morning. For 20 or 30 minutes the observer remained quiet
and counted all squirrels that showed themselves. Then by pacing, ‘with
the aid of a tally register, the average distance that a squirrel could be
seen was determined. This distance was taken as the radius of the circular
area that could be watched from the observation point and from this the
area was computed. Since not more than three-fourths of the circular area
could be observed Without moving, only three-fourths of the area was con-
sidered and the number of squirrels seen therein was recorded. Enough
counts were made in each representative type of cover to insure significance
of figures derived. From these data the number of squirrels per acre was
computed. To facilitate calculations a table was constructed giving in
square feet the number of acres for a number of different radii. The total
population of an acreage was determined by multiplying the average
number of squirrels per acre by the number of acres in the tract of similar
type. The greater the number of counts and the more uniform the ‘vege-
tational type, the more accurate was the census. For each count a careful
record was kept of the number of squirrels observed, exact location, time
of day, date, size of area, and type of vegetation.

Leaf and Twig Nest Counts

Leaf and twig nests were counted in strips of woodland, preferably in
late fall or early winter. The number of acres in strips on which the
counts were made was carefully estimated by pacing with a tally register.
For this purpose a table of calculations was employed. As in time-area
counts, all pertinent data were recorded. Several counts were made over
each tract censused. In late fall and early winter one can rely on seeing
about one nest to each two squirrels present. '

Hunting with Dog

Squirrel hunting with a dog was done at a time When the squirrels
were active on the ground. The number of squirrels treed each hour in
each ecological type was recorded. The same dog was used throughout
the study. A detailed record was kept of the hour that each squirrel was
treed, kind of tree, species of squirrel, and other information of a general
ecological nature.

13am“. u

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS 9

HABITAT TYPES
General Nature 0f Gray Squirrel Range

The gray squirrel inhabits the heavily forested areas along the rivers
and larger creeks of eastern Texas but occasionally one will be found on
the borders of smaller creeks and ravines and in adjacent pine Woodland.
In all probability squirrels were present during the pioneer days in con-
siderable numbers along all creeks large enough to supply water throughout
the year. Of late, however, many of the creeks have become intermittent,
forcing the animals to occupy more favorable areas. In England (Mid-
dleton, 1930) the introduced American gray squirrel is confined to the
valleys and never found in dense stands of conifers, a condition much
like that in this country. Since practically all of the gray squirrels now
are confined to the larger flood plains or other well-watered and forested
areas in eastern Texas, field work was carried on in those areas with a
view to determining the relative value of the different types of habitat.
Wight (1931) and Leopold (1933) have described various methods of evalu-
ating game range, pointing to the value of considering types of habitat
and interacting factors. Their ideas have been kept in mind in Working
out habitat types for squirrels. Previous work of the present writer
(1937b), with additions, has been incorporated here.

Classification of Habitat

Three types of squirrel habitat now are recognized along the flood
plains of eastern Texas. In descending order of their carrying capacity,
these are as follows:

Hammock Type. Low, sandy loam ridges scattered along the flood plains
of the larger streams of the region. The vegetation is mixed and varied,
consisting chiefly of white oak (Querczzs alba), water oak or pin oak
(Q. nigra), magnolia (Magnolia grandiflora), linden (Tilia sp.), sweetgtim
(Liquidambar styraci_fiua), holly (Ilex opaca), yaupon (I. vowtitoria), sum-
mer huckleberry (Vaccinium virgatum), grapes (Vitis sp.), and mulberry
(Morus rubra). The understory is rather dense and the crowns of larger
trees are not crowded. A large percentage of hammock occurs in eastern
Texas along all streams except the Trinity River. In some places loblolly
pine (Pinus taeda) is present in considerable numbers.

Poorly Drained Bottomland. Lower, fiat, or depressed areas of the flood
plains. The willow oak or pin oak (Querczts phellos), evergreen oak
(Q. rhombica), elm (Ulmus fulva), overcup oak (Q. lyrata), bitter pecan
(Hiicoria aquatica), black gum (Nyssa sylvaticct), cypress (Taxod/imn
distipcltzlwz), ash (Fraaoinus sp.), ironwood (Carpinus carolivizicnza), and
palmetto (Sabal sp.) are characteristic of the plant cover. Shrubs are
largely absent and several species of sedges constitute the herbaceous
cover. Ponds occur over areas of this kind and are usually contiguous
to hammocks.

10 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

Well Drained Bottomland. Higher and better drained sections of the
bottomlands. The most common plants are postoak (Quercus stellata),
haws (Crataegus sp.), hackberries (Celtis sp.), Texas red oak (Q. shu-
mwrdii and schneckii), gum elastic (Bumelia lanuginosa), basket oak (Q.
macrocarpa), elm (Ulmus crassifolia), and pecan (Hicoria pecan). Ponds
and lakes are few in the well drained type; however, water is available
along the streams.

A cover type map of 7,565 acres of the bottomland 16 miles southwest
of Trinity along the Trinity River where most field work was done (see
page 7) showed that 56 per cent of the area consists of the well drained
type, 27 per cent poorly drained type, and 17 per cent hammock. This
proportion of vegetational types does not hold true for squirrel habitat
in Angelina County nor the Texas Big Thicket, in which sections the
hammock type predominates. The principal cause of this variation may
be found in the soil. The soils along the Trinity River are mixtures of
silt, clay, and sand, while those along other streams are of light silt-
sand combinations.

SQUIRREL NUMBERS
Effect of Habitat Type on Population

After classifying the gray squirrel range into three types of habitat as
discussed in the foregoing pages, an effort was made to determine which
of these types was used most by the animals. It was found, as any good
squirrel hunter knows, that gray squirrels prefer the hammock type above
all others. A census of the three types by the time-area count method
showed a population density of 1.42 squirrels per acre for the hammock
type, .87 for the poorly drained type, and .67 for the well drained type.
(See Table 1.) In order to check these figures other methods of esti-
mating the squirrel population were employed; i. e., counting nests on
sample plots and counting the number of squirrels treed per hour by a dog.
The results obtained substantiated the time-area counts. (See Tables 2
and 3.) It may be pointed out, however, that the dog treed a greater

Table 1. Abundance of squirrels by type as indicated by time-area counts on sample plots

Counts made on Weiser Bottom Game Preserve (7.000 acres), Trinity River. Trinity
and Walker counties, Texas, between August, 1936, and September, 1937.

Number

Type of Habitat Number Number of Gray Squirrels

of Counts of Acres Squirre s Per Acre
Ilammock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 22.5 32 1.42
Poorly drained bottom . . . . . . . . . . . . . . . . . . . .. 23 18.25 16 .87
\Vcll drained bottom . . . . . . . . . . . . . . . . . . . . . . . 24 17.85 12 .67
Totals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 58. 60 6O 1.02

 

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A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS 11

Table 2. Abundance of squirrels by type as indicated by counting leaf nests
Counts made 0n Weiser Bottom Game Preserve (7,000 acres), Trinity River. Trinity

and \Valker counties, Texas, between July, 1936, and November, 1937. '

Type of Habitat 01;Il(l:IO1ll)Ii{S (liflullglldsils (liiuilctiig Pgejrtcsre
Hammock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 227 360.9 .62
Poorly drained bottom . . . . . . . . . . . . . . . . . . . .. 11 101 177.9 .51
Well drained bottom . . . . . . . . . . . . . . . . . . . . . . 10 112 294.4 .37
Totals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 440 833.2 .50

Table 3. Abundance of squirrels by type as indicated by number treed by dog in 141 hours
of hunting

(About equal number of hours hunting each type.)

Counts made on Weiser Bottom Game Preserve (7,000 acres), Trinity Biver, Trinity
and Walker counties, Texas.

Squirrels Per Hour
Period Poorly Well
Hammock Drained Drained
Bottom Bottom
June to October, 1936 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.7 6.5 3.1
November, 1936, to l\/Iay, 1937 . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 2.5 .8
Average for year . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.9 4.4 1.9

number of squirrels in the poorly drained habitat than in the hammock
type, but this is regarded as not depicting the true population density
for it is much easier for the dog to see squirrels in this type because
the understory is much less dense than in the other two types. Although
dogs find some squirrels by trailing, a far greater number are found
by sight.

Estimating a squirrel population by counting the number of squirrels
seen on sample plots during a given interval is the most accurate method
yet devised but is time-consuming. In most practical game management
programs relatively little time is available for making accurate censuses
of game. In view of this fact, counting of squirrel nests on estimated
plot sizes is recommended as a quick way to estimate the squirrel popula-
tion of an area. The best time to make a census of this kind is in the
fall just prior to opening of the hunting season in October because the
dried brown leaves of the nests stand out in bold relief against the
background of green foliage.

a Gray squirrels prefer the hammock type of habitat because it affords

 a greater diversity of food and cover at all seasons of the year than
 either the poorly or Well drained areas. As pointed out earlier, hammocks

12 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

Fig. 2. Eastern Texas Big Thicket Type of Hammock Showing Water Oak, Beech,
Magnolia, Loblolly Pine, Blackgum, and Understory of Shrubs, Making Ex-
cellent Habitat for Gray Squirrels.

Photographed March 21, 1937 by D. W. Lay. Texas Cooperative Wildlife Research
Unit No. A879.

have well developed understories of shrubs and vines of many species
whereas the other types are often composed of pure stands of trees and
shrubs of few species and oftentimes only one species such as elms. Vines in-
termingled with Spanish moss constitute excellent refuge cover for squirrels.
On the hammocks, trees such as sweetgum, water oak, white oak, and
magnolia usually do not grow in dense stands, which permits them to
develop large crowns above the understory, thus making it possible to
produce a larger and more consistent crop of mast. In addition to this,
these trees are invariably selected as breeding and brood rearing sites.
Although pure stands of Willow oak do yield bumper crops of acorns, these
crops occur only once every 3 to 5 years. In winter, after the leaves
have fallen, few squirrels are found in these areas because there is little
cover for them; then, too, suitable hollow trees are scarce. Elms, however,
constitute an important source of winter food in the form of buds, but
only those trees near good cover, as is found on hammocks, are exten-
sively utilized.

wnwwwflfjw. wma.;,, . . . L, ., . _. , ..

 

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS, 13

Migration, Fluctuation, and Densities

Fluctuations in gray squirrel numbers have been noted since 1740.
Seton (1928) and Edminster (1937) assert that the gray squirrel is cyclic
in the northeastern portion of the United States. Others have recorded
sudden decreases of squirrels and have attributed them to a number of
causes, foremost being migration. Seton (1928) lays the northern migra-
tions to overpopulation even when food is plentiful. Chapman (1936) says.
that overpopulation and food shortage were the causes of migrations in
Ohio. Goodwin (1934) describes a gray squirrel migration of wholesale.
proportions in the New England states in 1931 and 1933, referring to]
many drowned in crossing streams and to numbers killed on the highway..
Jackson (1921) cites an occasion in 1914 when considerable numbers of
the northern gray squirrel swam the Mississippi River in Wisconsin.

Middleton (1930) and Parsons and Middleton (1937) say that the intro-
duced American gray squirrel has steadily extended its range since 1890
in the British Isles. Middleton is quite certain that extension is not due
to movement of wholesale numbers or overpopulation but rather to indi-
viduals possessing the migratory instinct. He gives proof where an exten-
sion of 35 miles was made in 5 years from an area where the squirrels
were remarkably scarce. A

The writer has never witnessed squirrel migrations of the character
reported in the north. An observer, W. J. Cox, near Corrigan, Polk County,
Texas, however, related that in the fall of 1928 he saw a number of gray
squirrels in a group going south through the woods. John Knight, Segno,
Polk County, told of seeing several gray squirrels swimming the Trinity
River" in the fall of 1929. It is likely that these movements were only
local and, therefore, cannot be considered as a migration. It is believed
by many persons in eastern Texas that gray squirrels move in and out
of given areas at frequent intervals. In general, this is true, but since
most movements are usually confined to one body of unbroken woodland,
seldom over 5 miles in extent, such movements cannot strictly be called
migrations.

Several observers reported an abundant squirrel crop for the year 1929
in the entire eastern Texas region and a small crop for 1936 and 1937.
Data on the Weiser Bottom Game Preserve, protected since 1926, show
that squirrels decreased in number between 1929 and 1931. From 1931
to 1936 no change was noted in the number of squirrels. A census of the
7,000 acres in 1936 and 1937 showed a drop from 9,380 in 1936 to 7,980
in 1937, a decrease of 13.8 per cent (Table 4). The exact cause of‘
this is not known. Examination of 8 pregnant females in 1936 revealed
an unborn litter size of 3, whereas in 8 specimens examined in 1937 the-
average was 2.5, a 16 per cent decrease in size of litter. It is possible-
that the number of young born was not sufficient to ofiset the loss by
natural causes, thus causing a decrease in the population. Theodore Turney
of Weldon found 3 dead squirrels in the area in 1931 and 2 early in 1938.
The latter were taken by the writer to the Texas Agricultural and Mechan-

14 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

Table 4. Calculated abundance of squirrels in 1936 and 1937 as indicated by time-area counts
in August and September in all types of habitat in an area protected
from shooting for 10 years

Counts made on Weiser Bottom Game Preserve, Trinity River, Trinity and Walker
_ counties, Texas.

Number Number Number
Year of of Acres of Squirrels
Counts Censused Squirrels Per Acre

1936 . . . . . . . . . . . . ._ . . . . . . . . . . . . . . . . . . . . . . .. 26 7,000 9,380 1.34
1937 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9 7,000 7,980 1 .14

ical College for examination. Putrefaction had progressed too far for an
accurate diagnosis but there was sign of internal injury, indicating they
had been shot. There is as yet no available evidence pointing to disease
as a probable cause of the decrease in squirrel numbers in eastern Texas,
and the causes of gray squirrel fluctuations in the regions remain to be
definitely determined. It may be inferred, however, that the decrease in
acorns in 1936 and 1937 over the entire eastern Texas region (except in
localized areas) may be, in part, the cause of reduction.

The time-area census showed that ideal habitat under protection in
eastern Texas carried 1.02 squirrels per acre. Middleton (1930) working
in the British Isles, counted a kill of 1,000 squirrels on 500 acres, a density
of two per acre. He estimated that this number was about three-quarters
of the total population. There is a possibility that, under proper manage-
ment, the squirrel population in eastern Texas could be approximately
doubled. '

ECOLOGICAL FACTORS AFFECTING THE POPULATION
Notes on Life History as Related to Squirrel Numbers

In common with a great many diurnal species of wildlife, gray squirrels
begin the daily routine at break of day or even earlier, depending upon
weather conditions. Unlike fox squirrels which may be abroad at any
hour of the day, gray squirrels almost cease activity after about 9 a. m.
In late afternoon they again become active. They spend a great deal of
time on the ground digging in the soil for food. Sherman Hubbard, for
45 years an experienced Woodsman and squirrel hunter, says that squirrels
will come out and feed on bright moonlight nights, especially during sum-
mer and fall. Other persons, including the writer, have also seen gray
squirrels out at night. They are easier to find on days following dark
nights than on days following moonlight nights.

Cruising Radius

Although gray squirrels are rather mobile during spring and fall, par-
ticularly in the fall, they do not roam far from their headquarters in

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS 15

summer or winter. Certain individuals have been seen repeatedly in the
same locality over a period of 3 months. During hunts with dogs, several
instances have been recorded where individual squirrels have been chased
200 yards through the woods to the home tree, passing up many ideal
places for refuge. This indicates a home range of 200 yards or less. Mid-
dleton (1930) observed that gray squirrels in Great Britain seldom trav-
eled more than 100 yards from headquarters. Seton (1928) says that a
gray squirrel may live its entire life in a 100-acre plot. It appears then,
from this meager evidence, that the cruising radius is less than 200 yards.
No reliable information is available on the yearly range, but it is sus-
pected that in eastern Texas it may be as great as 5 miles, depending
upon food and climatic conditions and continuity of forest cover. It is
surprising how reluctant the gray squirrel is to take to a tree when
surprised on the ground a distance from its home tree. Dogs have cap-
tured squirrels under such circumstances. The obvious attachment of the
gray squirrel to a home tree suggests the importance of protecting such
trees Where squirrels are desired. ‘

Breeding Habits

Information on breeding habits of the gray squirrel has been secured
by observations in the field and by examination of freshly killed speci-
mens. Squirrels have been collected in all months of the year which were
either rutting, pregnant, or suckling young. In an early account (1938)
the writer has shown that gray squirrels have two principal breeding sea-
sons each year, one in the winter and the other in the summer. The larger
percentage of young are born in late winter. Data collected by Hibbard
(1935) in Kentucky also show two breeding seasons with larger litters in
winter. The rut begins about December and the peak of winter pregnancy
is reached sometime in January (Figure 3) or early February. The
summer breeding season begins late in May or early in June and
reaches the peak of pregnancy in August with 47.3 per cent of adult
females collected that month being pregnant, although Figure 3, because of
late lactating females, shows September as the height of the summer
breeding period. Deanesly and Parkes (1932), working in England, have
submitted partial evidence that the oestrus period in gray squirrels lasts
about 2 weeks. According to Seton (1928), quoting Bailey, the gestation
period is 44 days and the suckling period of the young about 6 weeks. In
the light of this information, the length of each breeding season is about
3% months. Deanesly and Parkes (1932) have shown that an individual
squirrel may have two litters of young each year. Examination by the
writer of 16 pregnant females in 193-6 and 1937 has shown an average
litter size of 2.7 unborn young. Deanesly and Parkes found the average
litter size in England to be 3.5, while Hibbard (1935) places the average for
Kentucky at 2.6. I

It has been difficult to determine accurately the breeding season of the
gray squirrel because of the occurrences of early and late breeders and

Y

16 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

Fig. 3. Breeding Peaks as Determined by Examination of 135 Female Gray Squirrels.

the retiring habit of pregnant females. This seclusive habit must be an
important factor in the perpetuation of the species. Of 244 females of
all ages collected, 135 were of breeding age. Of the 135, 24' were pregnant,
7 were in heat, and 17 were lactating, making a total of but 48 or 35.5
per cent in breeding condition. Compared with the total number of females
examined the number of breeding squirrels is surprisingly small.

Since the gray squirrel is polygamous, it may congregate in great num-
bers. Brady Thompson, an experienced Woodsman and hunter, counted 34
individuals in two trees in December 1929; other observers have estimated
as many as 100 in a few trees and on the ground nearby. Obviously, under
such conditions it is often easy to slaughter the animals in considerable
numbers.

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS 17

Size, Brood Relations, and Gregariousness

There is no way of telling the exact age of squirrels, but something can
be learned by comparing Weights of individuals and by examining the sex
organs. By examining the uteri, Deanesly and Parkes (1932) obtained
conclusive proof whether or not females had bred. The uteri of breeding
females are discolored and longer than those that have never bred. Chap-
man (1988a) estimated the ages of gray squirrels in Ohio by weighing.
At the time young squirrels emerge from the nest they Weigh approxi-
mately 200 grams. Adults weigh about 500 grams. Generally, if an indi-
vidual weighs under 400 grams it is less than 6 months of age.

After birth young gray squirrels remain in family groups for about 41/;
months. Young squirrels do not venture far from the home tree and when
one member of a group is found it is almost certain that others can be
located nearby. Hunters know this and take advantage of it; predators
probably do likewise. Kill records show that more squirrels are taken in
the months of May and October than in any other months; this doubtlessly
results from the delayed dispersal of the family.

Unlike the fox squirrel, the gray squirrel is notably gregarious and, as
already pointed out, often it is found in considerable numbers in favored
localities. Perhaps this habit is helpful or even essential in defending its
range against the larger and more pugnacious fox squirrel. On one occa-
sion, William Davis witnessed a fight between one fox squirrel and three
gray squirrels. By mass attack the gray squirrels were able to put the
fox squirrel to flight but against an individual gray the fox squirrel prob-
ably would have won the battle.

Temperament

The gray squirrel is nervous and easily frightened and when disturbed
it will move readily from its hiding place. This habit makes it superior
to the fox squirrel as a game animal. Once routed from hiding, it will
run with great speed through the tree branches or jump directly to the
ground in an effort to escape. All tree squirrels are more easily located
when they move. Fox squirrels depend upon the habit of moving and
turning slightly upon the branches to evade their enemies. A gray squirrel,
upon first notice of a suspected enemy, will remain perfectly quiet for a
few minutes, but upon disturbance will take to flight. The hair on the
tail stands on end giving it a bushy appearance which makes the animal
still easier to see. Even when a gray squirrel remains perfectly still upon
a limb, its tail may be blown by the wind thereby betraying it to the
observer. The tail also acts as a rudder as the squirrel races up and
down branches; without it the animal never seems to be sure, of itself.

Voice

The gray squirrel is normally one of the noisiest of tree squirrels, indeed
its frequent barking often reveals its presence to the hunter. A great
many sportsmen pursue the animals by creeping slowly through the forest

18 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

or by remaining perfectly quiet until the squirrels begin to chatter; then
they stalk them. Although no definite proof can be offered that barking
attracts the attention of natural enemies it is likely that an occasional
individual is captured as a result of its calls. Seldom, however, does the
squirrel bark while it is on the ground. As a rule, its vociferant cries are
emitted from a position in the lower branches of trees, where, obviously,
it has a better opportunity than on the ground for defending itself against
attack.

Field observations indicate that the voice during the mating season or
prior thereto is unlike that at other periods. At this time it has more of a
musical sound. Seton (1928) describes it as a sort of song, a “loud quack-
quack-quack quaaaaaaaaa, quack-quack-quack-quack-quack-quaaaaaaaaaa.”
The latter part of the series is a high pitched whine. The most common
and characteristic sound is a loud but emphatic mufiied “cherk, cherk,
cherk,” repeated rapidly and followed by heavy buzzing, often interpolated
with a grunt. The squirrels seem to use the voice to keep in touch with
each other. They also seem to congregate so that they may be in hearing
distance of each other. '

Nests

One important indication of the presence and abundance of squirrels is
the occurrence of summer leaf and twig nests. In the spring, beginning
in May, squirrels construct nests of twigs and leaves as resting and refuge
places. As the green leaves begin to dry, nests may be spotted easily.
Occasionally, the young, usually born in hollows of trees, will be transferred
to these nests by the mother. When the young become of age, they con-
struct nests for themselves. The presence or absence of new nests is
indicative of good or poor hunting. Often when the squirrels are not
active, hunters shoot into these nests killing many squirrels that are never
retrieved, an atrocious and inexcusable practice.

Emasculation of Young

It is a widespread belief among the people living in eastern Texas that
mature gray squirrels emasculate the young males. The writer, after
examining 269 males, found no evidence of this; however, an occasional
young male was found with one testis atrophied; otherwise no abnormali-
ties of any kind were found. Seton (1928) describes instances in the north
where the botfiy warble (Cuterebra emasculator) had destroyed the testes
of gray squirrels, but he discounts the theory that older males emasculate
the young. The assumption of castration grew out of tales of hunters who
reported finding young without testes. It is easy to get this impression,
for the testes of young squirrels and some adults are slow in descending
from the abdominal cavity into the scrotum. Neither does the adult fox
squirrel castrate young gray squirrels. It is hardly conceivable that an
adult squirrel could dig into the abdominal cavity of the younger animal
and remove the testes. Even so, such action would surely leave a large
scar, but not one scar was found in the 269 males examined.

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS 19

Local Movements and Causes

Abundance of Food in Local Areas. Squirrels congregate in localized
areas when preferred food is abundant. This was well demonstrated on
the Weiser Bottom area in 1936 and 1937. The 1936 census showed a con-
centration of the animals in the western portion of the area whereas in
1937 a great number was seen in the eastern portion about 2 miles distant.
An examination of the two areas revealed that in 1937 acorns of the pin
oak (Quercus phellos) were more numerous in the eastern portion than
in the western. Observers reported the movements of squirrels from one
of these areas to another. A somewhat similar situation existed near
Lufkin, Texas, 0n the Neches River. The pin oak acorn crop failed there,
whereas the shell bark hickory (Hicoria ovata) produced an abundant
crop, hence the squirrels moved in to feed upon the nuts. Cleddie Pate,
of Camden, Texas, reported that squirrels had moved out of one area into
another. Here, too, the squirrels had moved from a location where pin
oak acorns were scarce to one where the acorns of the evergreen oak
(Quercus rhombica) were more plentiful. Evidence was found in each
instance, however, that indicated the main cause for movement was
shortage of food in the area evacuated. Numerous reports of this kind
have come to the writer. None of these movements (locally called migra-
tions) was very extensive, seldom more than 4 or 5 miles.

Because of the diversity and relative abundance of food and cover on
the hammocks the squirrels use these areas more than any other. The
prevalence of flats contiguous to the hammocks enhances the value of the
hammocks as squirrel habitat. In winter the flats lack suitable refuge
cover, but the squirrels make excursions into them in search of food
(mainly elm buds), provided the distance from the hammocks is not too
great. Squirrels utilize the poorly drained habitat principally during the
spring and summer when more food and cover are present. During
winters of normal rainfall the flats are flooded with water, thus pre-
venting the squirrels from securing the acorns or other mast which
would otherwise be available. As the water recedes in late spring the
squirrels move in to feast upon the acorns. Observations indicate that
poorly drained areas are frequented most often when the soil is wet or
damp. No evidence is available that gray squirrels, in sizable numbers,
move into upland areas. Sherman Hubbard cites two instances where
individuals were seen in pine-oak upland approximately 1% miles from
bottomland.

Pecan trees are relatively few in the bottomlands of eastern Texas and
good crops of nuts are fewer still. Yet when good crops are produced
practically all the squirrels in that immediate vicinity congregate and
feed upon them, particularly if cover is nearby.

Elfects of Lakes and Ponds

The spring and summer of 1937 were dry compared with 1936. During
this period, the squirrels were concentrated around lakes, ponds, and

20 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

streams. Since the gray squirrel is less tolerant of drought conditions
than is the fox squirrel, drought is an important factor affecting its abun-
dance in certain areas. Environmental conditions around bodies of water
favor the production of tender buds and twigs on which squirrels feed.
Water for drinking is also available. ‘

Soil

The texture and condition of the soil have much to do with the abundance
and activity of the gray squirrel in a given locality. Throughout this inves-
tigation the writer has been impressed with the amount of ground activity
of these animals and the variation in this activity under different conditions.
If the heavier soils are moist or wet, squirrels will frequent them in search
of food. On the other hand, if they are dry and hard, few squirrels will
be seen there. Since the hammock soils are always soft, greater activity
was noted there than in any other soil type.

Leafing and Flowering of Vegetation

The date of leafing and flowering of forest vegetation influences the
movement of squirrels. In winter squirrels normally are concentrated in
the hammock and transitional types. Along the Trinity River bottom in
1937, it was observed that plants in the poorly drained areas were the
first to begin spring growth and there squirrels were numerous. The early
budding of the elm (Ulmus fulval) was especially evident and observations
and stomach analyses showed that gray squirrels fed upon the buds of
this tree.

Climate As Affecting Squirrel Populations

Rainfall and Drought. Rainfall has great influence upon conditions of
soil and vegetation which in turn may affect the welfare of squirrels. For
instance, in the wet spring of 1936 squirrels fed upon mushrooms which
grew in the damp soil. Early rains, as observed in three different localities
in the late fall of 1937, filled the flats with water,-thus preserving acorns
until late spring, the critical period of acorn shortage. Acorns not flooded
are often destroyed by acorn weevils or eaten by livestock, particularly
hogs.

Droughts decrease the amount of available free water in streams, ponds,
and lakes, causing squirrels to concentrate in small areas where they can
secure water. There they become much more vulnerable to attacks by
man and natural enemies than would otherwise be the case. Periodic rains
cause vegetation to put out new shoots upon which the squirrels feed
whereas drought produces a preponderance of woody stems. Moist soils are
worked extensively by squirrels for the acorns and nuts buried therein.
Dry soils are usually avoided.

Rank vegetation offers better cover for gray squirrels than thin vegeta-
tion. Bottomland vegetation is much more dense during periods of fre-
quent rains than during droughts.

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS 21

Temperature

In the region considered, the pin oak is the key food plant for gray
squirrels, and anything affecting its production of acorns is directly related
to the squirrel population. Vegetation on bottomlands is of course more
subject to frost than that 0n higher ground. This has an effect on the
gray squirrel. For example, in the early spring of 1936 a severe frost
killed a great many pin oak buds, resulting in a small crop of acorns in
1937. T. T. Waddell, State Game Warden, observed that frost also reduced
the acorn crop in southern Texas in 1937. Similarly, heavy ice in mid-
January, 1937, broke off many branches. Two groups of 16 gravid female
squirrels each collected before and after this acorn shortage revealed
average litter sizes of 3 and 2.5 respectively. It is impossible to say Whether
or not the crop shortage had any direct bearing on reduced litter size, but
the census showed a greater population of squirrels "in 1936 than in 1937
in the areas where this acorn shortage occurred (Table 4). Squirrels
have been observed feeding on crustose lichens on tree branches felled
by ice.

Wind

Squirrels abhor wind, especially cold wind, more than any other feature
of Weather or climate. Indeed, prolonged cold, accompanied by Wind, nearly
stops the activity of squirrels. They remain in the den and go hungry
rather than face the Wind. Seton (1928) calls attention to this and gives
instances in the north Where the animal goes into a state of lethargy during
inclement weather. Wind probably decreases the accuracy of jumping as
well as interferes With hearing, thus jeopardizing squirrel security.

The destruction of leaf and twig nests by Wind in the fall and Winter
of 1936 on the study area limited the use of these structures as escape
cover, making the squirrels more vulnerable to hunters and possibly other
enemies. Some residents of southern Texas believe that squirrels move
from areas damaged by hurricanes.

Food Relationships

Feeding Habits. The gray squirrel normally feeds twice a day, begin-
ning early in the morning before daybreak and again in late afternoon
and continuing until after dark. It takes but a short time to appease its
appetite if favorite food is plentiful. Sitting on its haunches, the squirrel
handles its food dextrously With the fore paws. Contrary to popular belief,
little of what the squirrel attempts to eat is wasted. Any animal or bird
that attempts to follow the squirrel to get the crumbs Will find poor pick-
ings. No particular place is selected for eating and if everything goes
well the food usually is consumed on the spot where it is found, Whether
on the ground or in the tree. Once started upon a particular food, it Will
eat its fill. Hawkins (1937), working in Wisconsin, experimented with the
food habits of squirrels and concluded that it takes about 2 pounds of

22 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

food a week or 104 pounds a year for each squirrel. Assuming a population
of one squirrel per acre an idea is gained of how productive an acre of
forest must be to support one animal.

Food Habits as Shown by Stomach Analyses
and Field Observations

Two methods have been employed in studying the food habits, (1)
observations in the field, and (2) analyses of stomach contents. Stomach
analyses have proven far more useful in determining food habits than
have field observations but more analyses are needed to get an adequate
picture. Shyness of the squirrels has made it difficult to make accurate
observations of exactly what they eat in the wild. Even at close range,
with a strong pair of field glasses, it is often impossible to see what
squirrels are actually eating. Over 300 stomachs, mostly from the Trinity
River bottom, have been collected throughout the year. A large sample
of these has been analyzed. Analyses revealed that 59 per cent of all
food eaten was acorns. Other materials present were pecan mast, lepidop-
terous larvae (probably web Worms and tent caterpillars), unidentified
seed, fungi, oak flowers, and unid-entified twig fibers. It appears that gray
squirrels eat a great variety of plant and animal matter other than mast
and lepidopterous larvae, but not in large amounts. Relatively small
amounts of animal food apparently influence breeding. Elmer Bailey of
Livingston, who has been breeding fox squirrels in captivity successfully for
8 years, says that animal food is essential if young squirrels are to be
produced. No other example of fox squirrels breeding in cages has been
found, although many persons keep them in captivity. It is likely that
animal food is essential to the gray squirrel in the wild, for over 3.5
per cent of its total food consists of insects.

The most important mast-bearing trees in the habitat of gray squirrels
in eastern Texas are the oaks (Qae/rcus phellos, Q. nigra, Q. rhombica, Q.
lyrata, Q. alba, and Q. macrocarpal), blackgum (Nyssa aquatica), sweet-
gum (Liquidambar styraciflua), shag bark hickory (Hicoria ovata), beech
(Fagus g1"andifl01'a), and the pecan (Hicoria pecan). The number of gray
squirrels found in an area is likely to be directly proportional to the
abundance of two or more of these species.

Fifteen tree-hole nests known to have been occupied by gray squirrels
contained no cached food. The gray squirrel in eastern Texas apparently
stores its food in the ground and not in trees. The food may or may not
be found later by the same squirrel; in fact, it may not be found at all.
Sixty-six leaf and twig nests also were examined, but none of them con-
tained food. In view of this, the animal must hustle for its food the
entire year. Obviously there is no prolonged hibernation of squirrels in
eastern i Texas.

The gray squirrel begins to eat acorns soon after they begin growth in
the spring and it continues to do so throughout the year if they are

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS 23

available. Indeed, it feeds upon all the fruiting structures and the asso-
ciated parts of the oak trees, including the twigs.

Squirrels dig in the moist earth not only for acorns but also for tender
roots and tubers of many kinds. Ample evidence is at hand to show that
palmetto fruit (Sabal sp.), supplejack (Berchemia scandens), ash buds
(Fraa-itnzts sp.), osage orange (Toocylon pomifera), and many other foods
are also taken. All of these plants contribute to ideal gray squirrel
habitat. Formerly the sweetgum (Liquidambar styraciflua) supplied valu-
able food as well as brood sites, but timber cutting has depleted the stand
in most localities until now it is of secondary importance.

On July 30, 1936, the writer picked up a set of deer antlers that had been
extensively gnawed, evidently by squirrels. Cleddie Pate, of Camden,
actually saw a squirrel in the process of gnawing antlers and he cited
other occasions where antlers had been gnawed. He says green antlers
are preferred to dry ones. Allan (1935) has seen the gray squirrel of
the north gnaw a weathered bone and old tooth marks on the bone indi-
cated that it had been gnawed time after time. Squirrels are also known
to gnaw old turtle shells.

Table 5. Food eaten each month by gray squirrels in eastern Texas

Number
"Month Stomachs Principal Items
Analyzed

January. . . . . 2 Oak mast, pecan mast, lepidopterous larvae.

February. . .. 4 Oak mast and flowers, red haw buds, pecan nuts, lepidopterous
larvae, nematodes*, fungi.

l\Iarch..... . . 5 Oak mast and flowers. wood fragments, lepidopterous larvae,
acorn weevil.

April . . . . . . . . 2 Corm material, oak and pecan mast, unidentified material, ants.

May . . . . . . . . 7 Sedge, oak mast, fungi, Salvia and wood fragments, mulberry
fruit], 3 species of ants, lepidopterous larvae and pupa, 2 species
met es.

June . . . . . . . . 2 Oak mast, fungus, wood fragments, unidentified vegetable matter,
lepidopterous pupa and larvae, wasp larvae, beetle, flesh fly.

July . . . . . . . .. 4 Wild plum, leaf fragments, wood fragments, oak and pecan mast,
lcpidopterous larvae, flies, 3 species ants.

August . . . . .. 6 Compositae seed, unidentified seed fragments, ants, amphibia.

September. . . 11 Grapes, elm, plantain seed, oak mast and buds, pecan kernels, elm
buds, black haw fruit, unidentified seed, grasses, lepidopterous
eggs, adult, unidentified insect larvae.

October. . . . . 4O Oak mast, buds and twigs, unidentified buds, twigs, pecan kernel,
fungi, buds of elm, willow, seeds of yaupon, unidentified roots
and tubers, grapes, Mitchella fruit, buttercup, grass, plantain,
lepidopterous larvae, and traces of 2 additional species.

November. . . 2 Oak, pecan mast, Isoptera. ‘

Decen1ber.... 2 Oak, pecan mast, fungi, mushroom, lepidopterous pupae, insect
larvae.

Total . . . . . . 87

*Probably parasites, not food.
Squirrel Mortality

Predators. Little evidence of predation upon squirrels has been per-
sonally secured. In one instance the writer saw the unsuccessful attempt
of a Cooper hawk to catch a gray squirrel. The hawk made no attempt
to swoop down until the animal was well in the open. Several authentic

24 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

cases are available to show that certain animals and predacious birds do
prey upon squirrels. Among their mammal and bird enemies are the
rattlesnake, chicken snake, coach whip snake, Cooper hawk, marsh hawk,
barred owl, ringtail cat, gray fox, and bobcat. Red~shouldered hawks
and barred owls are very abundant in squirrel territory and probably
are the principal predators, but no evidence is available to prove this.

While general observations indicate that predation upon squirrels in the
wild is not serious, it is obvious that good cover in the form of cavities,
nests, Spanish moss, leaves, and vines is a prerequisite to protection.
Squirrels spend much time on the ground but never far away from suitable
escape cover. Seton (1928), quoting Bachman, says hawks work in pairs
when hunting squirrels. In this manner they are able to catch squirrels
in the trees; otherwise the squirrel can keep turning on the limb and
avoid the talons of a single hawk. While young squirrels are still in the
nest, climbing snakes may do considerable damage to them. Non-climbing
snakes catch squirrels on the ground. On three occasions the timber rattler
has been observed swallowing squirrels.

Parasites

The chigger or redbug (Eutrmnbicula t1‘0]J2'cc¢ Ewing) seems to be the
most serious external parasite of the g'ray squirrel. Fully 75 per cent of
all squirrels killed during the summer were infested with this pest, which
sometimes produced a severe skin irritation. In many instances the
squirrels had scratched the skin raw. Several heavily infested specimens
were in poor physical condition. Few fleas (Orchopeas sp.) are found on
squirrels in summer, but in winter they are quite numerous on certain
individuals. This seasonal fluctuation in the number of fleas seemsto be
correlated with the habits of the squirrels which in winter are more closely
confined to their nests. The largest number of fleas counted on one
squirrel was 18. The American dog tick or wood tick (DCTWZUCGHTOT
variabilis Say) is found on an occasional squirrel but is never numerous.
In some localities, according to H. L. Van Volkenberg of Agricultural and
Mechanical College of Texas, this tick transmits tularaemia and Rocky
Mountain spotted fever.

Stomach nematodes were found in 3 of 87 specimens. Of 2O intestinal
tracts of squirrels examined, 4 contained tapeworms and pinworms.

Disease

Evidence is scarce of sick or diseased squirrels in the wild. Theodore
Turney of Weldon found 5 dead gray squirrels, 3 in 1931 and 2 on March 26,
1938. Apparently these squirrels died of natural causes. The two animals
picked up in 1938 were examined by Dr. Van Volkenberg but no evidence
of disease was found.

Middleton (1930) states that great numbers of gray squirrels were
found dead of some disease in 1923 and 1924 in England. Also he attributes

 

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS 25

the marked fluctuation in squirrel numbers between 1920 and 1926 in
certain localities in England to outbreaks of disease, but he suggests the
possibility that local movements may have been partly responsible.

Modification of Habitat by Man

In a previous paper (1937a), the Writer discussed the efiect on squirrels
of various land use practices. Unlike some of our other Wildlife species,
a suitable habitat for squirrels cannot be produced quickly. Proper use
of the squirrel range by man is absolutely necessary if squirrels are to
be produced in abundance.

Timber Cutting

Unrestricted timber cutting, overgrazing, and drainage all have con-
tributed to the reduction of the number of gray squirrels in eastern Texas,
but timber cutting is the most important. These factors have so altered
the general balance of their habitat that squirrels find some areas no
longer suited to their needs. Optimumlfor gray squirrels is a forest of
bottomland hardwood trees, intermixed with a variety of vines, shrubs, and
herbaceous plants. Fifty per cent hammock, 25 per cent flats, and 25 p-er

Vine Tangle and Other Trees Within Jumping Dis-
Timber cutting and

Fig. 4. A Large Sweetgum with
tance, Making an Ideal Situation for Gray Squirrels.
grazing may eliminate protective cover of this kind.

Photographed by D. W. Lay, March 21, 1937. Texas Cooperative Wildlife Research

Unit No. A881.

26 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

cent well-drained bottomland is ideal. The middle-aged or mature trees
are the most valuable for squirrels because they furnish the most food
and the best brood-rearing sites, as well as opportunities for play and
exercise. These trees are at the height of their seed production and, there-
fore, are important from the standpoint of forest maintenance. Usually
these trees are the ones harvested by the lumber interests. The complete
removal of such timber greatly reduces the value of an area for squirrels.
Hardwood cutting methods, as practiced in eastern Texas, tend to bring
about a second-growth of shrubs and sprouts with an attendant shortage
of seed-bearing trees, conditions that are unfavorable to squirrels.

Obviously, if timber is removed judiciously and selectively, so as to leave
plenty of suitable trees to perpetuate the forest, squirrels and other forest
wildlife will be favored correspondingly. In this instance the best forestry
practices are in accord with the needs of forest game, but hollow trees
should be left for squirrel nests. It is suggested that not more than 30
per cent of the vigorous, middle-aged trees be cut during one operation
and 15 per cent at 10 year intervals thereafter.

Grazing by Livestock

Excessive grazing prevents the reproduction of certain species of plants
that are valuable as food and cover for squirrels, such as mulberry, sweet-
gum, the pin oaks, dogwood, beech, rattan, and some of the grasses and
weeds. On the other hand, moderate grazing by cattle and horses seems
to do little harm and may even prove to be favorable. Squirrels tend to
do more feeding when the herbaceous cover is not too dense. Hogs com-
pete directly with squirrels for mast, particularly for pecans and acorns,
and they should not be tolerated in squirrel habitat.

Drainage

Since flats and ponds are necessary components in ideal gray squirrel
habitat, drainage would naturally lead to a reduction in the number of
squirrels. A good example of this is afforded at Hairy Lake Slough, 18
miles southwest of Trinity. Before drainage, squirrels were abundant
there; now, after drainage, few can be found. Drainage reduces not only
the water supply but the food supply as well. Important acorn and nut
trees such as willow oak, overcup oak, pecan, and other moisture loving
plants, are dependent upon these wet areas. Even if it does not eliminate
these trees altogether, drainage probably reduces the production of their
mast. As a matter of fact, proper distribution of water over the squirrel
range is very important. As previously stated, gray squirrels have a
tendency to concentrate around water and when watering places are limited,
squirrels can be easily found and killed by hunters.

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS 27
ECONOMIC STATUS
Damage to Crops

No damage to crops in eastern Texas by squirrels has come to the
attention of the writer. Old timers in the region, however, have reported
that 30 to 40 years ago they had to watch corn while in the “roasting-ear”
stage to keep squirrels from destroying the crop. J. D. Jowers of Gonzales
related that gray squirrels did considerable damage to pecan orchards in
southern Texas.

Control of Insects

Analyses of 87 gray squirrel stomachs reveal that over 4.5 per cent of the
total food consumed was that of insects, especially members of the order
Lepidoptera. Squirrels may be of some value in keeping these pests under
control; moreover, the good squirrels do in planting acorns and nuts
cannot be overlooked.

Sources of Fur and Food

Although the gray squirrel is hunted most because of its sporting quali-
ties, a number of persons still hunt it for food. No use is made of the
skin as fur and the possibilities of doing so are limited. The hair of the
tail sometimes is used in “camel’s hair” brushes. In summer the pelage
is in poor condition; in Winter the animals are breeding and should not
be disturbed.

Objects of Sport and Monetary Returns

The value of gray squirrels as objects of recreation and sport in eastern
Texas cannot be questioned. As has been pointed out earlier, all classes
of sportsmen pursue squirrels. Deer hunters, failing to bag deer, often
fall back upon the squirrels and no hunting party would be considered
successful unless stewed or fried squirrel was served once during the en-
campment. Many nimrods claim that the squirrel equals the bobwhite
quail in gameness and food qualities. The exercise, sport, and mental stim-
ulation gained from a day in the woods hunting squirrels is the height of
recreation to a great many persons. These qualities place the gray squirrel
high on the game animal list.

Many landowners in eastern Texas lease land for shooting privileges.
In this way they are able to realize a monetary return from the game on
the land. A study of 17 private shooting preserves in six counties has
revealed the fact that 119,190 acres are being utilized for this purpose
(1938). Shooting privileges cost the participants an average of 18.6 cents
an acre. The greatest amount paid was 43 cents an acre and the least
was 1.5 cents. As an economic asset in eastern Texas squirrels compare
favorably with deer and quail.

28 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

Relation to Domestic Animals and Other Wildlife

While squirrels and other wildlife are able to live together without serious
conflict with domestic livestock, there is likely to be rather obvious com-
petition. Hogs consume the mast on which squirrels depend. Cattle, if
over-numerous, eliminate many of the plants that help to make the bottom-
land habitable for squirrels. A few wild species, as bobwhite quail and
jays, consume some acorns. Woodpeckers and crows are reputed to drop
acorns in holes in trees, perhaps in this way helping the squirrel. The
antlers of deer are frequently gnawed by squirrels.

Middleton (1930) reports that in England, where the gray squirrel is
exotic, it preys upon the eggs of 14 different species of wild birds; it is
reputed to have killed adult rabbits. No evidence of squirrels preying
upon birds or other mammals in eastern Texas has come to the attention
of the writer.

HABITAT IMPROVEMENT AND MANAGEMENT PRACTICES
Environmental Control

Squirrel range, like other game environments, can be made to produce a
larger crop of animals by manipulating the habitat. H. H. Chapman (1936)
states that no one need worry about the squirrels. There is no justifica-
tion for this statement, at least in eastern Texas. Events have abundantly
proved that modification of the squirrel’s woodland habitat by man may
be exceedingly detrimental to squirrels. In many localities squirrels have
already decreased alarmingly.

It is a well known principle among biologists that trees which receive
an abundance of sunlight will produce a larger and more frequent seed
crop (mast) than those receiving a limited amount, provided other factors
operate normally. In a forest where dense stands of oaks or other trees
occur, the individual tree finds it difficult or impossible to develop an exten-
sive crown. The lower portion of the existing crown receives a limited
amount of light. The combined effect of these factors prevents the tree
from producing a sizable crop of mast annually. A series of trees grow-
ing in open situations, two each of the red oak, willow oak, and water oak
were observed for a 3 year period. Each year these trees bore a normal
crop of acorns while those in dense forest stands nearby bore a very small
crop or none at all, except for the first year. It has been noted that trees
growing along stream banks and along forest trails consistently yield more
acorns than those in thick stands. Oak trees growing on the hammocks
have less competition for light than those in the poorly drained and ‘Well
drained areas. Their crowns extend above the shrubbery undergrowth and
therefore intercept more light.

By judiciously reducing the competition for light (in selected spots within
dense stands) by taking out a few suppressed and inferior trees the fre-
quency of a normal mast crop might be increased and thereby a foozl
supply for the squirrels insured. Good distribution of food would prevent

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS 29

concentration of squirrels. Wholesale thinning would not be desirable be-
cause such a measure would be too costly and impractical; besides, too
many lumber trees would be lost; moreover, upsetting the ecological suc-
cession to that extent would be risky. This kind of "work is not recom-
mended on a large scale. It is believed that a program of work could be
carried out by landowners and shooting clubs without much cost.

The possibilities should ‘be explored of combining good silviculture with
squirrel management whereby a limited number of mast producing hard-
wood trees could be liberated and brought into greater production, thus con-
tributing both to forest conservation and squirrel increase.

Creation of Ponds

The creation of ponds by throwing up narrow earthen dikes along the
sloughs, creeks, and flats in favorable areas over the range of gray squirrels
may increase the carrying capacity of such areas. It is possible that such
a procedure would lessen the concentration of gray squirrels around exist-
ing ponds as well as induce the growth of additional desirable vegeta-
tion. More important than the creation of new ponds is the preservation
of existing ones. Drainage projects should be avoided in good squirrel
habitat, if one wishes to favor the squirrel.

In some localities, especially in parks, the number of nesting holes limit
the production of squirrels. Waterproof nest boxes may be installed in
places of this kind for use by squirrels. Natural hollow logs are best
for this purpose.

Efiect of Hunting

The effect of hunting on the gray squirrel population is shown in Table 6.
The areas considered are adjacent and almost identical in habitat values.
The difference in population density is attributed largely if not solely to
hunting. The Prison System Pasture is typical of eastern Texas with
respect to hunting pressure. The influx of squirrels from the Weiser Bottom
Game Preserve has not been determined, but it is probable that individuals
from the Game Preserve have helped to keep the population from decreas-
ing still further in the Prison Pasture. In spite of this, according to sports-

Table 6. Comparison of gray squirrel population density on protected
and unprotected areas

1 Total Number
Squirrel Squirrels

Locality t Condition Acreage

k ‘Population Per Acre

l

l .
l

“riser Bottom Game Preserve.

_ Protected from
Houston and \Valker Counties

hunting 7,000 7,770 1.11

 

Prison System Pasture. Houston and iNot protected
Walker Counties from hunting l 2,000 620 .31

30 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

men and our own counts, the population there is decreasing steadily. In
order to maintain the population here hunting pressure must be cut down.
The figures also show that the fox squirrel is slightly more able to main-
tain its numbers under hunting pressure than is the gray. The reasons for
this have not been satisfactorily determined. It is suggested that ease of
finding the gray and the ability of the fox to escape danger are con-
tributing factors. Also, heavy timber cutting has made the area more de-
sirable for fox squirrels, for the latter favors a more open habitat than
does the gray squirrel.

Sportsmen in other sections have reported that the fox squirrel is invad-
ing the gray’s habitat and they point out that more fox squirrels are now
killed than formerly. This is probably attributable to the decrease in
number of gray squirrels. Few data are available on the inter-relationship
of the two species. More study is necessary before conclusions can be drawn,
or fully satisfactory principles of squirrel management established.

SQUIRRELS AND THE TEXAS GAME LAWS

Of major importance in gray squirrel management are the shooting regu-
lations affecting the counties of eastern Texas. A review of the various
county laws has revealed the fact that each of the 47 counties has an open
shooting season during one of the two annual breeding periods of the
species. Although complete information concerning the breeding cycles is
not at hand, available data indicate the inadequacy of present shooting reg-
ulations. A record of 135 sexually mature females places the principal
breeding season during the periods June 1 to October 15 and December 1
to April 30 of each year. Of the 47 counties, 35 have open season in
July; 35 are open during all of October and December; 8 allow hunting
in January.

With the present knowledge of breeding habits, an open season is recom-
mended for the period October 15 to December 15. If desired, another
season may be allowed between May 1 and May 15. The present bag limit
of 10 should be reduced to 5. The shooting regulations should be flexible
so that they may correspond with fluctuations in the population and
breeding periods. '

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS

31

GRAY AND FOX SQUIRREL LAWS

COUNTIES

I939—I94I

_SOLID BARS INDICATE OPEN SEASON ON SQUIRRELS
JULY
::=IiII=====H

DAILY
BAG
LIMIT

MAR.

F

ANGELINA

IN EASTERN TEXAS

WEEKLY
SAG
LIMIT

POSSESSION
LIMIT

IO

NONE

2O

CHEROKEE

IO

2O

HARDIN
LIBERTY

2O

JASPER
NEWTON

2O

JEFFERSON

NACOGDOCHES

POLK, SHELBY
TRINITY, TYLER

SABINE
SAN AUGUSTINE

SAN JACINTO

WOOD

I5

2O

FRANKLIN, DELTA
RED RIVER, HOPKINS

GALVESTON , LAMAR

CHAMBERS

ANDERSON, SMITH
VAN ZANDT, sown:
FANNIN, GREGG
HARRISON, HUNT
HENDERSON, RUSK
MORRIS, HOUSTON
TITUS, PANOLA
MONTGOMERY, CASS
UPSHUR, RAINS
CAMP, ORANGE
MARION, HARRIS
KAUFMAN, WALKER

WIDTH OF LINE
SHOWS EXTENT
OF BREEDING

NO

 

I
WINTER

2O

2O

2O

2O

2O

BAG LIMITS

2O

BASED
ON A SURVEY OF I35

GR AY SQUIRRELS

Fig. 5. Table of Squirrel Laws.

32 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

ACKNOWLEDGMENTS

In the preparation of this paper, the Writer is grateful for suggestions
and help from Drs. W. P. Taylor and W. B. Davis of the Texas Cooperative
Wildlife Research Unit, both of whom read and revised the manuscript
and offered pertinent suggestions. To Director E. O. Siecke of the Texas
Forest Service, special thanks are due for making available an assistant,
William Davis, a former enrollee in the Civilian Conservation Corps, who
helped with the field work.

SUMMARY AND CONCLUSIONS

1. The gray squirrel is one of the most important game species in eastern
Texas where it is becoming fewer in number each year.

2. The best methods of estimating squirrel abundance, in order of their
effectiveness, are (1) time-area count, (2) leaf and twig nest count,
(3) hunting with a dog. '

3. Counting leaf and twig nests is the quickest way of estimating a gray
squirrel population. A close correlation exists between squirrel
density and squirrel nests in late summer or in the fall, there being
about one nest to every two squirrels.

4. Three types of gray squirrel habitat are recognized in eastern Texas.
In order of their carrying capacity they are (1) hammocks or low
sandy loam ridges along flood plains, (2) poorly drained bottomland,
(3) well drained bottomland.

5. In the two years of study, gray squirrels have been found to fluctuate
in number. The census taken on 7,000 acres showed a reduction of
13.8 per cent between 1936 and 1937. Scarcity of pin oak acorns
(Q. phellos and Q. nigra) probably accounts in large part for this
decrease. No evidence has been found that gray squirrels migrate.
Local movements are often misleading in this regard.

6. Under present conditions a density of slightly more than one squirrel
to the acre may be expected in better than average habitat protected
from shooting. Hunting pressure in certain selected areas in eastern
Texas has cut down the population density to about one squirrel
to every three acres. Management may considerably increase the
possibilities of squirrel production.

7. In contrast to the fox squirrel, the gray squirrel has two well defined
periods of activity, (1) very early morning and (2) late afternoon.
Warm summer rains favor activity of gray squirrels.

8. In autumn and spring the gray squirrel population shifts about some-
what. At other times it is more or less sedentary. The cruising
radius of individual squirrels is about 200 yards.

9. Two breeding seasons are evident in eastern Texas, one in winter and
one in summer. The winter peak is reached about the latter part
of January and the summer peak in August.

10. Young gray squirrels remain in vulnerable family groups for about
4% months.

11.

12.

13.

14.

15.

16.

fl_‘\
x17.

18.

19.

20.
21.

22.
23.

24.

A POPULATION STUDY OF THE GRAY SQUIRREL IN EASTERN TEXAS 33

The gray squirrel is nervous, a characteristic that makes it a superior
game animal, but often betrays it to the hunter. Gray squirrels are
easier t0 locate than fox squirrels.

N0 evidence is available to substantiate the claim that gray squirrels
emasculate each other or that the young gray is castrated by adult
fox squirrels.

Unrestricted timber cutting, overgrazing, and drainage have contributed
to the reduction of gray squirrels. Unrestricted timber cutting re-
moves the most desirable trees from the standpoint of seed produc-
tion and breeding sites of squirrels. Excessive grazing prevents
reproduction of species valuable as food and cover. Drainage reduces
the water supply and acts unfavorably upon water-loving species of
plants valuable to squirrels.

Abundance of food in particular places causes local movements of
squirrels. Conditions of soil, vegetation, and distribution of ponds
and lakes also have much to do with the phenomenon.

Low temperature and wind affect the activity of squirrels to a marked
degree. Frost or extreme cold has a detrimental effect upon vegeta-
tion, thereby reducing the mast crop. Wind destroys many leaf and
twig nests, which could otherwise be used as refuge places. Wind
also virtually prevents squirrel activity in seeking food.

Pin oak acorns (Quercus phellos and Q. nigrcz) constituted 59 per cent
of the total food consumed by 87 gray squirrels. A great variety
of other foods, including insects, were taken.

The most important mast bearing trees in eastern Texas gray squirrel
habitat are oaks (Quercus phellos, Q. nigra, Q. rhombrica, Q. lyratai,
Q. alba, and Q. macrocarpa), blackgum (Nyssa sylvatica), shag bark
hickory (Hicoria ovata), beech (Fagus grandiflora), pecan (Hiicorict
pecan), sweetgum (Liquidambar styraciflua).

The extent of damage done to squirrels through natural predation is
unknown. Hawks, snakes, gray fox, ringtail cat, and bobcat have
been known to prey upon gray squirrels. Seemingly predation is
less important in limiting squirrel numbers than are habitat changes
and overhunting.

The most common external parasites found on squirrels are chiggers
and fleas; the most abundant internal parasite is the tapeworm.

Positive evidence of disease among gray squirrels is lacking.

At the present time squirrels do practically no damage to crops in
eastern Texas.

Squirrels ofler substantial values from an aesthetic standpoint.

Gray squirrels live in apparent harmony with most other species
of wildlife.

Manipulation of squirrel habitat should improve conditions for squir-
rels. Release cutting of key mast trees and creation of ponds should
bring about a more frequent mast crop and a better distribution of
food and water for squirrels. Careful regulation of grazing so ‘that

34 BULLETIN NO. 591, TEXAS AGRICULTURAL EXPERIMENT STATION

overgrazing might be eliminated, would also help. Provision of nest
boxes, in parks and other areas where maximum populations are
desired, may be recommended. Under proper management, the
squirrel population of eastern Texas could be approximately doubled.
25. Squirrel shooting seasons in eastern Texas are open during the breed-
ing periods of the animals. A revision of the squirrel laws is needed.

LITERATURE CITED

Allan, Philip F. 1935. Bone cache of a gray squirrel. Journal of Mammalogy 16:326.

Chapman, F. B. 1936. Fox squirrels and gray squirrels. Ohio Division Conservation
Bulletin 127 (mimeographed).

Chapman, F. B. 1937. Controlled squirrel and rabbit hunting on state hunting preserves,
1936. Ohio Wildlife Research Station, Release 37 (mimeographed).

Chapman, F. B. 1938a. Controlled squirrel hunting on Ohio preserves, 1937. Ohio Wildlife
Research Station, Release 68, 8 pp. (mimeographed).

Chapman, F. B. 1938b. A summary of the Ohio gray squirrel investigation. Ohio Wildlife
Research Station, Release 71, 8 pp. (mimeographed).

Chapman, H. H. 1936. Forestry and game management. Journal of Forestry 34:104-106.

Dice, L. R. 1931. Methods of indicating abundance of mammals. Journal of Mammalogy
12:376-381.

Deansely, Ruth, and Parkes, A. S. 1932. The oestrus cycle of the gray squirrel. Phil.
Trans. Royal Society of London, Parts IV and V.

Edminster, F. C. 1937. The gray squirrel migration. Nature Magazine, May 1934, pp.
221-222, 225, 256.

Goodrum, Phil D. 1937a. Wise use of forested land necessary for squirrel conservation in
eastern Texas. Progress Report, Texas Agricultural Experiment Station, Division
of Wildlife Research, 4 pp. (mimeographed).

Goodrum, Phil D. 1937b. Notes on the gray and fox squirrel of eastern Texas. Trans.
Second North American Wildlife Conference, pp. 499-504.

Goodrum, Phil D. 1938. Squirrel management in east Texas. Trans. Third North Ameri-
can Wildlife Conference, pp. 670-676.

Goodwin, George G. 1934. The gray squirrel migration. Nature Magazine, May 1934.
pp. 221-222, 255-256.

Hflwkiilgsxigagé 1937. Winter feeding at Faville Grove, 1935-1936. Am. Midland Nat.

Hibbard, Claude W. 1935. Breeding season of gray squirrel and flying squirrel. Journal
of Mammalogy 16:325-326.

Jackson, H. H. T. 1921. A recent migration of the gray squirrel in Wisconsin. Journal
of Mammalogy 2:113-114.

Leopold, Aldo. 1933. Game management. New York: Scribners, 481 pp.

Middleton, A. D. 1930. The ecology of the American gray squirrel (Sciurus carolinensis
Gmelin) in the British Isles. Proc. Zool. Soc., London, Part III, pp. 809-843.

Parsons, R. T. and Middleton, A. D. 1937. Distribution of the gray squirrel. Journal of
Ecology, London, pp. 286-290.

Seton, E. T. 1928. Lives of game animals. New York: Doubleday Doran, Vol. IV,
Rodents, 949 pp.

Wight, H. M. 1931. Wildlife reconnaissance. Trans. 18th Am. Game Conference, pp. 203-213.

Wight, H. M. 1934. The cover map and game census in pheasant management. Trans. 20th
Am. Game Conference, pp. 329-333.