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TREE SQUIRRELS

Jeffrey J. Jackson

Extension Wildlife Specialist

Warnell School of Forest Resources

University of Georgia

Athens, Georgia 30602

Fig. 1. Fox squirrel, Sciurus niger

Damage Prevention and

Control Methods

Exclusion

Install sheet metal bands on isolated

trees to prevent damage to

developing nuts.

Close external openings to buildings to

stop damage to building interiors.

Place an 18-inch (46-cm) section of

4-inch (10-cm) diameter plastic pipe

or a one-way door over openings to

allow squirrels to leave and p revent

them from returning.

Plastic tubes on wires may prevent

access to buildings.

Cultural Methods

Remove selected trees or their

branches to prevent access to

structures.

Repellents

Naphthalene (moth balls), Ro-pel,

capsaicin, and polybutenes are

registered for controlling tree

squirrels.

Toxicants

None are registered.

Fumigants

None are registered.

Trapping

Leghold trap s.

Box and cage traps.

Rat snap traps.

Box choker traps.

Shooting

Effective where firearms are permit-

ted. Use a shotgun with No. 6 shot

or a .22-caliber rifle.

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994

Coop erat ive Extension Division

Institute of Agriculture and Natural Resources

University of Nebraska - Lincoln

United States Department of Agriculture

Animal and Plant Health Inspection Service

Animal Damage Control

Great Plains Agricultural Council

Wildlife Committee

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Identification

In this chapter tree squirrels are

divided into three groups: large tree

squirrels, pine squirrels, and flying

squirrels. Large tree squirrels include

fox (Sciurus niger), eastern gray (Sciurus

carolinensis), western gray (Sciurus

griseus), and tassel-eared (Sciurus

aberti) squirrels.

Fox squirrels (Fig. 1) measure 18 to 27

inches (46 to 69 cm) from nose to tip of

tail. They weigh about 1 3/4 pounds

(787 g) to 2 1/4 pounds (1,012 g). Color

varies greatly, from all black in Florida

to silver gray with a white belly in

Maryland. Georgia fox squirrels usu-

ally have a black face. Ohio and Michi-

gan fox squirrels are grizzled

gray-brown above with an orange

underside. Sometimes several color

variations occur in a single population.

Eastern gray squirrels are also variable

in color. Some have a distinct reddish

cast to their gray coat. Black ones are

common in some northern parts of

their range. Eastern gray squirrels

measure 16 to 20 inches (41 to 51 cm).

They weigh from 1 1/4 pounds (567 g)

to 1 3/4 pounds (794 g).

The western gray squirrel is gray

above with sharply distinct white

underparts. Size is similar to that of

the eastern gray squirrel.

Tassel-eared squirrels are similar in

size to gray squirrels and have several

color phases. The most common is

gray above with a broad reddish band

down the back. Black tufted ears are

their most distinguishing characteristic

(the tufts are larger in winter, about 1

inch [2.5 cm]).

There are two species of pine squirrels:

the red squirrel (Tamiasciurus

hudsonicus) and Douglas pine squirrel

(Tamiasciurus douglasii). Pine squirrels

are 10 to 15 inches (25 to 38 cm) in total

length and weigh 1/3 to 2/3 pounds

(151 to 303 g). Red squirrels are red-

brown above with white underparts.

Douglas squirrels are gray-brown

above with yellowish underparts. Both

species have small ear tufts and often

have a black stripe separating the dark

up per color from the light belly.

where they have been introduced

(Fig. 2).

Eastern gray squirrels have a similar

range to that of fox squirrels but do

not occur in many western areas of the

fox squirrel’s range. They have been

introduced in several locations in the

West (Fig. 3).

Western gray squirrels are confined to

west coast states and a small portion of

western Nevada (Fig. 3).

Pine squirrels occur across northern

North America south into the Appala-

chians and Rockies, and on the west

coast.

Red squirrels are often associated with

coniferous forests. The Douglas squir-

rel is restricted to the west coast from

southwestern British Columbia south

through the S ierras to northern Baja

California (Fig. 4).

Fig. 2. Range of the fox squirrel (dark) and

tassel-eared squirrel (light) in North America.

Fig. 3. Range of the eastern gray squirrel (dark)

and western gray squirrel (light) in North

America.

Fig. 4. Range of the red squirrel (dark) and

Douglas squirrel (light) in North America.

Fig. 5. Range of the northern flying squirrel

(dark) and southern flying squirrel (light) in

No rth America.

Two species of flying squirrels occur in

North America. The southern flying

squirrel (Glaucomys volans) is 8 to 10

inches (20 to 25 cm) long. The northern

flying squirrel (Glaucomys sabrinus)

averages 2 inches (5 cm) longer. It can

be difficult to distinguish between the

two; both may be various shades of

gray or brown above and lighter

below. A sharp line of demarcation

separates the darker upper color from

the lighter belly. The most distinctive

characteristics of flying squirrels are

the broad webs of skin connecting the

fore and hind legs at the wrists, and

the distinctly flattened tail.

Range

Fox squirrels occur in much of the

eastern and central United States, as

well as in several locations in the West,

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The tassel-eared squirrel is restricted

to Ponderosa pine forests in the South-

west, usually at altitudes above 5,000

feet (1,500 m). It occurs in portions of

Wyoming, Colorado, New Mexico,

Arizona, and Utah (Fig. 2).

The northern flying squirrel occurs

across northern North America. Its

range extends south into the Appala-

chians and Rockies. The southern fly-

ing squirrel occ urs in the central and

eastern United States (Fig. 5).

Habitat

Fox squirrels and gray squirrels

inhabit the same kinds of forests, both

hardwood and coniferous, over much

of their range. Gray squirrels are more

abundant where a high percentage of

land is forested. In areas with 10% for-

est cover, fox and gray squirrel popu-

lations may be equal. Fox squirrels

prefer oak-hickory habitat over much

of their range, especially in the West.

In Georgia and Florida, fox squirrels

seem to prefer pine timber. The west-

ern gray squirrel prefers mixed hard-

woods and conifers and dry open

hardwoods. Tassel-eared squirrels are

strongly associated with Ponderosa

pine. Pine squirrels prefer coniferous

forests but also occur in mixed conifer

and hardwood forests, or sometimes

in hardwood habitats.

Food Habits

Fox and gray squirrels have similar

food habits. They will eat a great vari-

ety of native foods and adapt quickly

to unusual food sources. Typically,

they feed on mast (wild tree fruits and

nuts) in fall and early winter. Acorns,

hickory nuts, walnuts, and osage

orange fruits are favorite fall foods.

Nuts are often cached for later use. In

late winter and early spring they pre-

fer tree buds. In summer they eat

fruits, berries, and succulent plant

materials. Fungi, corn, and cultivated

fruits are taken when available. During

population peaks, when food is scarce,

these squirrels may chew bark from a

variety of trees. They will also eat

insects and other animal matter.

Pine squirrels are often heavily depen-

dent on coniferous forests for cones

and buds but will also eat a variety of

other foods common to gray and fox

squirrel diets. Douglas squirrels

depend largely on Ponderosa pine for

food. Flying squirrels’ food habits are

generally similar to those of other

squirrels. However, they are the most

carnivorous of all tree squirrels. They

eat bird eggs and nestlings, insects,

and other animal matter when avail-

able. Flying squirrels often occupy bird

houses, esp ecially bluebird houses.

General Biology,

Reproduction, and

Behavior

Fox and gray squirrels breed when

they are 1 year old. They breed in mid-

December or early January and again

in June. Young squirrels may breed

only once in their first year. The gesta-

tion period is 42 to 45 days.

During the breeding season, noisy

mating chases take place when one or

more males pursue a female through

the trees.

They nest in tree cavities, human-

made squirrel boxes, or in leaf nests.

Leaf nests are constructed with a

frame of sticks filled with dry leaves

and lined with leaves, strips of bark,

corn husks, or other materials. Sur-

vival of young in cavities is higher

than in leaf nests. Cavities are the pre-

ferred nest sites.

About 3 young comprise a litter. At

birth they are hairless, blind, and their

ears are closed. Newborns weigh

about 1/2 ounce (14 g) at birth and 3 to

4 ounces (84 to 112 g) at 5 weeks.

Young begin to explore outside the

nest about the time they are weaned at

10 to 12 weeks. At weaning they are

about half of their adult weight.

Home range size depends on the sea-

son and availability of food. It may

vary from 1 to 100 acres (0.4 to 40 ha).

Squirrels move within their range

according to availability of food. They

often seek mast-bearing forests in fall

and favor tender buds in elm and

maple forests in the spring.

During fall, squirrels may travel 50

miles (80 km) or more in search of bet-

ter habitat. Squirrel populations peri-

odically rise and fall. During periods

of high populations, squirrels—espe-

cially gray squirrels—may go on mass

emigrations. At such times many

animals die.

Fox and gray squirrels are vulnerable

to numerous parasites and diseases.

Ticks, mange mites, fleas, and internal

parasites are common. S quirrel hunt-

ers often notice bot fly larvae (called

“wolves” or “warbles”) protruding

from the skin. These fly larvae do not

impair the quality of the meat for

eating.

Squirrels are a food source for hawks,

owls, snakes, and several mammalian

predators. Predation seems to have

little effect on squirrel populations.

Typically about half the squirrels in a

population die each year. In the wild,

squirrels over 4 years old are rare,

while in captivity individuals may live

10 years or more.

The biology of other North American

squirrels has much in common with

that of fox and gray squirrels, although

most other species have one breeding

season per year. Flying squirrels are

unique in that they are active at night.

All other species are active during the

day.

Damage

Squirrels may occasionally damage

forest trees by chewing bark from

branches and trunks. Pine squirrels

damage Ponderosa pine, jack pine,

and paper birch. In the Southeast, fox

squirrels damage loblolly and other

pines.

These species and others may eat

cones and nip twigs to the extent that

they interfere with natural reseeding of

important forest trees. This is a par-

ticular problem in Ponderosa pine

forests where pine squirrels may

remove 60% to 80% of the cones in

poor to fair seed years. In forest seed

orchards, such squirrel damage

interferes with commercial seed

production.

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In nut orchards, squirrels can severely

curtail production by eating nuts pre-

maturely and by carrying off mature

nuts. In New England fruit orchards,

pine squirrels may eat ovaries of

cherry blossoms and destroy ripe

pears. Pine, gray, and fox squirrels

may chew bark of various orchard

trees.

In residential areas, squirrels some-

times travel powerlines and short out

transformers. They gnaw on wires,

enter buildings, and build nests in

attics. They frequently chew holes

through pipelines used in maple syrup

production.

Squirrels occasionally damage lawns

by burying or searching for and dig-

ging up nuts. They will chew bark and

clip twigs on ornamental trees or

shrubbery planted in yards. Often

squirrels take food at feeders intended

for birds. Sometimes they chew to

enlarge openings of bird houses and

then enter to eat nestling songbirds.

Flying squirrels are small enough to

enter most bird houses and are espe-

cially likely to eat nesting birds.

In gardens, squirrels may eat planted

seeds, mature fruits, or grains such as

corn.

Legal Status

Fox and gray squirrels are usually clas-

sified as game animals in states where

they occur. The tassel-eared squirrel is

normally a protected species. Check

with local or state authorities to deter-

mine legal status of squirrels in your

area.

Damage Prevention and

Control Methods

Exclusion

Prevent squirrels from climbing iso-

lated trees and power poles by encir-

cling them with a 2-foot-wide (61-cm)

collar of metal 6 feet (1.8 m) off the

ground. Attach metal using encircling

wires held together with springs to

allow for tree growth.

Prevent squirrels from traveling on

wires by installing 2-foot (61-cm) sec-

tions of lightweight 2- to 3-inch diam-

eter (5.1- to 7.6-cm) plastic pipe. Slit

the pipe lengthwise, sp read it open,

and place it over the wire. The pipe

will rotate on the wire and cause trav-

eling squirrels to tumble.

Close openings to attics and other

parts of buildings but make sure not to

lock squirrels inside. They may cause a

great deal of damage in their efforts to

chew out. Place traps inside as a pre-

caution after openings are closed. A

squirrel excluder can be improvised by

mounting an 18-inch (46-c m) section of

4-inch (10-cm) plastic pipe over an

opening. The pipe should point down

at a 45

o

angle. A one-way door can also

be used over an opening to let squir-

rels out and prevent them from return-

ing.

Close openings to buildings with

heavy 1/2-inch (1.3-cm) wire mesh or

make other suitable repairs.

Custom-designed wire mesh fences

topped with electrified wires may

effectively keep out squirrels out of

gardens or small orchards.

Habitat Modification

Trim limbs and trees to 6 to 8 feet (1.8

to 2.4 m) away from buildings to pre-

vent squirrels from jumping onto

roofs.

In backyards where squirrels are

causing problems at bird feeders,

consider providing an alternative

food source. Wire or nail an ear of corn

to a tree or wooden fence post away

from where the squirrels are causing

problems.

In high-value crop situations, it may

pay to remove woods or other trees

near orchards to block the “squirrel

highway.”

Repellents

Naphthalene (moth balls) may temp o-

rarily discourage squirrels from enter-

ing attics and other enclosed spaces.

Use of naphthalene in attics of occu-

pied buildings is not recommended,

however, because it can cause severe

distress to people. Supplement this

method with lights. A cat in the attic

may discourage squirrels.

Ro-pel is a taste repellent that can be

applied to seeds, bulbs, and flowers;

trees and shrubs; poles and fences; sid-

ing and outdoor furniture. Capsaicin is

also a taste repellent, registered for use

on maple sap collecting equipment.

Polybutenes are sticky materials that

can be applied to buildings, railings,

downspouts, and other areas to keep

squirrels from climbing. They can be

messy. A preapplication of masking

tape is recommended.

Toxicants

None are registered.

Fumigants

None are registered.

Trapping

A variety of traps will catch squirrels,

including No. 0 or No. 1 leghold traps,

the “Better Squirrel and Rat Trap,” box

traps, and cage traps. Regular rat-sized

snap trap s will catch flying squirrels

and small pine squirrels. Glue traps for

rats will catch small squirrels.

Since squirrels are classified as game

species in most states, trapping per-

mits may be required from your local

state wildlife agency or municipal Ani-

mal Control office. Wire cage traps

and box traps can be used to capture

squirrels alive. Tie trap doors open for

2 to 3 days to get squirrels accustomed

to feeding in the traps. Then set the

traps and check them twice daily.

Inform your neighbors of your trap-

ping activities. Translocation of tree

squirrels is a questionable practice

because of the stress placed on trans-

ported and resident squirrels and con-

cerns regarding the transmission of

diseases.

Good baits are slices of orange and

apple, walnuts or pecans removed

from the shell, and peanut butter.

Other foods familiar to the squirrel

may also work well, such as corn or

sunflower seeds.

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Shooting

Where firearms are permitted, shoot-

ing is effective. A shotgun with No. 6

shot or a .22-caliber rifle is suitable.

Check with your state wildlife agency

for regulations pertaining to the spe-

cies in your area.

Other Methods

Often several control methods used

simultaneously are more successful

than a single method. For example, to

remove a squirrel from an attic, watch

squirrels to determine where they

enter. Then use repellents and lights to

drive them out. After squirrels ap pear

to have left the building, use appropri-

ate exclusion methods to keep them

out. One or more baited traps will

catch squirrels that are accidentally

closed in. This last step is very impor-

tant because locked-in squirrels may

cause damage when they try to chew

their way out.

Squirrel damage in yards, gardens,

forests, and orchards is often very dif-

ficult to control. During population

highs, new squirrels arrive quickly to

replace those shot or trapped.

Economics of Damage

and Control

Squirrels cause economic losses to

homeowners, nu t growers, and forest

managers. The extent of these losses is

not well known.

Squirrels caused 177 power outages in

Lincoln, Nebraska, in 1980, which was

24% of all outages. Estimated annual

costs were $23,364 for repairs, public

relations, and lost revenue. In Omaha,

in 1985, squirrels caused 332 outages

costing at least $47,144. After squirrel

guards were installed over pole-

mounted transformers in Lincoln in

1985, annual costs were reduced 78%

to $5,148.

Acknowledgments

References by Boggess (1980) and Flyger and

Gates (1982a,b) were particularly useful in

preparing this publication. The manuscript

was read and improved by the comments of

Elizabeth McGhee.

Figure 1 from Schwartz and Schwartz (1981).

Figures 2 through 4 adapted from Flyger and

Gates (1982a,b) by Jill Sack Johnson.

Figure 5 adapted from Burt and Grossenheider

(1976) by David Thornhill.

For Additional

Information

Baumgartner, L. L. 1940. Trapping, handling

and marking fo x squirrels. J. Wildl. Manage.

4:444-450.

Boggess, E. K. 1980. Tree squirrels. in F. R.

Henderson, ed. Prevention and contro l of

wildlife damage. Great Plains Agric. Council

and Kansas Coop. Ext. Serv. Kansas State

Univ., Manhattan.

Burt, W. H., and R. P. Grossenheider. 1976. A

field guide to the mammals, 3d ed.

Houghton Mifflin Co. Boston. 289 pp.

Daviso n, V. E. 1964. Selection of foo ds by gray

squirrels. J. Wildl. Manage. 28:346-352.

Dolan, P. G., and D. C. Carter. 1977. Glaucomys

volans. Mammal. Species 78:1-6.

Flyger, V., and J. E. Gates. 1982a. Fox and gray

squirrels. Pages 209-229 in J. A. Chapman

and G. A. Feldhamer, eds. Wild mammals of

North Americ a: biology, management, and

economics. The Johns Hopkins Univ. Press,

Baltimore.

Flyger, V., and J. E. Gates. 1982b. Pine squirrels.

Pages 230-238 in J. A. Chapman and G. A.

Feldhamer, eds. Wild mammals of North

America: biolo gy, management, and

economics. The Johns Hopkins Univ. Press,

Baltimore.

Hall, R. E., and K. R. Kelson. 1959. The

mammals of North America, Vol. 1. The

Ronald Press Co., New York. 546 pp.

Hamilton, J. C., R. J. Johnson, R. M. Case, and M.

W. Riley. 1988. Assessment of squirrel-

caused power outages. Vertebr. Pest Control

Manage. Mater. 6:34-41.

Madson, J. 1964. Gray and fo x squirrels. Olin

Mathieson Chem. Corp. East Alton, Illinois.

112 pp.

Nash, D. J., and R. N. Seaman. 1977. Sciurus

aberti. Mammal. Species 80:1-5.

National Pest C ontrol Associatio n. 1964. Tree

squirrels—a fact sheet. Nat. Pest C ontrol

Assoc. Tech. Release 20-64.

Schwartz, C. W., and E. R. Schwartz. 1981. The

wild mammals of Missouri, rev. ed. Univ.

Missouri Press, Columbia. 356 pp.

Editors

Scott E. Hygnstrom

Robert M. Timm

Gary E. Larson

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