RODENTS: Squirrels, Thirteen-Lined Ground
Thirteen-lined ground squirrel, Spermophilus
tridecemlineatus (formerly citellus spp.)
Damage Prevention and Control
Buried galvanized hardware cloth is effective, but
Destroy burrows and habitat by deep soil tillage.
Allow growth of tall rank vegetation.
Plant as early as conditions permit before squirrels
emerge from hibernation.
Provide alternative foods in minimum-tillage fields.
None are registered.
Wooden-base rat-sized snap traps.
Leghold and body-gripping traps.
Effective if persistent.
The thirteen-lined ground
squirrel (Fig. 1) is a slender rat-sized rodent weighing
about 8 ounces (227 g) with a length of about 10 inches
(25 cm) including a tail of 3 inches (8 cm). As its name
implies, 13 stripes run the length of this ground
squirrel’s body. Five of the light-colored lines break
up into a series of spots as they progress down the back
and over the rump. Five light and four dark stripes
extend along the top of the head and end between the
animal’s eyes. The cheeks, sides of the body, and legs
are yellowish, tan, or tan with an orange cast. The
chest and belly are thinly covered with light tan fur.
Each front foot has four toes with long slender digging
claws. There are five toes on each hind foot. Some of
the common or colloquial names for this species include
“thirteen-liners,” “stripers,” “striped ground
squirrels,” “striped gophers,” and “gophers.”
The thirteen-lined ground
squirrel is a grassland animal. Its original range was
limited to the prairies of the North American Great
Plains. When Europeans arrived and started clearing
forests and establishing pastures, the thirteen-lined
ground squirrel was quick to extend its range into the
new habitat. Today, it ranges from central Alberta,
Manitoba, and Saskatchewan in the north to Texas and New
Mexico in the south, and from central Ohio in the east
to Colorado in the west (Fig. 2). The forests of the
Appalachian Highlands and the Rocky Mountains have
halted their east/west range expansion. There are a few
colonies in Venango County, Pennsylvania, the result of
introductions made in 1919.
squirrels are omnivorous. At least 50% of their diet is
animal matter — grasshoppers, wireworms, caterpillars,
beetles, cutworms, ants, insect eggs, mice, earthworms,
small birds, and each other. The vegetative portion of
the diet includes seeds, green shoots, flower heads,
roots, vegetables, fruits, and cereal grains. They
rarely drink water, depending instead on water contained
in their food. They cache large quantities of seeds and
grass, but never meat. The cached food may be eaten
during periods of bad weather or in the late autumn and
early spring when other food is scarce.
General Biology, Reproduction, and Behavior
squirrels are strictly diurnal, coming above ground when
the sun is high and the earth is warm, and returning to
the warmth and safety of their burrows long before
sundown. They rarely venture out of the burrow on damp,
dark, or overcast days. When they venture out, they will
often stand upright, with front paws held close to the
chest, surveying their domain. If danger threatens, they
run, with tail held horizontally, to the nearest burrow.
The inconspicuous 2-inch (5-cm) diameter burrow opening
is often concealed by vegetation and rarely has soil
scattered in front of it like a woodchuck’s burrow. The
main entrance plunges down 6 inches (15 cm) or more
before angling off into a complex system of galleries
and side entranceways. The nesting chamber, about 9
inches (23 cm) in diameter and lined with fine dry
grass, is located somewhat deeper than the main burrow
system. The thirteen-lined ground squirrel’s natural
enemies include just about all predators, especially
hawks, badgers, weasels, foxes, coyotes, bull snakes,
and black snakes.
squirrels begin hibernation in September or early
October and emerge between late March and early May in
the northern portions of their range. In southern Texas,
they have been observed above ground as late as October
27 and as early as January. Males usually begin
hibernation earlier in the fall and emerge earlier in
the spring than females. When they hibernate, their body
temperature is generally within o C of the ambient air
temperature. When active, their body temperature can
vary 8 to 10o C, without ill effect.
Mating activity begins
within 2 weeks after the squirrels emerge from
hibernation. Both sexes are sexually active for about 2
weeks. After a gestation period of 28 days, 3 to 14
(average 10) blind, naked, and toothless young are born.
Only 1 litter is produced per year. Young ground
squirrels weigh about 1/10 ounce (3 to 4 g) at birth.
Their stripes begin to appear after about 12 days and
their eyes open 28 to 30 days after birth. Young
squirrels are weaned and on their own after 6 to 12
weeks. Thirteen-lined ground squirrels are sexually
mature at 9 or 10 months of age.
Damage and Damage Identification
The thirteen-lined ground
squirrel’s preference for insects and field mice may
provide some benefit to the agricultural community.
Large concentrations of these ground squirrels in
pastures, fields, and gardens can, however, cause loss
of forages and crops. They dig up newly planted seeds,
clip emerging plant shoots, and pull overripening wheat,
barley and oats to eat the grain. They will readily feed
on commonly grown home or truck garden vegetables, often
damaging much more than they consume.
squirrels will invade golf courses, parks, lawns,
athletic fields, cemeteries, and similar wide open
grassy sites. Their burrowing and feeding activity can
cause major economic and aesthetic damage in such
squirrels are not protected by federal law. They are
protected by some state and provincial regulations
Damage Prevention and Control
Exclusion is expensive and
generally practical only in situations where cost is not
a primary concern. Thirteen-lined ground squirrels are
very good at digging and climbing. They can be kept out
of electrical substations or similar installations with
hardware cloth topped with sheet metal. Most electrical
substations or other secured installations are enclosed
by a chain link fence that can be made ground
squirrel-proof. Dig a trench 18 inches (45 cm) wide and
18 inches (45 cm) deep around the installation next to
the outside of the existing fence. Install galvanized
0.5-inch (1.3-cm) or smaller mesh hardware cloth (6 foot
[2 m] wide) across the bottom and up the side of the
trench nearest the existing fence, continuing 3 feet (1
m) up the fence. Backfill the trench. Securely attach
the hardware cloth to the chain-link fence. Attach a
piece of sheet metal, 2 to 3 feet (61 to 90 cm) wide, to
and above the hardware cloth. Adjust all gates to fit
within 0.5 inches (1.27 cm) of the support post and the
ground. It may be necessary to install a cement
threshold to keep squirrels from digging under the gate.
Activity in fields and
gardens can be discouraged by deep soil cultivation,
which destroys burrows and changes the habitat. Allow
grassy areas to grow as tall and as dense as possible,
consistent with local land use practices. Such
vegetation discourages ground squirrels but may
encourage population of other small mammals, such as
voles (Microtus spp.). Plant crops as early as possible,
before the squirrels emerge from hibernation, to reduce
losses to seeds and seedlings.
Deter ground squirrels and
other small mammals from feeding on crop seeds and
seedlings by providing them with an alternative food
source. At planting, broadcast 4 bushels of cracked corn
per acre (0.35m/ha) over the outside four to eight rows
adjacent to ground squirrel habitat. It also may be
necessary to spot treat fields in areas where damage is
expected or observed, especially if conservation tillage
Before using any
pesticide, read and follow all label directions. Many of
the pesticides used to control thirteen-lined ground
squirrels are Restricted Use Pesticides that may only be
sold to and used by certified pesticide applicators or
persons working under their direct supervision, and only
for those uses covered by the licensed applica-tor’s
certification. Some of the pesticides mentioned may not
be registered for every use in all states or provinces.
Contact your local cooperative extension agent,
USDA-APHIS-ADC, state or provincial pesticide regulatory
agency, or state or provincial fish and wildlife
department for information regarding special permit
requirements or endangered species restrictions.
Specific use instructions can be found on the individual
product labels. Only general use comments will be
presented here. Check the Pesticides section in this
handbook for sample labels.
None are registered.
baits can be applied by hand in, or broadcast on noncrop
areas such as rights-of-way, golf courses, ornamental
plantings, nurseries, parks, lawns, field borders, and
ditch banks. Apply 1 teaspoon (4 g) of untreated bait
(clean oats or other grains similar to the bait) around
each active burrow 2 to 3 days before applying treated
bait to ensure good acceptance of toxicants. Apply
prebait on a bright, warm, sunny day when the ground
squirrels are most active. Allow material to fall
through the grass to the ground. Do not apply to bare
ground and do not apply in piles. Two to 4 days later,
after the prebait has been eaten, place 1 teaspoon (4 g)
of treated bait in the same locations. Do not apply
prebait or bait near homes, where food or feed is grown,
over water, on roads, or other bare ground. Bury all
carcasses found and any uneaten bait at the end of the
applications, apply 4 to 6 pounds of prebait per acre
(4.5 to 6.7 kg/ha) in 20-foot (6.1-m) swaths using hand-
or ground-driven equipment. Two to 4 days later, apply
an equal amount of treated bait in the same location.
Special care must be taken to prevent application of
treated bait over bare ground or in areas of scant
vegetation, where it can pose a direct threat to
Fumigants should never be
used in or around buildings, or where there is any
danger that people, livestock, or other nontarget
animals will come into contact with the gases. Treat and
plug all burrows, wait 24 to 48 hours, and retreat any
burrows that have been reopened. Repeat this process
until all burrows stay closed. Most burrow fumigants
work best when the soil moisture is high and the air
temperature is above 50°F (10°C)
Aluminum phosphide tablets
and pellets can be used to treat thirteen-lined ground
squirrel burrows in agricultural and noncropland areas.
Label recommendations are to place 1 to 4 tablets or 5
to 20 pellets as far down into the burrow as possible.
The lower rates are recommended for smaller burrow
systems under high moisture conditions, and the higher
rates are recommended for larger burrow systems when
soil moisture is low. Seal the burrow entrance by
packing the opening with crumpled newspaper and then
shoveling soil over the entrance. Be careful not to
cover the tablets or pellets with soil when sealing the
burrow. Several states have placed additional
restrictions on the use of this material.
Gas cartridges that
contain potassium nitrate or sodium nitrate work
similarly and therefore will be described together. In
the closed burrow system, a burning cartridge produces
carbon monoxide (CO), carbon dioxide (CO< 2 ), and
consumes oxygen. To use a gas cartridge, prepare it
according to label instructions. Cut a clump of sod
slightly larger than the burrow opening with a spade or
other suitable tool. Kneel at the burrow opening, light
the fuse, and immediately place the cartridge, fuse end
first, as far down the burrow as possible. Place the
cartridge, do not throw it. Immediately place the sod,
grass side down, over the opening and cover with soil to
make a tight seal. Close any other openings from which
Gas cartridges come in
different sizes. Therefore, make sure the cartridge will
fit into the burrow before lighting the fuse. Some
cartridges come with built-in fuses; others must have
the fuse inserted by the operator. Check the specific
product label for instructions and prepare the cartridge
accordingly. Avoid prolonged breathing of the smoke when
using gas cartridges, and do not use them near buildings
or other combustible material because of the fire
A few ground squirrels
around a home garden or small row crop operation can be
removed easily using wooden-base rat-sized snap traps,
glue boards, or live traps. Snap traps and glue boards
can kill animals caught in them. If it is necessary to
restrict access to traps and glue boards by nontarget
animals, place the traps under inverted wooden boxes
with a 2-inch (5-cm) hole cut in each end. This will,
however, reduce trapping success.
Wooden-base rat-sized snap
traps are readily available and the easiest to use for
most home gardeners. The biggest mistake most people
make when trying to trap nuisance animals is not using
enough traps. Set traps in the areas where damage is
occurring, next to active burrows, or on active runways.
Peanut butter is one of
the most effective baits and is difficult for the ground
squirrel to remove without springing the trap. Pieces of
apple or other fruit, vegetable, or nut meat, can also
be used as bait. Securely attach these baits to the trap
trigger. You can increase the attractiveness of most
baits by scattering about 1/2 teaspoon of rolled oats on
and around the trap. Cover the set, leaving enough room
for proper operation of the trap. Check the traps every
24 hours and apply fresh bait. If more than 2 or 3 days
go by without the trap being sprung, move the trap to a
new location. If the bait is taken without the trap
being sprung, try using mouse-sized snap traps. Young
ground squirrels may not be big enough to spring the
Glue boards, either
commercial or homemade, can be used to capture nuisance
ground squirrels in residential areas. Place glue boards
in areas where activity or damage is occurring. Bait
them with the same type of material used to bait snap
traps. Place bait in the center of the board. Once the
animal becomes trapped, it can be killed and disposed
of. Glue boards do not work well in dusty, dirty
environments. Care should be taken when using glue
boards outside because they can be attractive to
children, pets, and nontarget wildlife.
Live traps are
commercially available from a variety of manufacturers
(see Supplies and Materials at the end of this manual),
or they can be homemade. Use live traps that are 3 to 5
inches square and 18 to 20 inches long (8 to 13 cm
square and 46 to 51 cm long). The 5 x 5 x 18-inch (13 x
13 x 46cm) chipmunk-sized trap works well.
Burrow-entrance live traps
can be constructed using 0.5-inch (1.3-cm) hardware
cloth (Fig. 3). The main body of the trap is formed from
a 12 x 20-inch (30 x 50-cm) piece bent to form a
rectangular box 3 x 3 x 20 inches (8 x 8 x 51 cm). The
joining edges can be secured with hog rings. Use hog
rings to secure a 3-inch (8-cm) square piece of hardware
cloth to one end of the trap. The trap door is made from
a piece of hardware cloth 2 3/4 x 8 inches (7 x 20 cm).
Attach one end of the door to the top of the trap with
hog rings. Recess the point of attachment about 1 inch
\(2.5 cm) to permit free movement of the door when the
trap is placed in the burrow entrance. Bend the opposite
end of the door so at least 2 inches (5 cm) of the door
are in contact with the trap floor when the door is
closed. A wire handle should be attached to the top of
the trap (Fig. 3).
Fig. 3. Ground squirrels
can be readily captured in this homemade live trap
(Adapted from Wobeser and Leighton 1979).
Before setting the trap,
spend some time observing the squirrels to determine
which burrows are active. Set the trap by wedging the
door end firmly into the entrance of an active burrow.
The closed end should be pointing into the air. Prop the
trap in position with a block of wood or other suitable
object. Gravity will hold the door closed until the
squirrel pushes past it to leave its burrow and enters
the trap. Dispose of trapped animals in accordance with
Snares made of 8 pound
(3.6 kg) test monofilament or wire fishing leader are
simple and effective. Leghold traps (No. 0 longspring or
coil-spring), and Conibear® traps (No. 110) can also be
used. However, the effort required to set them, compared
to snap traps, glue boards, and burrow-entrance live
traps, makes their use questionable.
Shooting can provide
control if the landowner is willing to put in the
necessary time and effort. All shooting should be
carried out in a safe manner and in strict accordance
with local regulations.
Ground squirrels were
often captured by the Native Americans that lived on the
central plains and the west coast by pouring water down
the animal’s burrow, thereby forcing the squirrel to the
surface. Similar methods of removing ground squirrels
still work. Flooding can enhance the effectiveness of
trapping and snaring. Avoid flooding burrows that are
adjacent to building foundations or other underground
structures that may be damaged by water.
Economics of Damage and
Control The exact cost of damage caused by the
thirteen-lined ground squirrel is difficult to quantify
because much of it probably goes unreported. For the
homeowner with one or two ground squirrels in the garden
or a farmer with a few ground squirrels in the field,
the animals may be more of a nuisance than a serious
pest. However, when large numbers are present, they can
cause serious losses. Thirteen-lined ground squirrels
have established colonies in and around borders of
minimum tillage corn fields in Nebraska. Extension
agents and farmers there have reported losses of 20 to
80 acres (8 to 32 ha) annually in fields during 1989 to
Results of a survey of
USDA-APHIS-ADC state offices, and of the Alberta,
Manitoba, and Saskatchewan Provincial Wildlife Services,
indicate that the thirteen-lined ground squirrel is only
a minor pest in most suburban areas, and a minor to
moderate pest in most agricultural situations. Indiana
ADC considers them a major agricultural pest in no-till
corn. As minimum tillage farming increases, the
potential for increased agricultural damage from
thirteen-lined ground squirrels may increase.
The most effective method
of controlling thirteen-lined ground squirrel damage
will depend on the situation and on the temperament of
the people involved. Wooden-base rat-sized snap traps,
live traps, or gas cartridges may be the best methods
for eliminating one or two animals from a garden. Burrow
fumigation may be the best method in truck gardens, or
in and around parks, athletic fields, and cemeteries
where the use of traps or poison could pose a hazard to
people, pets, and nontarget wildlife. In orchards,
vineyards and noncrop areas zinc phosphide treated baits
may be most economical.
We thank Richard Dolbeer
and Tom Seamans, USDA-APHIS-Denver Wildlife Research
Center; Douglas Andrews, USDA-APHIS-ADC; and David
Wolfert, USFWS for their editorial assistance in the
preparation of this manuscript.
For Additional Information
Burt, W. H., and R. P. Grossenheider. 1976. A field
guide to the mammals, 3d ed. Houghton Mifflin Co.
Boston. 289 pp.
Davis, W. B. 1966. The
mammals of Texas. Texas Parks Wildl. Dep. Bull. No. 41,
Austin. 267 pp.
Doutt, J. K. 1967. The
mammals of Pennsylvania. The Pennsylvania State Game
Comm., Harrisburg. 281 pp.
Gottschang, J. L. 1981. A
guide to the mammals of Ohio. The Ohio State Univ.
Press, Columbus. 176 pp.
Hamilton, W. J. 1963. The
mammals of eastern United States. Hafner Publ. Co., New
York. 432 pp.
Wobeser, G. A., and F. A.
Leighton, 1979. A simple burrow entrance live trap for
ground squirrels. J. Wildl. Manage. 43:571-572.
Scott E. Hygnstrom, Robert
M. Timm, Gary E. Larson
PREVENTION AND CONTROL OF
WILDLIFE DAMAGE — 1994
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 B-165
Great Plains Agricultural
Council Wildlife Committee