CONTROLLING POCKET GOPHERS
The
pocket gopher is a medium-sized burrowing animal. They cause
damage both by what they eat and by the above ground mounds created when
burrowing. They are one of the most harmful and annoying
rodents.
The pocket gopher's name comes from
its external fur lined cheek pouches, one on each side of their mouth.
These pockets (pouches) are for carrying food and bedding. Food
consists mainly of the underground parts of plants.
Pocket gophers lead almost completely
subterranean existence. Gophers are antisocial except during the
breeding season. The gopher viciously repels another gopher if it
tries to invade a runway. Each gopher establishes its own
territory, covering 200 square feet for a young gopher to 2,500 square
feet for an older established gopher. The burrowing system consists of
a main tunnel-two to two and a half inches in diameter. These main
tunnels run nearly parallel with the soil surface. Gophers push
accumulated dirt from their excavations out lateral exits, forming
characteristic crescent shaped mounds. When the gopher is done and
moves to a new area, it will plug both exits.
In areas not irrigated, there is a
limited breeding season, sometime after the rains begin, when green forage
becomes plentiful. In such places there is usually only one litter
of young a year. In an area where food is plentiful, gophers will
breed throughout the year and a female may bear three litters.
Litters average five to six babies, but they can vary from one to
thirteen per litter. Gophers are polygamous.
EFFECTIVE CONTROL
Underground solitude, a characteristic
of the gopher makes control methods difficult and expensive.
However, persistent effort will reduce and eventually eliminate gophers
over a considerable area. Prompt attention to the first evidence
(such as fresh mounds) will often save valuable plants and prevent other
damage.
Control is most effective when green
surface vegetation starts to grow. Gophers are most active when
the ground is soft and before young are born.
METHODS OF CONTROL: Trapping,
flooding, exclusion, gassing, encouraging natural enemies, and poisoning
-- Control of pocket gophers is best accomplished by trapping and
poisoning. Bait or traps cannot be placed on top of the ground
near a gopher mound, but must be placed carefully in the underground
burrow.
TRAPPING: Because pocket
gophers live in small underground burrows special types of traps must be
used, an ordinary mouse or rat trap is useless. The most popular
trap is the Macabee®. It is approximately five and a half inches
in length and made of wire except the trigger. The next most
popular trap is a box trap with a choker loop. Traps are quick and
positive when properly set. After you have set the traps, tramp
down or kick the tops off all mounds nearby. The next visit will
show any new mounds where gophers remain and showing further effort is
necessary.
FLOODING: Individual gophers in
lawns and gardens can be forced out by sticking a garden hose down their
burrows. After turning the water on and waiting until the gopher
emerges you can club the gopher.
EXCLUSION: Where small gardens
or ornamental planting need protection you can use fencing. The
fencing made of sheet metal, concrete, or small mesh wire is acceptable
to use. The fence should extend down below the ground on all sides
at least two feet. On young individual trees or plants a wire-mesh
basket or cylinder can be used. It should also extend to a
depth of two feet below ground.
GASSING: When using gopher
bombs, you will have limited success because of the following factors:
the length of the burrow systems, the chance of leakage through the
sandy soil, and the fact that the gopher may quickly plug off his burrow
when a foreign substance is detected in the runway.
NATURAL ENEMIES: Birds of prey,
snakes, coyotes, badgers, foxes, etc. These are usually found in an
agriculture setting, not in a backyard or garden.
POISONING: The easiest and
least time-consuming method of pocket gopher control is by poisoning.
Using bait relished by gophers by placing it in the main burrows, with
as little disturbance as possible will give the best results.
To decide on a bait that gophers relish,
a laboratory ran tests on six different grains. The six grains
tested were barley, beans, cracked corn, milo, oats, and wheat.
It was found that given a choice of grain, gophers preferred milo and
barley over the others.
The poison presently recommended for
use is strychnine alkaloid. Grain can be coated with the
strychnine alkaloid without effecting the seed's germination properties.
Strychnine alkaloid is a relatively safe poison because (1) it is
extremely distasteful to humans, (2) an animal eating only the flesh of
a poisoned gopher will have no ill effects from the poison.
However, it is possible for an animal to obtain a lethal dose of
strychnine by eating a poisoned gopher that may have some bait in its
cheek pouches or undigested bait in its stomach. This type of
poisoning is unlikely, but it remains a possibility.
APPLICATORS
AND METHODS OF APPLYING BAIT
First you must know how to
locate the gopher's natural runway. Locate the gopher's natural
runway by using an iron bar, a strong stick, or other suitable tool.
Probe six to fifteen inches from the mound, on the side of the
horseshoe-shaped depression and probe eight to ten inches below the soil
surface. Once you have found the runway, the resistance on the
probe will decrease.
To apply bait with a
Gopher Bait
Applicator: Using the probe's end, probe around mounds to locate
runways (see above paragraph). Once the runway is found, lift the
handle to deposit bait in each active runway. Cover the probe hole
with sod or dirt carefully. Do not allow dirt to cover the bait.
Gopher Getter Midget
and Probe 'N Funnel
are other applicators that can be purchased for the ease of applying
the gopher bait into the runway.
Another way of applying the bait is
with a long-handled spoon. After finding the runway (discussed
previously), remove the mound's plug from the flat side of the
horseshoe-shaped mound using a shovel. Using a long-handled spoon,
insert one tablespoon of bait into each active runway. Close the
tunnel with soil carefully so the soil will not cover the bait.
This is a general overview of
gophers, their living habits and the control of them. I hope this
bit of information will help you control your gopher problem, whatever
method you choose. Good luck!
~ Brent Hazen
CONTROLLING
THE CALIFORNIA GROUND SQUIRREL
(Spermophilus Beecheyi)
The California Ground Squirrel is a medium-sized, burrowing rodent.
They are brownish in color with buff flecking; whitish wash on sides of
neck across shoulders to haunches enclosing a dark brown or black V
pattern on top of back shoulders, with V pointing forward. They
have a rather
bushy tail that is brownish-gray above and below, edged in white. Adults
range from 14 to 20 inches long and weigh 1 to 2 1/2 pounds.
BREEDING: They mate in early
spring, 1 litter of 5-8 young. Young first begin to burrow at
about 8 weeks of age.
SIGNS: They have burrows with the
entrance mound and radiating pathways.
HABITAT: Open areas, including
rocky outcrops, fields, pastures, sparsely wooded hillsides.
RANGE: Southern central
Washington, western Oregon, most of California, west central Nevada.
GENERAL INFORMATION: Active from dawn
to dusk, California Ground Squirrels form loose colonies, but
individuals tend to be antisocial. Several animals may occupy one
burrow, 3-6" wide, 5-200' long, but each uses its own entrance.
This hole, rather than the nearest, is the one the animal usually races
for when alarmed. Burrows are usually under a log, tree, or rock
when available, otherwise they're in the open, with a mound at the main
entrance. Some are used for many years by successive occupants.
While this ground squirrel may climb into brush or a tree to bask in
early morning sunlight, it otherwise remains on the ground. It
feeds primarily on plant material, including leaves, stems, flowers,
bulbs, roots, seeds, fruits, and berries, but sometimes also on insects
and small vertebrates. It often damages grain, fruit, and nut
crops, and its fleas often carry Bubonic Plague.
DAMAGE AND DAMAGE IDENTIFICATION:
High populations of ground squirrels may pose a serious pest problem.
The squirrels compete with livestock for forage, destroy food crops, and
serve as a potential disease reservoir. The mounds of dirt
excavated from their burrows in hay fields damage mowers and other
haying machinery. Ground squirrels feed on both immature and
mature grain crops. Burrow mounds cover vegetation and interfere
with harvesting.
DAMAGE PREVENTION AND CONTROL
METHODS:
Exclusion: Exclusion is
impractical in most cases because ground squirrels are able to dig under
or climb over most simple fences. Structures truly able to exclude
them would be prohibitively expensive for most situations. Sheet
metal collars are sometimes used around tree trunks to prevent damage to
fruit or nut crops.
Cultural Methods: Flood
irrigation of hay and pasture lands and frequent tillage of other crops
discourage ground squirrels somewhat. However, squirrels usually
adapt by living at the margins of fields, or in high areas in the
fields.
Poison Grain Bait:
Currently, direct population reduction with poison grain bait it is the
most practical method of ground squirrel control for most situations.
Since pesticide registrations vary from state to state, persons planning
control operations should check with their local Extension of Service
office for information on baits legal for their area. Once the
bait has been chosen, the following steps will optimize your chances of
success in control operations. Poor results are almost always the
result of not following these rules:
-
Be sure that the entire ground
squirrel populations is active. If a portion of the
population is in hibernation, it does little good to apply bait.
Baiting should never be done at the first sign of activity in the
spring or when the squirrels start to disappear into their burrows
late in the summer. A third period when baiting should be
curtailed is late in the gestation period and shortly after the young
are born. Females are relatively inactive above ground at that
time. This period varies locally, but it generally begins four
to eight weeks after emergence from hibernation.
-
Be sure that the ground
squirrels are readily accepting grain. Ground Squirrel
feeding habits vary with the time of the year. It is important
to test the acceptance of clean (untreated) grain, generally oats, by
each of several active burrows. If the grain in not eaten,
poison grain would not be eaten at that time either. The
question of when to bait ground squirrels is very complex, and there
are no hard and fast answers. Each person must determine the
correct timing for his own area by observation of ground squirrel
activity and testing for bait acceptance by the methods described
above.
-
Use fresh bait. Bait
that is more than a few months old should not be used. The
potency of most baits does not diminish significantly, but their
palatability to ground squirrels does. This leads to poor bait
acceptance.
-
Place bait properly. Proper
placement of bait is critical to successful control. Bait should
be set adjacent to each active burrow in the amount and manner
specified on the label. It should not be placed in the burrow
because squirrels are highly suspicious of food there. They are
more accustomed to foraging above ground for food. All active
burrows must be baited. Incomplete coverage of a squirrel colony
will result in poor control success.
Trapping: Traps are best
suited for removal of small populations of ground squirrels where other
control methods are unsatisfactory or undesirable. Jaw traps
should be placed where squirrels will travel over them entering and
leaving the burrow.
Conceal the trap by placing it in a
shallow excavation and covering it with 1/8 to 1/4 inches of soil.
Be certain that there is no soil or small pebbles beneath the trap pan
to impede its action. No bait is necessary.
Box traps may be set in any area
frequented by ground squirrels. Place them solidly on the ground
so that they will not tip or rock when the squirrel enters. Cover
the floor of the trap with dirt and bait it with fresh fruit,
vegetables, greens, peanut butter or grain. Experiment to find the
best bait or combination of baits for your area and time of year.
Wiring the door of the trap open for several days while replenishing the
bait daily helps overcome the squirrel's trap shyness and increase
trapping success.
Shooting: Shooting may
provide relief from ground squirrel depredation in situations where very
small squirrel colonies are under constant shooting pressure. It
is, however, an expensive and time consuming practice.
Fumigants: Because of
the comparatively great amount of labor required, poison gases are best
suited to small acreages of light squirrel infestations.
Ground squirrel burrow systems are often quite complex with several
openings and numerous interconnecting tunnels. This sometimes
makes gassing difficult.
Fumigants registered for ground
squirrel control include: aluminum phosphide (Phostoxin, Rotoz, Fumitoxin),
carbon disulfide, magnesium phosphide (Magtoxin), and gas cartridges.
If poison gases are used, be sure that all burrow entrances are sealed
tight with tamped earth. Gases work most effectively when soil
moisture is sufficiently high to prevent gas from seeping into the
earth.
This is a general overview of ground
squirrels, their habits, and control methods for them. I hope this
information will help you make an informed decision on the method of
control you decide to use.
