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Pocket gophers are one of natures earth
movers. They are even better than
corporate engineers.
Hi I'm Leonard Askem, vertebrate pest
management specialist with Washington
State University.
During the next few minutes we're going
to see what gophers look like, where,
and how they live, and when they become
a problem how they can be effectively
controlled.
Pocket gophers are not always a problem
or do they become a pest. In natural
environments pocket gophers are useful
in reducing soil erosion and aerating
the soil to great depths.
The extensive burrow system allow water
to penetrate far below the soil surface.
The deeper soils are continuously mixed
and brought to the surface where they
are deposited as dark crescent shaped
or horse shoe shaped mounds.
Mounds along with dead plants are
indicators that pocket gophers are
active in a specific area.
All pocket gophers have stout bodies, are
short legged, have blunt heads, prominent
yellow incisor or front teeth, and large
deep fur lined cheek pouches on the
sides of their face in which they can
carry food.
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Gophers spend most of their time
beneath the soil surface and are
generally active all year.
They do on occasion forage above ground
particularly around the burrow opening,
where they can quickly escape if they
are threatened.
They may also migrate above ground in the
fall to new territories when their
current habitat has become too crowded,
or when food has becomes scarce.
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Pocket gophers also migrate and develop
new burrow systems because they are
solitary animal.
The only time that more than one animal is
found in one burrow system is during
breeding season. Generally once in the
northern United States and Canada, and
two or three times in the southern US and
Mexico, and when young are being raised
by the female.
Males are chased away by the females
soon after they breed.
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As I've indicated several species of
pocket gophers are widely distributed
throughout the United States.
In studies where the animals are watched
in glass chambers, gophers were able to
dig three feet of tunnels in loose soil in
about ten minutes.
In actual conditions these animals may dig
and occupy as much as 800 feet of tunnels
or burrows at one time.
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Most burrows are two to three inches in
diameter, parallel to the ground, and
depending on the type of soil, can be
found at different depths.
Shallow feeding burrows are sometimes
found 2-4 inches beneath the soil surface.
Nests and food caches are generally dug
6-8 inches beneath the soil surface.
In colder climates where the top
12-24 inches of soil might freeze, deep
winter nests and food caches will be built
24-30 inches below the surface.
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When gophers become a problem, or pest,
three types of control measures can
be used either biological, mechanical, or
chemical.
Biological control is a long term solution
that includes predator management and
habitat modification.
Natures own control agents, predators, can
be encouraged by changing some of the
habitat in the affected area.
Thickly grown fence rows and hedges can
be grown along the field borders to
encourage weasels, foxes, skunks, coyotes,
and many other four legged carnivores.
Trees in which birds of prey
such as hawks and owls,
can nest and roost can be planted
and preserved.
Where fence rows and trees can not be
quickly grown or where they might
interfere with the growing crop, perching
poles and nesting boxes can be erected
to help attract the birds to the site.
Another often overlooked control method
that uses a simple biological principal
is forage removal. The simple process
of eliminating the animals food source
with either a plow, herbicides, or crop
rotation. It is often enough to eliminate
a problem.
Gopher control however often requires
immediate attention, particularly where
high value crops or ornamentals are
involved.
When this is the case direct control
procedures become appropriate.
And effective if a few basic concepts are
followed.
Gopher control is most effective in the
fall, after the first heavy rain.
And when the gophers are most active.
Spring control can also be attempted,
if the population is small and there's a
slight chance of reinvasion.
Summer and winter control programs are
generally counter productive unless it's
in a mild climate.
So target areas should be small enough
so that the entire population can be
treated at one time and if necessary
retreated.
Third the appropriate technology should
be selected for the size and intensity of
the population.
Finding the gophers is easy, all you
have to do is find a fresh mound and
dig a hole at the open end of the horse
shoe.
Once the holes are opened a variety of
control methods can be used.
The first is fumigation.
Exhaust from diesel or leaded gasoline
engines can be used to fumigate a
burrow system. It is however time
consuming and may not kill many of
the animals if you have not closed up
all of the holes.
A less time consuming but expensive method
is to use gas cartridges like the
one here. Again, all of the exits must
be closed so that the gas doesn't escape.
Fumigants are only effective in tightly
compacted wet soils such as clay, or
clay lome where the gas can't escape from
the burrow system.
Gas tablets are slower acting, 2-6 tablets
are placed into each burrow covered with
water to activate them in dry soil.
Then sealed into the chamber with wadded
paper and dirt.
The wadded paper keeps the gopher from
pushing the tablet out of the burrow
when they find them.
None of the gasses are effective in loose
dry, sandy, or sandy lome soils.
Gas is used in these soils will rapidly
spread into the surrounding soil and not
throughout the tunnel system, where it is
the most effective.
A more effective control method,
particularly on small populations, are
traps. Traps can be used when we only have
a few animals to catch or are concerned
about other animals that might be
effected by the use of chemicals such
as the ones we just talked about.
The right trap, practice, and a little
patience however are required.
Traps used for rats, mice, and larger
mammals do not work with gophers.
The gopher must be caught in their burrows
where space is limited.
Two effective gopher traps are the box
and the Macabee.
Both of these traps should be placed
in the main burrow 6-8 inches below the
ground where the gopher is most active
each day.
Each trap should be placed well back
into the hole and then secured to a stake
with a wire or a chain, so that it cannot
be pulled into the burrow by a dying
animal or carried off by a scavenger.
Traps should be checked
and reset 2-3 times a day.
Until all of the animals have been
caught.
If you are not sure about your success,
leave the holes open for a day and then
recheck them. If the holes have been
closed the gopher is still alive, well,
and living off of your land.
When the population becomes quite large
trapping becomes very time consuming.
When this occurs remember the alternatives
are possible.
One of the most common and effective are
poison baits.
One type of baits are waxed grain bars
treated with anticoagulant chemicals,
that have been developed and tested at
two western universities.
Bait bars are a safe and easy to use
method, designed when there are too many
animals to trap and where acute or highly
toxic baits cannot or do not want to
be used.
After the bars have been placed into the
burrows and covered with soil, they become
a semi permanent bait station that will
last several months, or until the wax
that holds the block together sloughs
away and the bar dissolves.
Bait bars are consumed over a short period
of time, generally 7-10 days.
Bait bars like these carrots are moved to
the nest or food cache, by the gophers
where they become a short term reservoir
of poison bait for any animal that moves
into the burrow system after the current
resident has been killed.
Each treated area should be checked
every two weeks, and where activity
reoccurs new bait bars inserted into
the tunnels.
Another way for treating gophers is to use
poison bait inserted through a hole
with a machine.
Instead of digging a hole with a shovel,
a sharpened rod or prob can be inserted
at the open horseshoe end of the mound
until the runway is found.
Once the runway is found, the prob is
pulled out, turned over, reinserted, and
rotated slightly to enlarge the hole.
A teaspoon of bait is then dropped into
the burrow and the hole gently closed with
a clot of dirt or leaves.
If not properly closed the gopher,
attracted to the fresh air and sunlight,
will plug up the hole and in the process
cover the bait.
Another way to treat gophers is to use
a bait dispenser.
After the bait has been dropped into
the burrows, never stomp on the hole,
like I'm doing here, the loose soil from
the hole will cover the bait and the
gopher will not find them.
The most common gopher baits are a
strict nine treated; oats, barley, corn,
and milo.
Control can generally be accomplished
in 24-48 hours.
Anticoagulant treated grain and pelletized
baits are also available.
They are also very effective if used
properly, but take longer and sometimes
require multiple applications, before the
animals can be controlled.
As with all anticoagulant chemicals
registered for agricultural use, the
targeted species must feed on the treated
baits continuously for several days.
Often 5-7 or more before they die.
Burrow building machines are designed
to place lethal quantities of
1 1/2-2 pounds of rodenticide per acre
beneath the soil surface.
Artificial tunnels are generally placed
20-25 foot intervals to intersect active
burrow systems.
A coulter cuts through the sod and roots
in front of a plowshare and slotted
torpedo.
Two packer wheels compact the soil
behind the plowshare and over the torpedo,
while measuring treated grain through a
spring activated trap door.
Treated grains in the supply tank are
dropped into the hollow tube behind the
plowshare and into the slotted torpedo
where they are left for the gopher
to feed on.
Burrow builders can be effective for large
and extensive populations, if the
following steps are taken. First, check
the soil moisture. Conditions are just
right, when the soil holds together
without crumpling or dripping water.
Soils that are too dry or too wet, will
not build good artificial tunnels.
Second, find the average depth of the
natural burrows with either a prob
or shovel. Then set the depth of the
torpedo by adjusting the height of the
packer wheels, so that the artificial
tunnels will be at the same depth as the
burrows.
Next, set the coulter deeper than the
torpedo. If this isn't set properly, like
this machine, a large trench filled with
broken roots rather than a clean tunnel
will be plowed through the soil.
Finally, adjust the spring loaded metering
gate so that the right amount of bait
is applied with each revolution of the
packer wheel. Strict nine treated baits
generally work best, and anticoagulant
treated baits may also be effective.
Pelitized baits should be avoided.
This machine has had some very important
modifications made to it.
As we've seen on the earlier machines,
they had straight shanks which gave us
some problems.
This one has a shank that has been built
out and longer angle, the tube has been
extended, and also has a beak on the
bottom. The other important modification
is that it has two spring systems.
The first a spring loaded coulter, that
allows it to ride over rocks and large
roots without breaking.
The leading edge of the plowshare has also
been changed. This forces the uncut roots
up to the top so that they do not ball up
and destroy the artificial tunnel.
The third modification has been to replace
the sheer pin with a tractor clubus, that
unlocks when the torpedo hits a stationary
object.
All of these modifications have increased
the efficiency of the burrow builder,
particularly in rocky soils and forests.
Like any method the machine application
of rodenticides has it's advantages
and disadvantages. The major advantage
is that lethal amounts of rodenticides
can be efficiently placed at the proper
depth over a large area in a relatively
short period of time.
The major disadvantage is that these
machines may promote gopher investations
if they are not used properly.
In any control program, few population are
completely exterminated.
Most control programs are successful if
the number of animals are reduced by 85%
or more.
When burrow builders are used, like in
this orchard on the left, all of the
colonies are connected by the artificial
tunnels.
Animals that have not been killed during
the treatment can quickly invade the open
burrow systems through the artificial
tunnels.
Invading animals from untreated border
populations can also re infest the
treated field through the artificial
tunnels that can last as long as two
or three years.
Within a short period the entire site
can be completely reinfested and the
process repeated.
Two modifications can be used to keep this
from happening.
One, is to insert bait bars in the
artificial tunnels to kill any invading
animals.
Another, is to pull the burrow builder
out of the ground between invested areas
or in large infestation every 75-100 feet.
If done properly in moist soils, the
torpedo will slide out of the ground after
the packer wheels have stopped turning
so that no poison grains are exposed to
other animals.
This should not be done in dry soils
because the tunnels will collapse
or the torpedo will rip out the last few
feet and expose the bait.
Finally, after you think your work is done
check it out. Each area should be
monitored for survivors and immigrants.
Before walking away from a treated
mound kick it over. New mounds should
be treated as soon as they appear and not
left until next year, when the colony has
has a chance to grow.
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During the last few minutes, you've had
a chance to see what gophers look like,
where and how they live, and why it's
important as one of the worlds greatest
excavators.
You've also seen how biological approaches
such as habitat management can be used
to achieve long term results.
You've also been introduced to a variety
of direct management techniques.
These have been fumigants, using
carbon monoxide gas cartridges and
tablets.
Traps, bait stations, direct baiting with
probs and dispensers, and burrow building
machines.
All of these management practices and
techniques require patience and
perseverance. With time, however, they
will provide you will effective controls.
We hope that these hints have been helpful.
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