permaculture

[Lawrence London <lfljvenaura@gmail.com>]

Voles and Controlling Them
http://www.pitcherplant.com/diseas/voles.html

Voles
Tunneling Rodents that eat plants

[image: image of pine vole]
One of many Vole (Microtus) species, the Pine Vole is a bit smaller and has
a shorter tail than the Meadow Vole.

[image: close up of vole face]
Unlike moles, voles are mostly plant eaters. These images show the tiny
eyes, small, delicate feet and stubby tail which help identify voles. While
moles will make long, ridged tunnels visible from above ground, voles tend
to scratch out more invisible runways. Often, moles will serve as the
"highway crew" and make tunnels in search of grubs and worms. Voles will
often follow the mole tunnels and eat the plants which the moles ignore.
Entire apple orchards have been lost to vole damage and we have seen fairly
large chestnut trees killed by voles that ate their roots off. We have lost
thousands of plants and countless vegetables to the voracious voles. There
are very few plants that voles will not eat. They can have several litters
a year, with 1-11 young per litter. Yikes!

Most voles are in the genus Microtus. Despite being the most common mammal,
they are seldom seen because they are usually hidden beneath mulch, leaf
litter and earth. While many people believe cats can control voles, this is
almost never true, especially with vole species that travel deeper in the
earth. Natural predators include owls, foxes, wolves, weasels, shrews and
snakes. The Mole snake, or Mole King snake (Lampropeltis rhombomaculata) is
one of the few predators which can follow vole tunnels and so is one of the
better predators. Unfortunately, control by predators is rarely
satisfactory in a garden setting. While some poisons are listed for vole
control, these can be dangerous to other animals and must be used with
extreme care. We prefer to use several different kinds of mouse traps,
along with physical barriers that inhibit voles (or moles) from tunneling
into garden areas.

Using Barriers

In some gardens, especially vegetable gardens, it is possible to make a
trench around the garden, about a foot deep. This is more easily done right
after the garden is tilled. Most voles, tunneling right beneath the
surface, tend to turn back when they hit the trench and they are reluctant
to cross on top of the ground. It helps to make a trench down to harder
ground, if possible. Vigilance is necessary and gardeners should be on the
lookout for new holes on the garden side of the trench. Rob has grown
potatoes and parsnips in vole infested areas using this method. Mulch or
straw should be avoided in vole problem areas.

In some cases, such as a bog garden or flower bed, it may be more effective
to remove the soil and line the bog or bed with galvanized steel mesh
(hardware cloth), a layer of rock, or heavy-duty weed barrier. Any barrier
needs to be without underground openings and extend to the surface. (See
our Bog Making web page for more details.) While voles can chew through
weed cloth, they usually don't, especially if one patrols the perimeter and
collapses any approaching tunnels. We havebog gardens protected in this
fashion. Doubling or tripling a weed cloth layer helps. Again, avoid
mulches and look for new entry tunnels. Snow can be a problem, since voles
will travel quickly on top of the ground, under cover of snow.

Trapping Voles

Traps can be one of the better methods of vole control. Traps are best set
during the evening and are more effective if you can cover the traps with a
box, plastic pots, or anything to make the spot darker while still allowing
the traps room for motion. Here, the most successful bait has been Granny
Smith apple, cut into pea-sized pieces. Traps should be placed just outside
of tunnel entryways. A couple pieces of apple, dropped into the tunnel,
allows the aroma to draw in the rodents. Try to trap an area, not just a
single tunnel. Traps should be checked daily, especially live traps.

We've tried a couple designs in live traps, some of which can catch up to
fifteen mice or voles. So far, the best results have been with the type of
repeater trap that has a wind-up spring. A paddle wheel flips the rodents
into a metal chamber. It's important to put some apple inside the trap, in
the "holding" area, in the metal pathway and also where the rodents can't
get to the bait-inside the metal box on the trapping mechanism side of the
device. Usually, the top on these traps slides off. Be sure to check the
trap at least daily. The advantage of live traps is that you can release
other animals that might accidentally get caught. We have caught shrews,
lizards and even a flying squirrel in these traps. If you are not familiar
with small mammals, you might want to pick up a field guide to mammals.
Shrews, for example are good to release as they feed primarily on insects,
worms and rodent young. Shrews often live in the same area as voles. While
sharing the features of tiny eyes and small feet, shrews have pointy noses
and sharp teeth. Use caution releasing shrews, they are occasionally fierce
and confront much larger animals, even people! Most folks drown voles in a
five gallon bucket of water. If you want to release them far away, a meadow
is usually suitable; just don't release voles in cultivated/farmed areas.

Regular, snap type mouse traps can be very effective in killing voles. When
baiting this style of trap, try to cut pea-sized pieces of apple that
include some skin. If the skin is slid under the bait bar's hook or teeth,
it will be harder for a rodent to steal the bait. Again, drop a couple
pieces of apple inside tunnels. Voles often turn cannibalistic and a trap
with fragments of skin usually indicates additional voles.

There is another style of repeater mouse trap which does not have a paddle
wheel. This type has entry ramps that are spring loaded or counter
weighted. Rodents go in but can't get out. So far, we have had poor results
with this type of trap. Voles are bigger than common mice. For this reason,
the less expensive, plastic, live mouse traps may not work well or at all.

Whatever methods you use to control Voles, be vigilant and scout for
shallow tunnels or evidence of new infestations. Extending the control area
beyond the gardens you're protecting is a good idea. Ignoring Vole problems
can lead to disastrous overpopulation and the inability to grow most
plants.