Farmers
are reporting crop damage from voles (field mice). Oval bare patches
and burrows in soybeans or wheat fields indicate voles are present. Vole
populations peak every 2-5 years. Cold harsh winters (2018, 2019) were
the vole bottom and populations rebounded due to a mild 2020 winter.
Snow and crop residue insulate voles against the cold. Voles do not
hibernate but they need 40 percent more energy to survive cold winters.
It is now time to view crop damage and to devise a plan to reduce vole
damage next spring.
Voles are 3-7 inches long, with short ears,
small eyes, short tails, and brownish gray fur. There are two types of
voles (meadow vole, prairie vole) that cause crop damage. Meadow and
prairie voles are similar in appearance except prairie voles may have a
yellow belly. Prairie voles’ mate for life and are normally seen in
pairs, while meadow voles are usually alone. Highly prolific, meadow
voles have 4-8+ litters per year, up to 11 young per litter under
optimal conditions of food and shelter, and average 40-50 young per
year. They wean their young in 12-14 days and their offspring may
reproduce in 21 days. Prairie voles have 2-4 litters per year with 20-30
offspring and their young reproduce in 35-40 days. Prairie voles have
higher survivability while meadow voles have greater than 80 percent
mortality. Most voles live only 6-18 months, reproducing quickly when
food and shelter are abundant.
Voles generally live in .25 to 1.5-
acre areas. They eat seeds and vegetation that have a high protein
(nitrogen) content or low carbon: nitrogen ratio like soybeans. In early
spring, voles eat newly emerging seedings or dig up the seed. They
graze soybean stems 6-10 inches up the stem. They feed every 2-3 hours,
staying close to their nest or burrow. In mid- summer, when the
vegetation grows high and food becomes scarce, voles migrate out, up to 2
miles away. They may return in late summer early fall, when crops are
harvested.
Voles are considered a keystone mammal because they are
a food source for many predators: hawks, owls, falcons, fox, coyotes,
etc. To combat voles naturally, place 10-foot high iron fence posts with
a bar as a perch around clusters of vole activity. Owls, hawks, eagles,
falcons and many birds of prey use perches as an efficient way to scout
and gather food. The American falcon or kestrels are great vole
predators. Perches can be installed after harvest, but keep a map of
where they are posted and paint the perches a bright color. Deer like to
rub against the posts and knock them over and no one wants to run a
steel post through their equipment. Coyotes eat more voles but have a
large 20 to 30-mile scavenging range while foxes stay in a much smaller
area. Avoid over hunting if vole populations are high.
In these
COVID 19 times, some farmers have invented a new sport. Rat terrors and
about 10 dog species are great “terrors of rats and mice.” A Michigan
farmer with 3 rat terrors reported killing 250 voles in two hours. He
helps the dogs by taking a shovel and disturbing active burrows so the
voles flee, increasing his vole termination rate. In summer, voles are
most active at night, right before sunset, or as the sun comes up. In
the winter, they feed during the day, often under the snow. A word of
caution, small dogs make great pets and hunters but do not allow them to
lick your wife or kids after a vole hunt! Voles carry many diseases
harmful to humans.
Modifying food and shelter are key strategies
to reducing vole populations. Fall mowing of ditches, waterways, cover
crops, and other tall vegetation down to 8-12 inches increases predation
by birds and mammals. Rotary hoeing in the fall or early spring
(especially early morning or before sunset) disrupts nests and
terminates many voles. At harvest, use chaff choppers to spread crop
residue evenly over the whole field. Cover crops should be a 50 percent
live-50 percent winter killed mix and should be drilled, not broadcast.
Tillage and poisonous baits are only 50-60 percent effective, so good
vole control requires a combination of management practices. New Alert:
If vole populations are increasing, so are slugs because they like the
same habitat! For more information, see hoormansoilhealthservices.com
for factsheets and power points on vole and slug control.