Westcountry Mole Control
The mole control specialists
The average Mole weighs in at approx. 4oz. and is about 6 inches long,
with dark grey hair, not black as is often supposed and is velvet-like
in texture. The Mole is not blind as is commonly thought - but its eyesight
is decidedly poor. This is only to be expected in a creature that spends
most of its life in subterranean darkness. Moles need to eat their own weight
daily, relying mostly on earthworms, but will also eat slugs, beetles,
spiders, centipedes, and leather-jackets. They will eat carrion, usually
a dead bird or mouse which it comes across on an expedition above ground,
but surprisingly, they will not eat vegetable matter.
Moles are pests which are very hard to get rid of. Small mounds of loose
earth (mole hills) appear when moles are active. Moles can bite through
surprisingly thick roots which interfere with their tunnels, but they do
not usually eat plants. The damage they cause is indirect; their activities
undermine plants allowing the roots to dry out. The shallow tunnels can also
disturb annual crops. Mole hills in a lawn can make mowing difficult and
spoil its appearance. There will be a system of permanent tunnels about
30-60cm below the surface which are unlikely to be detected from above.
It is the shallow, feeding runways which trouble gardeners.
Moles are highly territorial and generally live
alone in an extensive tunnel system covering an
area of 0.1 to 1.6 ha (¼-4 acres). Molehills are
created as the animals extend and repair their
tunnels, which act as traps to catch their main
prey, earthworms. One mole can produce a
considerable number of hills, particularly where
food is in short supply. Three or four young are born in the spring and
these disperse, generally over-ground, in midsummer
to try to establish their own territories.
Moles as an agricultural pest
Contamination of silage - Arguably, the most important single problem associated with moles is the pollution of
silage. In a 1970 survey conducted by the Pest Infestation Control Laboratory (MAFF), participating farmers listed the
deleterious effects of moles on silage as a major concern. The problem occurs when soil from molehills is collected with grass cut for
silage. Bacteria present in the soil, especially Clostridium spp., lead to the formation
of butyric acid, which can adversely effect the fermentation and preservation of silage. This in turn can
reduce the nutritional value of silage or, in some cases, render it unpalatable, thereby
affecting both milk and beef production. Another common problem occurs when Listeria monocytogenes in the soil contaminates
silage resulting in listeriosis in sheep and cattle. Up to 10% of animals in a flock/herd may be affected.
Covering of pasture - In a survey of Welsh farmers in the late 1970’s,
the reduction of grazing areas by molehills was regarded as the most serious and
widespread of all types of mole damage. In subsequent field trials, it was observed
that the loss of grazing area was up to 18%. It has been calculated that the amount
of soil deposited on a meadow by moles to be 32 tons/ha (dry weight) with a volume of
m3/ha, covering an area of almost 400 m2. Similarly, a study carried out in 1959 found
that in parts of Czechoslovakia 8-10% of permanent grass fields were taken up by molehills
each year, and that the loss in grass yield amounted to about 15% due to the effect of the
molehills on the grass cover. In one example, 1 ha of pasture was covered with 7,380
molehills weighing 64,500 kg with a volume of 40 m3. A study in Poland in 1976 recorded
21,063 molehills on 1 ha of pasture, 11.2% of which was consequently unavailable for
grazing. Clearly, this amount of surface soil will appreciably reduce the amount of feed
available to livestock and thus represents a considerable loss of milk and meat to the
farmer if no action is taken.
Damage to agricultural machinery - Molehills may interfere with harvesting
and cause considerable damage to farm machinery. The blunting of machine blades is
one of the main concerns of farmers when clover and grass are cut very close to the
ground to produce silage; similar damage has been noted when corn, peas and soya
beans have been harvested. The tendency for moles to bring stones to the surface
can lead to increased machine damage, as can the consolidation and enlargement of
molehills by invading ants.
Damage to young plants - On arable farms, the uprooting of seedlings
and young plants is considered one of the most serious types of damage attributed to moles.
The damage usually occurs as a result of moles raising the roofs of their tunnels, either
killing plants directly as they are pushed up onto the surface or by depriving their rooting
systems of soil and water which may also lead to the exposure of roots to frost. In Czechoslovakia,
a study reported up to 25% of young sugar beet plants being thrown up onto the surface at
one site. In Britain, root and ground fruit crops are susceptible to similar types of
damage.
Degeneration of pasture and weed invasion - The exposed soil of newly
formed molehills is often the first area of fields to be colonised, invariably by volunteer
weed species, which may further invade the pasture and dilute the sward. This has the effect
of steadily reducing pasture quality and consequently production. In a quantitative
study it was found that Agrostis spp. was the most frequent colonisers of molehills regardless
of sward use. Within two years, most molehills in the study were covered by almost pure stands
of Agrostis spp. at which point the vegetation appeared to stabilise. The study also noted an
association between the presence of molehills and the spread of thistles (Circium arvensie),
which, at one site, accounted for 8% of the ground cover. Another study discovered a similar
connection reporting that the number of thistles per square yard of mole infested ground was 6.9
compared with 0.7 in an adjoining mole-free area. In a later study, germinated seeds from molehills
were collected and it was found that only a very small proportion of the seedlings that emerged
were high-quality fodder grasses. Weed species contributed most to the emerging sward. Thus,
grass species are more likely to colonise a molehill by vegetative means, but they have to compete
with weed species better adapted to colonise bare soil.
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