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The signs that birds are starting
to breed in the woods and hedgerows are there for
everyone to see. They literally make a song and dance
about it. Their mammalian counterparts reserved and
modest in their private lives. I can see that the pace
of life is hotting up for the rabbits that are
devastating my lawn, the squirrels tearing round the
trees and the hares in distant fields, but there is no
sign of the hordes of mice and voles that must be busy
under cover.
This thought occurred to me when
I lifted the cover on a bank vole. I have always made
a point of raising planks, logs and sheets of
corrugated iron to see what may be lurking underneath.
Sometimes it is just worms and woodlice but this time
there was a field vole in a nest of grass.
Like small birds, bank voles and
other rodents suffer a huge turnover in population.
Life for them is brutish, by strict definition, and
short. Voles breeding in spring are the survivors of a
heavy winter mortality and consist mostly of animals
that were born in the latter half of the previous
year. Few survive into their second spring. Many
perish in the winter, a high percentage being weeded
out by owls, foxes and weasels, but the most
significant causes of mortality are starvation and
cold. Nevertheless, the death rate will rise even
higher in summer when the growing population competes
for food.
This grim picture is offset by a
high birth rate. There are three or four babies in a
litter, maybe up to seven, and litters are produced
every three or four weeks until October or later.
These young bank voles must then find a good home
where they have shelter from the elements and
predators (though not always from prying naturalists),
and where they can find enough beechmast, hips or haws
to store as winter provisions.
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