174 The Mammalia of Essex; a Contribution towards a
the great and easily distinguishing feature separating
Muridae and Arvicolidae. The Water Eat, for its size and
numbers, does less damage to man than any other member
of the family, its principal food being aquatic vegetables,
and it only takes what man can well spare. Occasionally,
when they are abundant and the weather is severe, they do
a little mischief to osier beds, but the injury they inflict
on the farmer is so small as not to be worth consideration.
The little animal is common in all parts of Essex, wherever
there are sluggish streams or stagnant water in sufficient
quantity to hide it. It will be well to bear in mind that it is
sometimes quite black in colour, and has been described (by
Macgillivray, 'Nat. Lib.' xvii. 257) under the name of
Arvicola ater, but this is merely a variety. This dark variety
has occasionally been mistaken for the old English Black Eat
(Mus rattus), and many of the supposed appearances of the
latter animal can thus be explained.
Arvicola agrestis. Common Field Vole.—Bell says that
A. agrestis may always be distinguished by the character of
its second upper molar, which has five cemental spaces,
whereas the same tooth in A. arvalis (which has not yet been
found in Britain), as in all the other European voles, presents
four spaces. This vole abounds sometimes to such an extent
as entirely to destroy the herbage, and from the quantity it
consumes (in confinement I have known one eat six drachms
of clover in twenty-four hours) one can quite understand
the devastation caused by it when existing in numbers. Not
only is herbage eaten, but, according to Bell, "many years
since the plantations of young oaks in New and Dean
Forests were destroyed." Its insatiable appetite compels it
to be abroad at all seasons of the year and all hours of the
day, but I have noticed those I have kept in confinement to
be more active towards and during the evening. I never
could make them very tame, and they appeared to me to be
rather stupid. The nest is usually placed amongst the roots
of the grass, sometimes under fallen timber. The young are
from four to six in number, and there are generally three or
four broods in a year. Weasels, owls, and kestrels are their