THE SMALL MAMMALS OF ESSEX 51
We have relatively few recent reports of this species but this
should not be taken to indicate that it is becoming rare. Indeed,
press reports indicate that the reverse is true in the older urban
areas, where control methods are less successful than previously
because of the spread of warfarin resistant strains. Most of the
trapping and bottle-hunting has been done in areas some dis-
tance from buildings and our records represent the small popula-
tion that lives in fields and hedgerows for part of the year. Few
people have bothered to send in casual House Mouse records and
so the map gives a quite erroneous impression of the distribution
of this species in Essex.
Bank Vole (Clethrionomys glareolus (Schreber)) Map 9
Laver: "This Vole is by no means common in Essex, accord-
ing to my experience, although the first specimen recorded as
British was described by Yarrell from an Essex example (1832).
Probably more might be found if observers were careful to
examine all the Voles they met with..... The habits of
Arvicola glareolus (i.e. C. glareolus) appear to be similar to those
of the last species (the Field Vole), but I think they are never
found in such damp situations as the Field Vole. The only dis-
tinguishing characters to be entirely depended upon are the
teeth. Colour, length of tail, and brush at the end of it, are
uncertain marks in such a variable family, and I advise no one
to trust any of these traits singly in the identification of speci-
mens."
In fact, as the map and Table 5 show, the Bank Vole is now
known to be a very common and widespread species. The bottle
results are especially good evidence because the remains have
been identified using the tooth characteristics as Laver recom-
mends.
It is now well known (see Southern 1964) that Bank and Field
Vole habitats do not overlap much. Bank Voles normally live in
hedgerow, scrub or woodland with some ground cover. Unlike
Field Voles, they make extensive underground burrows and feed
on seeds as well as leaves. The capture of large numbers of Bank
Voles in the Rumsey's Nursery survey (Table 1) was somewhat
surprising as the waste ground area was more typical of a Field
Vole habitat although very few of the latter species were caught.
Yet even here the two species remained separate, Microtus occur-
ring in areas of pure grass, and Clethrionomys only in areas of
tall herbs.
Laver was obviously very cautious about accepting Bank Vole
records and this probably led him to make false conclusions about
the rarity of this species. There has been little change in the
availability of Bank Vole habitats since the end of the last century
and there is no reason to suppose that a real change in abundance
has occurred. Barn Owls, which produce the most easily collect-
able pellets, do not capture Bank Voles very often and a survey