32 THE ESSEX NATURALIST
The Small Mammals of Essex
By David Corke
Department of Biological Science, North-East London Polytechnic
Romford Road, E.15
AND
Stephen Harris
Department of Zoology, Royal Holloway College, Englefield
Green, Surrey
Introduction
The small mammals discussed in this paper are the non-
flying species whose average adult weight is 50 grams or less.
There are ten such species found in the geographic county of
Essex:—three shrews (Soricidae), four mice (Muridae), two voles
(Cricetidae) and one dormouse (Muscardinidae). Because of their
small size, and the fact that either they are nocturnal or restrict
their diurnal activities to the cover of dense vegetation, these
species are very difficult to study by direct observation. This
probably explains why so few records of small mammals were
published in the Essex Naturalist before the formation of the
Mammal Group of the Essex Field Club in 1959. In 1898 the
Essex Field Club published Laver's important Special Memoir
which gives an indication of the status and distribution of each
species. Although most of Laver's accounts are subjective im-
pressions, which may (as will be discussed below) have been
influenced by occasional identification errors, they provide the
only good source of records from the end of the last century.
The Mammal Group has been able to use several techniques
that were not available to Laver. This has enabled a more de-
tailed, but still incomplete, picture of the distribution and rela-
tive abundance of the ten species to be built up. Our aim in
this paper is to summarise the information collected between
1960 and early 1972 (some of which information has appeared
in the Mammal Reports mentioned in the reference list) and
compare the present day picture with that recorded by Laver
at the end of the last century.
Methods
The only methods of recording the presence of small mam-
mal species used by Laver were the casual recording of
specimens found dead, caught by cats or household mouse-traps,
seen alive in the wild or reported by countrymen and naturalists.
All these methods have contributed to the present survey, but the
vast majority of the records have resulted from the use of the