182
THE ESSEX NATURALIST
Stortford, Quendon, and Mountessing. Colonies are known to
exist around Colchester and it has been seen at Witham and
Galleywood. Although usually the Yellow-necked Field Mouse
is said to be found in isolated colonies, the records from Margaret-
ting suggest that the area may be unusual in the size of the colony.
However, any concrete conclusions about the Margaretting colony
must await the results of further work. To date, 24 specimens
have been taken.
Harvest Mouse: Micromys minutus soricinus (Hermann).
Even in 1898 (Laver) the species was not thought to be com-
mon in Essex. Recent records of the Harvest Mouse are few, and
it certainly seems to be scarce in the county. It was recorded in
1958 from the region of the Stour. A few isolated records are from
Colchester (1958), Elsenham (1959), Mersea Island (1958), Foul-
ness Island (1961), and Romford Sewage Farm (1959). The only
records of moderate numbers of the animal are from West Berg-
holt corn ricks where 13 were taken in February, 1959, and also
18 from wheat ricks in December, 1958 (R. H. Davis and F. P.
Rowe in litt., 1963). None has been taken in Longworth traps
by members of the Essex Field Club.
House Mouse: Mus musculus domesticus Rutty.
This species is obviously known in the towns of Essex although
few records have come to hand. It is reported from Foulness
Island, Dawes Heath, Great Baddow, Woodford Green and gene-
rally in suburban Essex. It was taken in numbers during wheat
and barley threshing at West Bergholt (R. H. Davis, 1963). It is
common in the vicinity of houses and other buildings, in par-
ticular corn stores.
Black Rat: Rattus rattus (Linnaeus).
In 1858 the species was considered to be virtually extinct in
Essex, although there were a few records from East London. At
about this time, however, they were present in large numbers
at Great Yarmouth. During the war years there was a great in-
crease in the numbers of Black Rats in east London, and a few
records are still obtained from the Poplar and Silvertown areas
in the vicinity of warehouses. The Club's records are notably
deficient in references to the Black Rat, and it is hoped that more
information on this species will be forthcoming.
Brown Rat: Rattus norvegicus (Erxleben).
This is possibly our only truly ubiquitous Essex mammal,
for it is common in both hedgerow and town. The numbers of
Brown Rats have increased considerably in the Epping Forest
area in the past few years, especially in the region of ponds. The
apparent increase of the Brown Rat in aquatic habitats may be
due to the greater number of fishermen in recent years, many of
whom leave bread bait and discarded food lying by the waterside.