72
THE ESSEX NATURALIST
from the north-east side. Beven noted that the distribution of open spaces
allowed Grey Squirrels to penetrate nearer the centre of London from the
north and south than from the east and west.
In the 1959 Squirrel Survey Lloyd (1962) reported that the eastward
spread in Essex since 1955 had been much slower. In the south-east corner
of Essex very little advance had been made, although in north-east Essex
a more marked advance of up to ten miles occurred.
Several factors contributed to this reduced rate of advance. To the
extreme east and south-east of the county there are very few trees and the
habitat becomes comparatively less suitable, and as a result colonisation
has been slow. Also, during the 1950s there was a marked reduction in
Grey Squirrel numbers. Lloyd (1962) recorded a reduced tree-seed yield
in 1954, followed by a squirrel breeding failure in 1955. This was then
followed by a doubling of the squirrel bounty in 1955. It is doubtful
whether this last move had any major effect on the squirrel population,
although it might have slightly delayed the recovery of the already reduced
population. In Epping Forest, during the period 1950 to 1965, squirrel
shooting was systematically carried out by a party of Forest Keepers,
armed with squirrel poles, traversing the Forest two or three times a year
during the winter months. Since in this area the same effort was applied
each year the number of squirrels killed is indicative of population changes,
and this is shown in Figure 1; a similar decline and recovery of the squirrel
population was seen throughout Essex.
The reduced rate of spread of the Grey Squirrel in Essex during the
period 1955 to 1960 was probably due to a combination of the above
factors. Yet despite these adverse conditions, by 1960 most of Essex had
been colonised by Grey Squirrels, leaving only a strip along the east coast
and Thames Estuary uncolonised (Map 3).
1965
Figure 1. Numbers of Grey Squirrels killed each year in Epping Forest, from
1950 to 1965.