(^150) an environmenTal hisTory of Wildlife in england
was followed by further dispersal and by 1945 it was probably present in
every county except Norfolk, Suffolk, Cornwall and Cumberland.^62
The spread of the grey squirrel was bad news for the indigenous red
(Sciurus vulgaris). The grey was a larger and more aggressive animal, and
spent more time on the ground, where many of the principal foods consumed
by both species are most abundant.^63 It also lives longer and at higher
densities than the red and successfully steals its food.^64 The red only has the
advantage in pine forests. Here less food is available but, being a smaller
animal, it requires less, and is also better able to secure what there is, as it
can reach pine cones growing on fine branches. Increasingly out-competed
in deciduous woodland, it thus retreated to districts with extensive conifer
plantations. The grey may also have brought with it a virus, parapoxvirus
(with similar symptoms to myxomatosis found in rabbits), to which it was
more immune than the red. The advent of the grey may not, however, have
been the only factor in the decline of the native squirrel, the numbers of which
appear to have fluctuated significantly over the centuries, and which suffered
a dramatic collapse between 1900 and 1920, before the grey had made any
serious inroads. Habitat change – a decline in the density of hedgerow trees,
reducing the squirrel’s ability to spread through the countryside – and the
expansion of urban and suburban areas – grey squirrels are better suited
to life in gardens than reds – may also have contributed. But it is clear that
the arrival of the grey did have a direct negative effect. In 1945 a ‘survey
of the distribution of two species... showed that wherever grey squirrels
had been present for fifteen years or more, red squirrels had either vanished
completely or survived only in small scattered groups’.^65 Today, the red
has effectively retreated to the Isle of Wight, Cumbria, Northumberland
and North Yorkshire. Grey squirrels had, and have, other problematic
effects on the countryside, for they damage trees (especially sycamore and
beech) by removing the bark in order to reach the sweet, sap-filled Phloem
tissue beneath, sometime killing trees directly, more often weakening their
resistance to disease and fungal attack.
Other significant introductions of alien fauna were made in this period.
A number of new species of deer were released, partly out of interest, partly
for sport. Various kinds of Sika deer (Cervus nipon) – Manchurian, Chinese,
Formosan, and Japanese – were introduced at a number of places in the
late nineteenth and early twentieth centuries, of which the last managed to
establish itself in the wild and is now present in significant concentrations in
Kent, in Dorset and Hampshire, and on the Lancashire/Yorkshire border.^66
Chinese water deer (Hydropotes inermis) were likewise introduced into,
and escaped from, private parks, although here the main culprit may in
fact be Whipsnade Zoo in Bedfordshire, from where there were several
escapes in 1929. Preferring a habitat on the edge of water, water deer are
now established to a limited extent in the Fens and Broads of East Anglia,
and along the Suffolk coast.^67 Bizarrely, England now hosts a significant
proportion of the world population of the species, which in its homeland
elle
(Elle)
#1