AND SHORT-EARED OWL IN ESSEX,
179
shire, belonging to the Crown, were suddenly threatened by entire
destruction in 1813-4, through vast numbers of mice severing the
roots of and barking the young trees. By digging small pits, eighteen
to twenty inches deep, about twelve to the acre, and thus catching
more than two hundred thousand individuals, aided by numerous
predatory creatures, the plague was stayed. Of the 28,071 caught
from September to January in Dean Forest, 27,931 were Short-tailed
Field Voles—the remainder belonging to the long-tailed species (Mus
sylvaticus, L.). In the three hundred acres of Dean Forest, "not
more than four or five plants were found which were not injured, or
indeed destroyed, by the mice. Many of the plants bitten through
were as thick as a man's arm; and the roots were gnawed so close to
the stem that some of the young trees were seen either reclining on
one side, or level with the ground."
Sir Walter Elliot records3 how Upper Teviotdale, Dumfriesshire,
and other border localities were invaded by swarms of this field vole
in the autumn of 1875 and spring of 1876 : "They did great damage
to the sheep walks, actually in some places completely destroying the
early pastures of the sheep." The Isle of Ely was visited in 1816,
and many other instances of the great amount of mischief done to
woodlands, cultivated fields, both pasture and arable, and gardens
could be given. Our member, Dr. Henry Laver, has put on
record4 the following specific details: "Noticing the large amount
of food consumed by a Short-tailed Field Mouse (A. agrestis),
which I am keeping in a cage, I determined to weigh the quantity
supplied and eaten in twenty-four hours. Just now I am giving it
clover, and find six drachms (apothecaries' weight) to be barely
sufficient to last it twenty-four hours, and as the little creature does
not, I suppose, much exceed an ounce in weight, the consumption is
enormous....."
These instances will give an idea of the destruction caused by
this prolific little creature—often erroneously attributed to rabbit
depredations. But "wheresoever the carcase is, there will the eagles
be gathered together." It is the Short-eared Owl (Asio brachyotus,
Forster) that seems specially commissioned to maintain the balance
of Nature in these micey visitations. The vole is nocturnal in its
habits, and falls an easy prey to the owl from above and the weasel
from below. Jesse, in the instance already referred to, says : "None
3 "Field," xlix, p. 77 (January 20th, 1877).
4 "Zoologist," 3rd ser., v, p. 461 (November, 1881).