exposed the nuisance may be abated, but many of the damaged trees will have to
be cut off at the ground level in the hope that new shoots will spring from the
roots. During a long experience as a forester this is the first time that I have known
mice attack young trees during the summer months, and, in fact, only once before
in the winter.’
This mischief may have been caused by Bank Voles; it is a pity that
specimens were not sent for identification.
A very interesting and accurate article from the pen of Mr. J . Nisbet
appeared in the ‘ Field,’ and certain passages relating the different ways in
which various rodents injure trees are worth quoting:
‘ Of these the chief offenders are rabbits, squirrels, mice, and Voles. Sometimes
it is difficult to determine, on first inspection, to which class of rodents the
damage done may be due, unless the offenders have actually been seen at work.
The three main points for consideration in this respect are (i) the season of the
year, (2) the position of the injury, and (3) the appearance of the damage done.
‘ All of these three classes of rodents may do more or less damage to woodland
trees, young plantations, and nurseries during the winter months. But th e
injuries inflicted by squirrels at this season of the year are entirely different in
their specific character from those done during the summer months, when the sap
of the trees is in full flow, because in the former case they consist mainly in
biting off the topmost twigs in order to eat the buds, while in the latter they
take the form of peeling and ringing poles and trees for the sake of the sappy
cambium during hot, dry summers. I f large trees are barked near their base one
may be almost certain that it is the work of rabbits—or of hares if the latter be
at all plentiful, in which case the marks of the incisors are much larger than when
rabbits have been at work. But hares are not now so plentiful as they once
were, and they soon shun places where rabbits abound. Where, however, the damage
has been committed in young plantations up to about fifteen or twenty years of
age, in which the bark on the young trees is still fairly soft and tender, injuries
done at and near the base of the stems may be due either to rabbits or to mice
and Voles. • Here, again, as with hares and rabbits, the difference in the size of the
marks left by the incisors gives a fairly good clue as to whether the damage has
been done by rabbits or by mice or Voles. Apart from the difference in the actual
size of the marks, those made by the rabbits are not only fewer in number,
but are also more generally horizontal than the far closer and smaller marks
left by mice and Voles. But while the long-tailed field mouse {Mus sylvaticus)
gnaws only at the roots and within two or three inches above the ground, and while
the damage done by rabbits is confined to within the 12 in. or 15 in. they can reach
up to by standing on their hind legs, the Voles (the genus Microtus, characterised
by their short tail and legs, broad head, and small ears hidden in fur) gnaw both
near the ground and, except the water rat (M. amphibius), for a very considerable
way up the tree, owing to their being endowed with the power of climbing.1
‘ Of the three species of these climbing land Voles the true field mouse
{M. arvalis) is a poor climber, while the common Field Vole (M. agrestis)
climbs better, but the Bank Vole (M. glareolus) is by far the best climber of
the three. Hence, when the Voles swarm in woods during the winter, the two
first-named do more damage by devouring seed and mast, and by gnawing
the rind of saplings and poles near the ground, and taking the bark off the
foot of the young trees as far up the stem as 8 in. or 10 in., while the Bank
Vole oftens climbs to a considerable height in order to reach the soft bark.
Consequently, when injuries have been done to plantations at about n ft. to
12 ft. above the ground, they may have been caused either by Bank Voles or by
squirrels, the Voles climbing by means of the little branches. But the Voles
carry on their work of destruction during the winter, whereas the peeling and
ringing of trees by squirrels takes place in the summer season. Here again,
however, the incisor marks left by the squirrels (though often very indefinite
until the specimens have become old and dry) are much larger and wider
apart, and are more regularly perpendicular than those made by the Bank Vole.
And they generally extend from about 6 in. to 8 in. or 10 in. above some horizontal
branch, where the squirrel seats himself conveniently and proceeds to clean
away the soft bark and the cambium either nearly or else entirely around the
stem, in which latter case, of course-, the top of the tree dies off above the peeled
ring. . . .
‘ At Rannoch, in Perthshire, early in the winter of 1863-64 mice attacked
about 140 acres of mixed plantations of eight and fifteen years of age, consisting
of Scots pine and larch intermixed with oak, ash, sycamore, elm, beech, and
sweet chestnut; but on this occasion only the Scots pine suffered. Sir Robert
Menzies thus described the attacks and the means of suppressing them: ‘‘ Early
in the winter of 1863-64 the mice attacked the Scotch firs in both plantations
simultaneously, eating away the bark, and sometimes the wood all round, as high
as they could reach, which, assisted by the heather and long grass, was from
1 This, however, would only apply to the Bank Vole.