INFLUENCE OF ANIMAL LIFE ON VEGETATION. 85 
servative rather than pernicious. Few wild animals depend for 
their subsistence on vegetable products obtainable only by the 
destruction of the plant, and they seem to confine their con- 
sumption almost exclusively to the annual harvest of leaf or 
twig, or at least of parts of the vegetable easily reproduced. 
If there are exceptions to this rule, they are in cases where the 
numbers of the animal are so proportioned to the abundance of 
the vegetable that there is no danger of the extermination of 
the plant from the voracity of the quadruped, or of the extinc- 
tion of the quadruped from the scarcity of the plant.* In diet 
and natural wants the bison resembles the ox, the ibex and the 
chamois assimilate themselves to the goat and the sheep; but 
while the wild animal does not appear to be a destructive 
agency ia the garden of nature, his domestic congeners are 
* European foresters speak of the action of the squirrel as injurious to trees. 
Doubtless this is sometimes true in the case of artificial forests, but in woods 
of spontaneous growth, ordered and governed by nature, the squirrel does not 
attack trees, or at least the injury he may do is too trifling to be perceptible, 
but he is a formidable enemy to the plantation. ‘‘The squirrels bite the 
cones of the pine and consume the seed which might serve to restock the 
wood; they do still more mischief by gnawing off, near the leading shoot, a 
strip of bark, and thus often completely girdling the tree. Trees so injured 
must be felled, as they would never acquire a vigorous growth. The squirrel 
is especially destructive to the pine in Sologne, where he gnaws the bark of 
trees twenty or twenty-five years old.” But even here, nature sometimes 
provides a compensation, by making the appetite of this quadruped serve to 
prevent an excessive production of seed cones, which tends to obstruct the 
due growth of the leading shoot. ‘‘In some of the pimeries of Brittany 
which produce cones so abundantly as to strangle the development of the 
leading shoot of the maritime pine, it has been observed that the pines are 
most vigorous where the squirrels are most numerous, a result attributed to 
the repression of the cones by this rodent.”—Bo1rEeL, Mise en valeur des Terres 
pourres, p. 50. 
Very interesting observations, on the agency of the squirrel and other small 
animals in planting and in destroying nuts and other seeds of trees, may be 
found in a paper on the Succession of Forests in Thoreau’s Hzeursions, pp. 
135 et seqq. 
I once saw several quarts of beech-nuts taken from the winter quarters of a 
family of flying squirrels in a hollow tree. The kernels were neatly stripped 
of their shells and carefully stored in a dry cavity. 
