DTFLUENCE OF ANIMAL LIFE ON VEGETATION. 83: 



Influence of Animal Life on Yegetation. 



The influence of wild quadrupeds upon vegetable life has been 

 little studied, and not many facts bearing upon it have been record- 

 ed ; but so far as is known, it appears to be conservative 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 consumption almost ex- 

 clusively to the annual harvest of leaf or twig, or at least of pai-ts 

 of the vegetable easily reproduced. If there are exceptions to . 

 this rule, they are in cases where the numbers of the annual are 

 so proportioned to the abundance of the vegetable that there ia 

 no danger of the extermination of the plant from the voracity of 

 the quadruped, or of the extinction of the quadruped from the 

 scarcity of the plant.* In diet and natural wants the bison re- 

 animal, see L. H. Morgan's important monograph, The American Beaver and 

 his Works, Philadelphia, 1868. Among the many new facts observed by this 

 investigator, is the construction of canals by the beaver to float trunks and 

 branches of trees to his ponds. These canals are sometimes 600 or 700 feet 

 long, with a width of two or three feet and a depth of one to one and a half. 



* 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 espe- 

 cially 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 pineries 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." — Boitel, Mise en valeur des Terres pauvres, p. 50. Journal of For- 

 estry. No. 20, pp. 569-570, contains an article stating that squirrels are very 

 fond of sap, and a large English landholder informs me that these rodents de- 

 stroyed a great number of fine beeches in his woods by gnawing through tha 

 bark to reach the sap-vessels, thus completely girdling the trees. 



Very interesting observations, on the agency of the squirrel and other small 



