26 AN ECONOMIC STUDY OF FIELD MICE. 
a small orchard of apple and pear trees near Washington, I). C, was 
under observation from October to April. Attacks by meadow mice 
began in the early fall, possibly in August. They were continued 
during every succeeding month, being greatest during two short 
period- of -now. Independent of snowfall, they were greatest in mild 
and least in cold weather. A few trees had no weeds or grass near 
the trunks, and these escaped injury. The neglected condition of 
this orchard appears from a photograph (PI. IV) taken January 24* 
190G. Adjoining the orchard was a tangled thicket on low. moist 
ground, in which meadow mice were abundant. 
On March 1G, 1906. I found that of 380 apple trees. 164, or over 43 
percent, were ruined, being completely girdled, some to a height of 
8 to' 10 inches above the ground. Thirty-six others, nearly 10 peri 
cent, were less badly injured, while 180. or 47 percent, apparently, 
were uninjured. 
Of 200 pear trees in the orchard 50 were more or less seriously 
damaged. The injury to these was inflicted early in the fall. 
The nature of the damage to individual trees in the orchard is 
well shown in Plate V. 
INJURY TO FOREST TREES. 
As an example of the danger from field mice to which planta- 
tions of forest trees are exposed, the following is cited: In L813 
and 1814 young plantations of trees in Dean and Xew fore>t^. Eng- 
land, were greatly damaged by mice, probably M. agrestis. The 
damage was to planted acorns, two-thirds of which were destroyed, 
and to holly, oak. and chestnut trees, some of which were .*> years 
old. Xot only were the trees girdled above the surface of the 
ground, but often the roots also were gnawed through. The land 
was covered with long grass, ferns, etc.. which furnished abundant 
shelter for voles. b During the winter of 1813-14 more than 30.000 
mice by actual count were destroyed in Dean Forest and 11,500 in 
Xew Forest. It was calculated that the total killed by all the 
agencies employed was probably double these numbers. The total 
number of voles killed in both forests during the outbreak was esti- 
mated at 200.000/ 
In the past. American forestry has concerned itself chiefly with 
efforts at conservation, but forest extension has progressed far 
o On June 22. 1907, the number of apple trees alive in this orchard was 22<;. 
The dead trees numbered 154, many of which had succumbed to their injuries 
during the spring of 1007. The trees were thoroughly sprayed with lime-and- 
sulphur wash in November. 1906. and although many meadow mice and some 
rabbits were present, none of the trees were attacked during the succeeding 
winter. 
* Lord Glenbervie's Account, Zool. Journ., vol. I, pp. 438-444. January. 1825, 
c Bell's History of British Quadrupeds, p. 325. 1S74. 
