58 \.\" ECONOMIC STUDY OF FIELD MICE. 
Ajnong the mineral poisons thai have been successfully employed 
in destroying field mice is barium carbonate This substance is com- 
paratively cheap, and is both odorless and tasteless, so that rodents 
do not detect its presence in food. Its action in the digestive tract 
of rats and mice is slow, but reasonably sure to produce death. 
Larger animals are not affected by small doses of the poison, such as 
would be put out to kill mice; and for {his reason its use is attended 
with less danger than that of strychnine or arsenic. 
This poison is usually administered in the form of dough made of 
four-fifths flour or meal and one-fifth barium carbonate. A little 
sugar is added to sweeten the mixture, and, if desired, a couple of 
drops of anise oil. The dough is cut into small lumps (the size of a 
large pea) for mice, but larger ones are required for rats. The poison 
may be fed also in moistened bread or oatmeal. 
Although the advantages of barium carbonate as a rodent poison 
have been long known, it has recently been brought into prominence 
on account of successful experiments in destroying field mice with it 
made by Dr. Lorenz Hiltner, of Munich, Germany, and by E. Schri- 
baux in France. 6 
Winter is the most favorable season for poisoning field mice. 
Summer poisoning is usually less successful, on account of the abund- 
ance of green food. Although the animals are active in nearly all 
kinds of weather, they move about more freely in winter when it is 
comparatively warm. For the best results, therefore, poison should 
be set out in the evening of rather mild days. Since mice usually 
work under the snow, it is useless to put out poison for them on the 
surface of the snow. 
The importance of protecting birds during poisoning operations 
can not be too earnestly insisted upon. In France, in 1905, a great 
scarcity of birds, particularly partridges, was noticed in the depart- 
ments of Vienne, Deux-Sevres, and Charente, which was attribute 
to the extensh^e use of poisons during 1904 to destroy field mice 
Says the editor of Western Field, of San Francisco, Cal. : " In tw 
or three counties in this State — notably in that of Santa Barbara — 
the quail, dove, and song birds are being threatened with actual 
extermination from poison put out by farmers with the intent of kill- 
ing off the ground squirrel pests. The poison has been scattered 
indiscriminately over wide areas, and reliable observers keep sending 
in reports of their finding thousands of dead birds of all kinds. 
victims of the squirrel bane." d 
« rraktische Blatter fur Pflanzenbau und Planzenschutz, vol. 1 (new series). 
pp. 112-116, November. 1903. 
6 Journal d' Agriculture Pratique, vol. 9 (new series). Xo. 22, pp. 708-710. 
1905. 
c Journal d'Agriculture Pratique, Sept. 14. 19(>r>, p. 327 (quoting the journal 
Temps). 
''Western Field, vol. 8, Xo. 1, p. 57, February, 1906. 
1 1 
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