58 AN ECONOMIC STUDY OF FIELD MICE. 



Among the mineral poisons that 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 this 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 , a and by E. Schri- 

 baux in France. 7 ' 



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 Yienne, Deux-Sevres, and Charente, which was attributed 

 to the extensive use of poisons during 1904 to destroy field mice. c 



Says the editor of TTestern Field, of San Francisco, Cal. : " In two 

 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 



a Praktische Blatter fur Pflanzenbau und Planzenschutz, vol. 1 (new series), 

 pp. 112-116, November. 1903. 



& Journal d' Agriculture Pratique, vol. 9 (new series), No. 22, pp. 708-710, 

 1905. 



c Journal d' Agriculture Pratique, Sept. 14. 1905, p. 327 (quoting the journal 

 Temps). 



<* Western Field, vol. S, No. 1, p. 57, February, 1906. 



