THE GROUND SQUIRRELS OF CALIFORNIA. 



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RODENT ERADICATION WORK OF THE BIOLOGICAL SURVEY 



IN CALIFORNIA. 



By F. E. GARLOUCH. 1 



Extensive, persistent and beneficial movements ususally start from 

 small beginnings. The economic work of the Bureau of Biological 

 Survey, United States Department of Agriculture, is an example of this 

 kind. From the experimental operations begun in 1887 in Iowa and 

 Minnesota to determine the economic status of ground squirrels, gophers 

 and certain birds with a view to testing out effective poisons and prac- 

 tical methods for controlling harmful species of birds and mammals, 

 has come the popular nation-wide movement to destroy harmful rodents. 



One or two reasons among several may be mentioned why this control 

 has become necessary. Nature, when not interfered with, tends to 

 establish a balance of numbers in the animal kingdom ; but Nature has 

 not been left undisturbed. Man's activities disarranged things. He 

 killed off the larger animals and birds which prey upon rodents, thereby 

 permitting them to increase out of due proportion and become a serious 

 pest. Natural means of control have thus been reduced and it is now 

 necessary to devise artificial means. Another factor is due to change 

 of habits and preferences of the pests themselves. They have found 

 cultivated grains, fruits and grasses easier to obtain and, in many cases, 

 more to their liking than the wild foods, so they have moved in on 

 fields of the farmer, resulting in great crop losses. 



Experimental work with poisons and traps by several investigators 

 of the Biological Survey on ground squirrels, prairie dogs, pocket 

 gophers, and rabbits was carried on from 1887 until July 1, 1905, when 

 by act of Congress, the Biological Survey was made a bureau and the 

 Division of Economic Ornithology and Mammalogy was established. 

 Since that time the economic work has been continuously and syste- 

 matically going on. The first work was undertaken in California by 

 the survey on pocket gophers in the vicinity of Banning, in Kiverside 

 County, in 1908. The following year experiments were undertaken by 

 S. E. Piper, assistant biologist, to determine an effective method of 

 destroying the California Digger ground squirrel. Space will not 

 permit anything like a full discussion of all of the painstaking investi- 

 gations conducted by him during the next five years. Some of the 

 important results secured and facts learned will suffice. 



Bacterial viruses were tried repeatedly but without satisfactory 

 results. Trapping was found not to be practical on a large scale except 

 for certain animals, and special poisons proved to be the cheapest and 

 quickest way of obtaining desired results. 



POISONS IN GENERAL. 



It may be well to state briefly here some of the general physiological 

 effects of poisons as worked out by various investigators. The effect 

 of a poison may be local, or remote, or the same poison may produce 

 effects both local and remote. By local is meant that the poison directly 



U desire to acknowledge the great obligation to Mr. S. E. Piper and to Mr. W. B. 

 Bell for their suggestions, additions and revision of this article. 



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