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TE^S DEPARTMENT OF THE INTERIOR 

 ISH AND WILDLIFE SERVICE 

 WASHINGTON 25, D. C. 



Leaflet WL - 337 

 January 1952 



ARACTERISTICS OF COMMON RODENTICIDES 



Research and experience, over the years, have thus far failed to produce a rat 

 poison that is universally effective, one that meets all requirements under all conditions. 

 A number are quite useful; most have one shortcoming or another. A rodent-control 

 investigator or operator finds it necessary to be familiar -with the characteristics of all 

 useful poisons in order to select the one - or series - that best fits each particular 

 circumstance. Such factors as toxicity, dosage levels, and relative effectiveness are 

 obviously important. Less often considered, but of equal importance, are degrees of 

 acceptance and reacceptance and the development of tolerances. Odor and taste may be 

 considerations in some instances. Solubility of the material has a definite bearing on 

 bait mixing techniques. Safety precautions are an essential part of any procedure, 

 requiring attention to hazards to the user as well as to humans and animals that might 

 come into contact with exposed baits. The appended table is an attempt to classify the 

 common rodenticides so that they can easily be compared for these purposes. 



It is obvious that full justice cannot be given to some of the categories in the 

 abbreviated space allowed in the tabulation; many do not lend themselves readily to one 

 word descriptions. Although an effort was made to qualify noteworthy variations with 

 footnotes, minute and technical differences had to be sacrificed for the sake of brevity. 

 For example, the degree of hazard existing when a poison is used is purely empirical 

 unless it can be assumed that normal precautions will be followed. The term "antidote" 

 actually means the counteracting of an effect, whereas most so-called antidotes of 

 economic poisons are in reality first-aid treatments, followed by palliatives and sedatives. 

 The statements listed in that column are simply abbreviated descriptions and are not 

 intended as complete directions. The differences between solutions and suspensions and 

 between different types of oils have led to a simple listing of whichever material serves a 

 useful purpose in bait mixing; even then some qualifications are necessary and occasional 

 variations in technique have to be ignored. 



Not all animals react alike. Even within the same species some individuals are 

 considerably more resistant to toxic effects than the average. Some effects vary with 

 seasons, age classes, diet, and even with sexes. Dosage levels are usually calculated 

 to include the bulk of the above -average resistant animals. It is essential to understand 

 that no value accrues from increasing those levels. Such practice is doubly objectionable, 

 for acceptance is usually decreased while the hazard to other larger animals is greatly 

 increased. All that is accomplished is doubling the cost of the bait. Continued re -use of 

 the same poison in the same location, except as noted below, generally results in a decline 

 in acceptance, bait shyness, and poor control. Poisons highly effective in one place are 

 sometimes less effective in adjacent properties. A thorough knowledge of the materials 

 available will assist in overcoming these problems. 



