16 



BULLETIN 1023, U. S. DEPARTMENT OF AGRICULTURE. 



In a previous communication (23) it was shown that the average 

 size of the meal consumed by hungry white rats was one one-hun- 

 dredth of their body weight. Good practical poisoning results were 

 obtained with barium carbonate by putting three times the amount 

 necessary to kill (20 per cent) in the bait. If one-third of the 

 average meal were consumed a fatal dose would be ingested. On 

 this basis the efficient percentage of strychnine in a rat bait should 

 be 0.75 per cent, or 1 part in 133 parts of bait. This concentration 

 will be useful in the preparation of baits that are tasteless and rapidly 

 consumed. Practically, however, it may be found that more strych- 

 nine will be required if such baits are not consumed quickly, or if 

 the potency is decreased. 



Table 9 gives a list of baits, worked out by practical tests, which 

 seem to contain a very liberal amount of strychnine for all animals 

 other than the rat. The rat, however, is five or six times more re- 

 sistant to strychnine administered subcutaneously (Table 1) than the 

 ordinary domesticated rabbit. If these data for the domesticated 

 rabbit are representative also for the jack rabbit, the liberality with 

 which this animal has received strychnine in its bait and the short- 

 comings of the rat bait will at once become apparent. The rat baits 

 contain on the average but little more strychnine than the jack rabbit 

 baits. The ground squirrel (Citellus richardsoni) is four or five 

 times more sensitive to strychnine than the rat (Table 8). These 

 animals are killed by relatively much less strychnine because strych- 

 nine is far more potent by way of the cheek pouches than when taken 

 into the stomach. The difference between the concentration of 

 strychnine in the ground squirrel baits and that in the rat baits, 

 however, is not as marked as might be expected. 



Table 9. — Types of strychnine lait used for poisoning animals. 





Strychnine. 



Animal. 



Equivalent or approxi- 

 mate amount of strych- 

 nine sulphate in dry 

 bait. 





Bait. 



Form 



in which 



added. 



Ultimate 

 form. 



Citation. 



Milo maize 



Do 



Do 



Alfalfa 



Milo maize 



Barley 



Sulphate.. 



Alkaloid . . 

 Sulphate. . 



...do 



...do 



S u 1 phate 

 or alka- 

 loid. 

 Sulphate. . 



...do 



...do 



Sulphate.. 



Alkaloid. . 



...do 



...do 



Sulphate.. 



Alkaloid. . 



...do 



Sulphate.. 



Ground squir- 

 rel. 



Prairie dog 



do 



do 



Jack rabbit. . . 

 do 



Ground squir- 

 rel. 

 Rat 



Parts. 



1-480 



1-290 

 1-370 

 1-360 

 1-257 

 1-366 to 1-262 



1-290 



1-170 to 1-210 



1-200 



1 1-100 



Per cent. 

 0.21 



.35 

 .27 

 .28 

 • ,39 



0.3 to 0. 38 



.345 



•0.59 to 0.48 

 2.50 

 3.25 



Merriam (17). 



Bi. 158.< 

 Bi. 158. 

 Bi. 163. 

 Bi. 163. 

 Bi. 163. 



Pierce and Clegg 



(20). 

 Lantz (14). 

 Do. 



Wheat 



do 



Do 



...do 



...do 



do 



Rucker (21). 











1 Somewhat less on moisture basis. 



2 Estimate liberal. 



3 Allowing for presumable typographical error in original article; estimate liberal. 



* " Bi. "refers to mimeographed circular letter giving directions for making baits, issued by the Bureau of 

 Biological Survey, U. S. Department of Agriculture. 



