RODENT EXTERMINATION. 



By Passed Asst. Surg. WILLIAM COLBY RUCKER, 

 United States Public Health and Marine- Hospital Service. 



It should be remembered that rodents are extremely wily creatures 

 and that any campaign against them is a contest between the wit of 

 man on the one hand and acute animal instinct on the other. The 

 rat, by his constant association with man, has become extremely 

 wary, and is frightened by anything in the least out of the ordinary. 

 They will eat the bread on which poison is spread so carefully that 

 they will leave behind the poison and take practically all the bread; 

 they will open traps by pressing down the pan, and they have been 

 known to repeat this operation several times within an hour, entering 

 the trap, eating the bait, and then liberating themselves. At other 

 times they will enter the trap and stand on the pan with their hind 

 legs, eat the cheese, then carefully turn around and back out. This, 

 of course, is not possible with snap traps, but they have been known 

 to spring them by causing pieces of wood to fall upon them, after 

 which the bait would be eaten. Rats are found wherever food exists 

 in abundance or where they can find suitable breeding and nesting 

 places. 



Rodent extermination is a problem, with difficulties arising from 

 the animal's highly developed regard for self-preservation. In main, 

 the rat requires two conditions for life. He needs plentiful food and 

 places suitable for nesting and breeding. Eliminate either of these 

 elements and you drive away your rats. Yet the problem remains 

 far more difficult than shown in the simple terms of the above equa- 

 tion. The fabulous speed at which rats multiply will baffle all but 

 the most determined and efficient efforts to exterminate them. Under 

 normal conditions each female bears 3'litters a year and each litter 

 produces 10 young. Under conditions ideally favorable, it has been 

 computed that l.pair of rats will in five years, providing all can live 

 so long, increase to 940,369,969,152. Such a result is, of course, im- 

 possible in nature, for it means that every rat born of the original 

 pair survive five years; that every litter of 10 contains 5 males and 5 

 females; and that the ideally favorable conditions persist. On the 

 other hand, rodent existence is an unending struggle in which an enor- 



(153) 



