12 



that a pair produces only four litters, six in each litter, each 

 rat living three years, he figures that in that time the progeny 

 of one pair would be 651,050.^ In temperate latitudes the 

 brown rat is now known to breed from three to five times each 

 year, bringing forth from six to twenty young each time. 

 Assuming that the animal breeds but three times a year, and 

 produces on the average ten young at each period. Prof. David 

 E. Lantz estimates that with no deaths the number at the end 

 of the third year would reach 20,155,392 individuals.^ Dr. 

 William Colby Rucker, Assistant Surgeon-General, United 

 States Public Health Service, computes the theoretical increase 

 of a pair of rats for five years at 940,369,969,152.' It is hardly 

 necessary to say that such results as these could not occur in 

 nature, but these figures indicate the immense possibilities of 

 this pest under favorable circumstances. Let mankind rejoice 

 that rats are cannibals. 



RAT NUMBERS AND DESTRUCTIVENESS. 



If an exact census of the rats in the United States could be 

 taken, their numbers probably would be beyond belief. 



Few people realize how many rats infest their premises. 

 Possibly there are none in some localities, but there are very 

 many more in existence than ever are seen by human eyes. 

 The number varies from a few pairs on some well-cared-for 

 estates to hundreds in ratty tenements and farm buildings, and 

 thousands on ill-protected farms and country estates. Rats 

 come and go mysteriously in some localities. There are some 

 large areas in the country Where very little grain is raised or 

 used, or where for some other reason rats are not numerous; 

 other regions swarm with them. Farmers or householders, 

 when interrogated, usually admit that they have a few rats. 

 Careful investigation, however, sometimes shows that the 

 farmer suffers an annual loss, equal perhaps to his taxes, be- 

 cause of the grain eaten or wasted by rats in the fields and 

 stolen from his fowls, cattle, horses and hogs, from his stored 

 unthreshed grain, or from barrels and bags in barns or store- 



' Rodnell, James, The Rat, 1858, pp. 167, 168. 



2 Lantz, David E., U. S. Dept. Agr., Biol. Surv. Bull. 33, 1909, p. 16. 



• Treas. Dept., Public Health and Marine Hospital Serv-. of U. S., The Rat and its Relation 

 to the Public Health, by various authors, 1910, p. 153. 



