6o 



Rats and Mice 



5. TABLE SHOWING EATE OF INCREASE IN 

 RAT POPULATION POSSIBLE IN 1918. 



(The calculations are based on the assumptions made on p. 24.) 



The following are the numbers of ixiirs of rats possessing a 

 chance of breeding which might be living at the dates specified, on 

 the assumptions indicated at p. 24 : — 



1918. 



Genera- 

 tion 1. 



Generation 2. 



Jan. 1 







10,000,000^ 



j_jiiLer 1. 

 10,000,000 

 9,208,334 













Feb. 1 

 Mar. 1 



9,208,334 

 8,416,668^ 



Litter 2. 

 8,416,668 

 7,700,000 



7,050,000 











Apr. 1 

 May 1 



June 1 



7,625,000 

 6,833,336^ 



6,041,670 



8,416,668 

 7,625,000 



6,833,336^ 



Litter 3. 



6,833,336 









July 1 

 Aug. 1 



5,250,000^ 

 4,458,338 



6,041,670 

 5,250,000, 



6,400,000 

 5,700,000^ 



6,300,000 

 5,730,000 



Litter 4. 

 5,250,000 







Sept. 1 



3,666,672. 



4,458,338 



5,050,000 



5,200,000 



4,825,000 



Litter 5. 

 3,666,672 





Oct. 1 



2,875,000 



■ 3,666,672^ 



4,400,000^ 



4,650,000^ 



4,400,000 





Nov. 1 



2,083,340g 



2,875,000 



3,750,000 



4,100,000 



4,000,000 



3,370,000 



Litter 6. 

 2,083,340 



Dec. 1 



1,291,674 



2,083,340^ 



3,075,000^ 



8,600,000^ 



3,600,000 



3,080,000 



Dec. 31 



500,000j, 



1,291,674 



2,400,000 



3,050,000 



3,150,000 



2,800,000 



1,900,000 



1918. 



Generation 3. 



Genera- 

 tion 4. 



July 1 

 Aug. 1 

 Sept. 1 

 Oct. 1 

 Nov. 1 



Dec. 1 

 Dec. 31 



Litter la. 



6,833,336 

 6,300,000 

 5,730,000 

 5,200,000 

 4,650,000^ 



4,100,000 

 3,600,000^ 



Litter 16. 

 5,250,000 

 4,825,000 

 4,400,000 



4,000,000 

 3,600,000^^ 



Litter Ic. 

 3,666,672 



3,370,000 

 3,080,000 



Litter 2a. 

 5,700,000 

 5,230,000 

 4,775,000 



4,350,000 

 3,900,000^ 



Litter 26. 

 4,400,000 



4,050,000 

 3,700,000 



Litter 3a. 

 4,650,000 



4,270,000 

 3,900,000 



Litterla-«, 

 4,650,000 

 4,270,000 



















