22 



Rats and Mice 



circumstances, succeed in overrunning the whole country in the 

 space of a very few years, and how these animals speedily develop 

 into a most serious pest when what may be called the rat resistance 

 of a country is allowed to sink to a low degree. 



In 1909 Boelter, after a long series of enquiries, assumed the 

 density of the rat population to be not less than one rat to each 

 acre cultivated, or alternatively one rat per head of the human 

 population. The minimum number of rats inhabiting Britain was 

 therefore put by him at 40,000,000. In the opinion of many, 

 including the present writer, that estimate is a very low one. 



Between 1909 and 1916 energetic efforts for the destruction of 

 rats were made by many public bodies and companies throughout 

 the country. One metropolitan body, for instance, by trapping 

 and other means, destroyed in 1911, 9,936; 1912, 10,834; 1913, 

 13,781; 1914, 12,616; 1915, 11,272; and in 1916, 15,123 rats; 

 in addition many others not identified must have been destroyed 

 by the official cats kept.* 



The returns published in respect of rats killed in the City and 

 Port of Liverpool afford similar reading. Here again — and 

 numerous other instances could be quoted — the numbers of rats 

 killed from year to year increase rather than diminish. In purely 

 rural districts it is similar : thus in East Haddington the efforts of 

 the Eastern District Committee of the Haddingtonshire County 

 Council resulted in the destruction of rats as follows : — 



For the year ending Oct. 25, 1913 . . 20,798 



24, 1914 . . 23,625 

 23, 1915 . . 25,636 



* Dr. Willoughby has records of the destruction of 931, 8i6 rats between the 

 years 1901 and 1916 ; this number includes rats killed during the voyages or 

 on the fumigation of vessels entering the Thames, as well as those killed in 

 docks and warehouses. He says {in Hit. to the writer) : — " I am not aware of 

 increase [in rat population] in any part of the Port Sanitary District, but 

 suspect it in a few food-store localities which have come into use since the 

 war. ... I suspect that the Brown Eat is found in less numbers than the 

 Black in certain docks, which I recognize as storage or warehouse docks (as 

 opposed to transit docks), from the fact that a larger number of Black than 

 Brown are brought for examination from these docks. In one dock the 

 proportion of Brown to Black brought for examination in 1916 was Brown 

 1,265, Black 90; in another, Brown 249, Black 311. In the one dock the 

 ' wild ' and ' transit ' conditions prevail, in the other the ' warehouse ' and 

 * domestic ' conditions. In the one are grass banks (for summer burrowing) 

 and one-storey sheds ; in the other granite and warehouses. In the Blacks of 

 the above figures I have included raitus and alexandrmus (a fair sprinkling of 

 the latter are reported)." 



