224 



abandoned the Isle of France (Mauritius) in 1610 because of the great 

 abundance of rats. 



AMOUNT OF LOSSES CAUSED BY RATS. 



The damage done by a single rat varies greatly with the circum- 

 stances. We have already stated that the cost of feeding a rat on 

 grain varies from 60 cents to $2 a year. Assuming that much of 

 the rat's food is waste, each rat on a farm will cause a loss of over 50 

 cents a year. In cities the damage by a single rat probably averages 

 more than in the country. Hotel managers and restaurant keepers 

 state that $5 a year is a low estimate of the loss inflicted by a rat. 

 In making an estimate it should be remembered that the rat is to be 

 charged not only with the food it actually consumes but also with 

 what it destroys or pollutes and renders unfit for use. 



If an accurate census of the rats in the United States were possible, 

 and if the minimum average loss caused by a rat were known, an 

 estimate of the total annual losses from their depredations could be 

 made. It was on such a minimum basis that the Incorporated 

 Society for the Destruction of Vermin arrived at their total estimate 

 of 15,000,000 ($73,000,000) as the yearly losses from rats in Great 

 Britain and Ireland. Three propositions were assumed: first, that 

 in cities and villages the number of rats equals the population; second, 

 that in the country there is at least one rat for every acre of cultivated 

 land; third, that each rat in the kingdom inflicts a damage of at least 

 a farthing per day. Circulars asking whether these assumptions are 

 excessive were distributed throughout the country. From 90 to 99 

 per cent of the replies fully indorsed each of the assumptions. 



It can readily be seen that the English basis of estimate would not 

 apply to farm conditions in the United States, where the area in the 

 twelve leading crops alone is over 250,000,000 acres. On a basis of 

 a rat per acre and damage of a farthing per day the annual loss on 

 this area would be $450,000,000, a sum much too great for serious 

 consideration. However, in the more thickly populated parts of the 

 country an estimate of one rat per acre would not be excessive; and 

 it is probable that in most of our cities there are quite as many 

 rats as people. Yet it would be unsafe, owing to our vast territory 

 and varying conditions, to make these assumptions the basis for 

 conclusions. 



Over a year ago the writer made an attempt to investigate actual 

 conditions, and thus arrive at an estimate of the total damage by rats 

 in the cities of Washington and Baltimore. From the data obtained 

 the direct annual damage in the two cities was calculated at $400,000 

 and $700,000, respectively. The Census Bureau in 1906 estimated 



a Chambers's Journal, vol. 21, p. 244, 1854. 



