THE RAT PEST 



3 



overrun and occupy new territory despite 

 the never-ceasing warfare waged against 

 it by man and the competition of other 

 mammals. 



The smaller black rat and roof rat for- 

 merly existed in most parts of the Old 

 World. They preceded the brown rat 

 also in America, but when the latter ar- 

 rived were promptly reduced by it to 

 a secondary position or exterminated. 

 Black rats still exist in some parts of the 

 United States, and roof rats are common 

 with the brown rat in the milder climate 

 of the Southern States. 



IT MAY HAVE TWELVE EITTERS A YEAR 



The greater size of the brown rat read- 

 ily distinguishes it from either of the 

 other species. It averages from one to 

 one and a half pounds in weight and 

 about 18 inches in length. Occasional 

 giants of its kind occur, however, as 

 shown by the capture, near Canterbury, 

 England, of one huge individual weigh- 

 ing over four pounds and measuring 22^4 

 inches in length. 



With an abundant food supply brown 

 rats increase with almost incredible rapid- 

 ity. They have from three to twelve 

 litters a year, each containing from six 

 to more than twenty young, the average 

 being about ten. The young begin to 

 breed when less than three months of age. 



Rats are nocturnal and as a rule keep 

 hidden during the day in holes and other 

 places of concealment about buildings or 

 in burrows which they dig in the ground. 

 Within their retreats they make warm 

 nests of shredded fibrous material, often 

 cut from costly fabrics, in which their 

 naked and helpless young are safely 

 brought forth. 



After careful investigation the United 

 States Public Health Service estimates 

 that the number of rats living under nor- 

 mal conditions in our cities equals the 

 human population, but that in country 

 districts they are relatively three or four 

 times as numerous. 



This estimate is practically the same as 

 that obtained some years ago in Great 

 Britain and Ireland, Denmark, France, 

 and Germany. At intervals, as the result 

 of especially favorable conditions of food 

 supply and weather, extraordinary in- 



creases of rats occur over considerable 

 areas and the damage by them is enor- 

 mously increased. 



A vivid realization of the multitude of 

 rats which thrive as parasites on man's 

 industry may be gained from the results 

 of local campaigns against them. In 1904 

 a plague of rats occurred in Rock Island 

 and Mercer counties, Illinois, and during 

 the month ending April 20 one man killed 

 3,445 on his farm. 



During the campaign of the Public 

 Health Service against the bubonic 

 plague in San Francisco from 1904 to 

 1907, inclusive, more than 800,000 were 

 killed; and in New Orleans, during 1914 

 and 1915, 551,370 were destroyed. 



During the winter and spring of a 

 single year more than 17,000 rats were 

 killed on a rice plantation containing 400 

 acres in Georgia, and by actual count 

 30,000 were killed on another plantation 

 containing about 1,200 acres. On a farm 

 of about 150 acres on Thompson Island, 

 in Boston harbor, 1,300 occupied rat 

 holes were counted and other rats were 

 living about the farm buildings. At a 

 large meat-packing establishment in Chi- 

 cago from 4,000 to 9,000 have been killed 

 yearly. 



AMAZING NUMBERS INEEST GRAIN 

 VESSELS 



: J 



Islands in the tropical or semitropical 

 seas furnish ideal conditions for rats, 

 and in many instances they have in- 

 creased until they have become intoler- 

 able pests, threatening the total ruin of 

 the inhabitants. On one sugar-cane plan- 

 tation in Porto Rico 25,000 rats were 

 killed in less than six months. 



In Jamaica an effort was made to sup- 

 press them by introducing the mongoose, 

 which resulted in the establishment of a 

 second pest. In the Hawaiian Islands 

 the introduction of the mongoose caused 

 the rats to take refuge in the tree-tops, 

 where many of them have nests and have 

 arboreal habits, like squirrels. Wherever 

 present on these islands the mongoose 

 has rendered it exceedingly difficult to 

 raise domestic fowls of any kind. 



As has long been known, rats are very 

 numerous on ships. After the fumiga- 

 tion of a grain vessel at Bombay 1,300 



