4 



FARMERS^ BULLETIN 896. 



before the Revolution, it has supphmted and nearly exterminated 

 its less robust relative the black rat; and in spite of the constant war- 

 fare of man has extended its range and steadily increased in numbers. 

 Its dominance is due to its great fecundity and its ability to adapt 

 itself to all sorts of surroundings. It breeds (in the middle part of 

 the United States) six or more times a year and produces from 6 to 

 20 young (average 10) in a litter. Females breed Avhen only 3 or 4 

 months old. Thus a pair, breeding uninterruptedly and without 

 deaths, could in three years (18 generations) produce a posterity of 

 359,709,480 individuals. Mice and the black and roof rats produce 

 smaller litters, but the period of gestation, about 21 days, and the 

 number of litters are the same for all. 



Rats and mice are practically omnivorous, feeding upon all kinds 

 of animal and vegetable matter. The brown rat makes its home in 

 the open field, the hedge row, and the river bank, as well as in stone 

 walls, piers, and all kinds of buildings. It destroys grains when 

 newdy planted, while growing, and in the shock, stack, mow, crib, 

 granary, mill, elevator, or ship's hold, and also in the bin and feed 

 trough. It invades store and warehouse and destroys furs, laces, 

 silks, carpets, leather goods, and groceries. It attacks fruits, vege- 

 tables, and meats in the markets, and destroys by pollution ten times 

 as much as it actually eats. It destroys eggs and young poultry, and 

 eats»the eggs and young of song and game birds. It carries disease 

 germs from house to house and bubonic plague from city to city. 

 It causes disastrous conflagrations; floods houses by gnawing lead 

 water pipes; ruins artificial ponds and embankments by burro Aving; 

 and damages foundations, floors, doors, and furnishings of dwellings. 



Unlike the brown rat the black rat rarely migrates to the fields. 

 It has disappeared from most parts of the Northern States, but is 

 occasionally found in remote villages or farms. At our seaports it 

 frequently arrives on ships from abroad, but seldom becomes very 

 numerous. The roof rat is common in many parts of the South, 

 where it is a persistent pest in cane and rice fields. It maintains 

 itself against the brown rat partly because of its habit of living in 

 trees. The common house mouse by no means confines its activities 

 to the inside of buildings, but is often found in open fields, where its 

 depredations in shock and stack are well known. 



Not only are mice and rats, especially the brown rat, a cause of 

 destruction and damage to property, but they are also a constant 

 menace to the health of man. It has been proved that they are the 

 chief means of perpetuating and transmitting bubonic plague and 

 that they play important roles in conveying other diseases to human 

 beings. They are parasites, without redeeming characteristics, and 

 should everywhere be routed and destroyed. 



