14 THE BROWN EAT IN THE UNITED STATES. 



rat are not uncommon. The only albino rats in the collections of 

 the National Museum and the Biological Survey are Mus norvegicus. 

 Black, or melanistic, forms also of the brown sat are known. 



The average measurements of adult specimens of the brown rat 

 in the Biological Survey collections are as follows: Total length 415 

 mm. (16.4 inches); tail 192 mm. (7.1 inches); hind foot 43 mm. (1.7 

 inches). This rat sometimes attains a total length of 19 to 20 inches 

 and has been known to weigh 24 to 28 ounces. The average weight 

 of an adult is less than a pound. 



ABUNDANCE OF RATS. 



Few persons realize the vast numbers of rats that may inhabit a 

 very small area. In cities, particularly, the animals swarm along 

 river fronts and wharfs, as well as in sewers, stables, warehouses, 

 markets, and other places where food is abundant. It is only when 

 some of these harbors are demolished that the real numbers of the 

 rats are discovered. 



The number of rats that may harbor on an ordinary farm is as- 

 tounding. In 1901 an estate of 2,000 acres near Chichester, England, 

 was badly infested with the pests. They were systematically de- 

 stroyed by traps, poisons, and ferrets. The total number destroyed 

 under the personal supervision of the owner was 31,981; while it 

 was estimated that tenants at the thrashing had killed fully 5,000 

 more. Even then the property was by no means free from rats. a 



During the plague of rats on the island of Jamaica in 1833, the 

 number killed on a single plantation in a year was 38,000. The 

 injury to sugar cane on the island by the animals was at that time 

 estimated at half a million dollars a year. b 



An idea of the immense number of rats that may infest a country 

 may be obtained from the report of the Indian Famine Commission 

 presented to the English Parliament in 1881. An extraordinary 

 plague of the animals infested the southern Deccan and Mahratta 

 districts of India. The autumn crop of 1878 and the spring crop of 

 1879 were both below the average, and a great portion of the product 

 was destroyed by rats. Rewards were paid for the destruction of the 

 pests, and over 12,000,000 were killed. While they were mostly 

 of the black species, the illustration of abundance applies just as 

 well to the brown rat, which is even more prolific. 



HABITS OF RATS. 



Close observation of the habits of wild rodents, especially of those 

 chiefly nocturnal, is difficult. It is not surprising, therefore, that 



a The Field (London), vol. 100, p. 545, 1902. 

 &New England Farmer, vol. 12, p. 315, 1834. 

 c British Medical Journal, September 16, 1905, p. 623. 



