Family MURIDAE 185 



The Norway rat is truly omnivorous. It eats the kinds of 

 foods consumed by man and many other things besides. An adult 

 rat usually requires a minimum of Y\ ounce of dry food and 

 Yi to 1 ounce of water daily. 



This rat is able to enter buildings by climbing wires or faces 

 of rough walls, by gnawing through wood, or by burrowing 

 under masonry foundations. 



In most years the citizens of Illinois are the custodians of 

 about one Norway rat per person. A rat that lives near sup- 

 plies of food for man or livestock eats, fouls, or otherwise 

 wastes more than 20 pounds of food or feed each year. Also it 

 undermines foundations and damages wooden structures by its 

 burrowing and gnawing. 



In the wild, the Norway rat is preyed upon by foxes, weasels, 

 minks, owls, hawks, snakes, and other animals. In urban dis- 

 tricts and around farm buildings, man can be its worst enemy. 



Signs. — The Norway rat makes tracks, fig. 22, that are like 

 those of a tree squirrel, but the prints of the front feet are 

 smaller and less often paired; also, a tail mark often shows. 

 Droppings are oblong and usually up to Y inch long. A dark 

 smudge along a baseboard molding or around a hole in a wall or 

 floor is indicative of a frequently used path of a rat. A burrow 

 of this rat has piles of dirt and often corncobs or pieces of junk 

 at the entrance. Gnawed doorways, fig. 100, are common in 

 poorly sanitated sections of cities. 



Distribution. — The Norway rat is abundant throughout 

 Illinois. Only the subspecies Rattus norvegicas norvegiais 

 (Berkenhout) is known in the United States. The Norway rat 

 occurs in southern Canada, along the Pacific Coast to northern 

 Alaska, and throughout the United States and Mexico. 



MUS MUSCULUS Linnaeus 

 House Mouse 



Description. — The house mouse, fig. 101, is grayish brown 

 to dark gray on the upper parts and gray or buff on the under 

 parts. Its practically hairless tail is uniformly brownish gray. 



Albinos of this species are the ''white mice" of laboratories. 



Length measurements: head and body 2^-3^ inches (70-85 

 mm.) ; tail 2^-3^4 inches (60-95 mm.) ; over-all 5-7 inches 

 (130-180 mm.); hind foot Ys~Y inch (16-19 mm.). 



