ANIMAL COMPETITORS 
CHAPTER I 
THE PEST OF RATS 
WE have in the United States three foreign 
rats, all injurious to health and property. 
1. The brown house-rat (Mus norvegicus), 
called also gray rat, house-rat, barn-rat, 
wharf-rat and Norway rat, and, in England, 
Hanoverian rat. Its average total length is 
about 16.4 inches, of which 7 inches belongs to 
the tail, and it usually weighs less than a pound, 
though. specimens have been known so much 
larger as to weigh 24 to 28 ounces. The gen- 
eral color is grayish-brown above and whitish 
below, the long overhairs of the back having 
black tips. The head is shorter, the muzzle 
more blunt, the ears smaller and the tail rela- 
tively shorter than in the other species. It is 
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