4 ANIMAL COMPETITORS 



spread all over the continent, except the Utah 

 basin. 



2. The black rat (Mus rattus), smaller than 

 the brown rat, and sooty or slaty black, paler 

 on the under parts. Like the brown rat, it 

 is of Oriental origin and seems to have pre- 

 ceded the former in its immigration into 

 western Europe and thence to this continent. 

 It was carried from Europe to Spanish Amer- 

 ica about three and a half centuries ago, and 

 thence spread northward to the English col- 

 onies. Upon the arrival of the brown rat in 

 North America toward the end of the 18th 

 century it began to decrease, and is now rare, 

 surviving only in scattered colonies, but re- 

 main numerous in many parts of the West 

 Indies, Middle and South America, Hawaii, 

 etc. 



3. The roof-rat (Mus alexandrinus), simi- 

 lar to the brown rat in form and habits, but 

 grayer above, and yellowish white on the feet 

 and abdomen. Its history is much like that of 

 the black rat, but it has held its own better 

 against the dominance of the brown rat, in- 

 habits sea-going ships, and has established 



