THE KINDS OF RATS 75 



In many localities, e.g. Great Yarmouth, and in isolated 

 dwelling-places they occur, and even outnumber the 

 Norwegian rat. A most important and remarkable 

 fact is that the rats which infest ships are often all Black 

 rats. The Black rat, or Alexandrine rat (as Mr. Thomas 

 calls it), lives in our houses, in the roof, in recesses of 

 woodwork. It is a house rat, whereas the Grey, or 

 Norwegian rat, lives in the sewers and the banks of 

 ditches, and only comes up into the basement of houses 

 through defective building. The Grey rat has driven 

 out the water-voles from many river banks near towns, 

 just as he has to a great extent taken the place of the 

 Black rat in houses where the kitchen and food stores 

 are close to and in communication with the sewer ! 



The Black rat cannot be really distinguished by his 

 blackness. That is why some naturalists call him the 

 Alexandrine rat, so as to avoid a misleading implica- 

 tion. He is often of a bright yellowish-brown colour 

 along the back with longer dark-brown hairs and a 

 good deal of grey elsewhere quite like the Norwegian 

 or Grey rat in colour. At the same time he is often 

 blackish, and frequently very black. The colour of all 

 these kinds of rats and mice can vary, according to the 

 conditions and colour surroundings in which they live. 

 Black, white, sandy-brown, or a mixture of spots of all 

 three colours, or a uniform " mouse-brown " tint, are 

 (as most boys know) the possibilities revealed by 

 allowing them to breed in captivity. Nature selects 

 accordingly the particular tint which affords protection 

 from observation by enemies in a given locality. 



The real distinction between the Black (Alexandrine) 

 rat and the Grey (Norwegian) rat is that the Black rat 

 is smaller, has a tail longer than its body (125 per cent.), 

 and long and wide ears, which stand out from the head. 

 The Grey (Norwegian) rat is a larger, heavy-bodied rat, 

 with a tail shorter than its body (90 per cent.), and 

 short ears. Both these rats are common in India, but 



