THE GRAY RAT. 311 



round. Slow thinkers are slow livers, and there- 

 fore they live long. 



The gray rat has probably not reached le premier 

 Octobre, as the French call it, by the end of the 

 second year of its existence, and the solitary males, 

 driven out from their colonies, are in all likeli- 

 hood living in their fourth or fifth summer. At 

 six years a gray rat would have far outlived the 

 majority of its kind, and I doubt whether the 

 females breed after their third year. These state- 

 ments, however, are based on such scanty observa- 

 tions that they border upon guess-work, and no 

 doubt the whole question is decided by the con- 

 ditions under which the rat lives, which means the 

 rate at which it lives. A female that begins 

 breeding at five weeks old, and thereafter produces 

 five or six litters annually, naturally does not con- 

 tinue to breed so long as one living at a more 

 moderate rate ; and it is probable that the bucks 

 outlive the does, as most of the very old rats 

 caught or observed are bucks. 



DIMENSIONS. 



An adult male rat usually scales about 13 oz., 

 the females from 14 to 16 oz. ; 20 oz. is not a rare 

 weight. The average tip-to-tip measurement of 

 males can be taken as 16 inches, of which the tail 

 accounts for 7 inches. 



