THE BROWN OR COMMON RAT 621 



Without being specialists, they are excellent climbers, so 

 that it is difficult to imagine a situation to which they could 

 not penetrate. Barrett- Hamilton (MS.) says, "My own home 

 is rat-proof as regards the basement, but a constant watch and 

 ward is still necessary to keep rats from entering by open doors 

 and windows, and they hiave several times, by climbing up the 

 walls, found their way to the roof. In climbing, the tail is used 

 as a balancing organ, and to a very small extent tends to be 

 prehensile, especially when the animal is descending, oppor- 

 tunity being taken to twine it round any available object."^ 



One of the chief factors leading to the success of rats is 

 their excellent social system. Although the old males seem to 

 live apart ^ in special burrows of somewhat simple construction, 

 the bulk of the species are eminently sociable animals, not 

 separated off in mutually exclusive clans like Water Rats. 

 This is shown when one is introduced into a receptacle contain- 

 ing other rats. Unless one be wounded no objection is raised 

 to the arrival of the new-comer, who, although a stranger, is 

 invariably received as a comrade. Perhaps for this reason a man 

 can insert his hand amongst a lot of caged rats and handle 

 them without fear of being bitten ; ^ and where a rat is killed 

 its place is rapidly occupied by another so long as any trace of 

 the original one remains, either by way of smell or otherwise. 

 Similarly in a garden one may grow tulips for years without 

 their being discovered by rats. Should, however, one rat 

 discover and dig for the bulbs, it is little use trapping him, for 

 every rat that passes will be attracted by the " signs " of its 

 predecessor. They are diabolically intelligent animals, and 

 where a bed in a garden has been recently dug over, will 

 excavate anything planted in it, apparently for the sake of 

 curiosity. 



So intelligent are these animals, that they are believed to 

 resort to combination for the attainment of a desirable object, 

 as when two assisted each other to push a dog-biscuit through 



' Cf. Millais (ii., 181), who points out that in the Dormouse the tail is only a 

 balancer ; in rats and mice it is almost prehensile ; while in the Harvest Mouse it is 

 specialised for prehension. 



^ A. H. Cocks, Bucks. 



' Cocks says this is so if there are not fewer than three rats present. 



VOL. II. 2 R 2 



