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 have 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 
1 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. 
2 A. H. Cocks, Bucks. 
° Cocks says this is so if there are not fewer than three rats present. 
VOL. II. 2R 2 
