THE BROWN OR COMMON RAT 625 



The rat flourishes on a shore diet. It thus manages to 

 subsist on many of the smaller islands, as on Ailsa Craig, 

 where it arrived in 1889, and eats the innumerable dead bodies 

 of sea-birds falling to the bases of the cliffs.^ 



As a rule rats do not directly molest large animals, but 

 they have been occasionally known to attack or kill men ^ or 

 children,* and to gnaw the feet of elephants in the Zoological 

 Gardens.* Their tendency to cannibalism is interesting in 

 view of the fact that, as described above, they are at ordinary 

 times friendly to all members of their species. Either they 

 run amuck sometimes, or else they attack each other through 

 some mistaken sense of injury.^ Stories of rats eating each 

 other when left over night in cages cannot be regarded as 

 instances of their normal habits, since their sufferings from 

 thirst and hunger probably madden them, and may lead them to 

 connect their troubles with their comrades, as many " game " 

 animals do when wounded by a shot from an unseen hunter. 



Extraordinary calculations have been made as to the 

 damage done by rats and the rate of their increase. F. von 

 Fischer" calculated that a single pair might leave, after ten 

 years, a progeny of 48,319,698,843,030,344,720 rats. 



Mr Lantz '' calculates that in nine generations a single pair 

 of rats would, if breeding uninterruptedly, produce more than 

 twenty million individuals, but such a calculation is entirely 

 theoretical. However, as he states that the average quantity 

 of grain consumed by an adult or half-grown rat is fully 2 

 ounces daily, or 45 to 50 lbs. a year, the average cost for 

 feeding one rat for a year becomes about seven shillings and 

 sixpence. If fed on meat, the cost would be higher, but the 

 calculation is complicated by the fact that rats eat much waste 

 products and, on the other hand, damage more than they eat. 

 Many rats must each destroy fully five shillings' worth of 



' Boyd Watt, Ann. Scott. N.H., 1892, 132. 



^ In Walker Colliery, Killingworth,jfi/« Robert Stephenson, M.P. (the distinguished 

 engineer), quoted by Tomes in Bell, ed. 2, 311 ; see also Millais, ii., 229. 



' Shipley, fourn. Econ. Biol., iii., 1908, 65. 



* Frank Buckland, Curiosities Nat. Hist., i., 76 ; and Millais, ii., 229. 



^ Such highly " civilised " animals as dogs occasionally murder each other when 

 confined together in numbers. 



" Zool. Garten, 1872, 125. ' Lantz, op. cit, 16. 



