SQUIRI^ELS, BEAVERS, DORMICE, AND RATS 251 



The fecundity of the Field Vole in favourable seasons is so 

 remarkable that it constitutes a plague seriously affecting human 

 interests. In normal seasons this Rodent has as many as four 

 broods in the year between March and October, and each brood 

 contains from four to six young. A closely allied species on the 

 Continent may produce six different litters in a single season, 

 some of these litters containing as many as eight offspring. A 

 mild winter is necessary as a precedent to one of those special 

 outbursts of fecundity which suddenly people districts of Scotland, 

 England, and Germany with hundreds of thousands of field 

 voles. Without the intervention of man it is probable that this 

 rapid increase of a Rodent would receive counter-checks in many 

 directions, but would nevertheless profoundly affect the develop- 

 ment of other animals. In the first place it has been noticed tliat 

 one of these gipfantic swarms of field voles will so exhaust all the 

 vegetable food within its residential area that a large proportion 

 of its members will die of starvation or will engender some 

 microbe of disease that diminishes the swarm by half. Then it 

 would lead to the proportionate increase and prosperity of owls, 

 hawks, buzzards, weasels, stoats, crows, ravens, and foxes, so that 

 the uninteresting and unpicturesque little vole might be the 

 means of adding hugely to the attractiveness of the local fauna 

 by encouraging these scarcer, larger, handsomer, and more 

 interesting beasts and birds. But man generally steps in and 

 destroys the voles by poison and traps, and with equal zest 

 destroys the owls, crows, hawks, and weasels that have been 

 endeavouring to abate the plague, and the presence of which 

 would have rendered the country so much more attractive to the 

 eye. The extravagant increase of field voles in Scotland or 

 England (the animal is not found in Ireland) has never reached 

 to the dimensions of the same plague in Germany, but it is 

 calculated that occasionally on the borderlands of Scotland and 

 England (about the Cheviots), or in former centuries in Essex, the 

 field vole has suddenly appeared "swarming in millions." On 

 these occasions they may kill a thousand birch trees in one district 

 through gnawing away their bark, or they may cause many sheep 



