196 ANNALS OF SCOTTISH NATURAL HISTORY 



voles multiplied till everything green was eaten, and the 

 whole herbage destroyed ; being cut at the roots, and lying 

 on the ground like withered hay. No attempt was made to 

 burrow in that description of ground, which is more or less 

 damp, except in the drier areas. Here shelter was sought 

 among the large tussocks of withered herbage, in shallow 

 runs over the surface, and along the sides of the surface 

 drains. But on the firmer ground, where the vegetation was 

 not luxuriant, burrows were made six to fourteen inches deep. 

 After a time, rain and wind levelled the tussocks ; and con- 

 siderable tracts of the grass were burnt with the view of lessen- 

 ing the cover. Then, food and shelter having disappeared, the 

 areas first occupied were deserted, and the animal appeared 

 in greater numbers upon ground on which it had not been 

 previously numerous, and on the " heights," which, over most 

 of the southern highlands, are covered with vegetation. 

 From these resorts it made its final disappearance. 



So far as can be ascertained, the disappearance has been 

 general over the whole infested area. On some farms, the 

 normal numbers remain, on others scarcely a vole is to be 

 seen. 



The question arises, To what causes can be ascribed a 

 result so complete and so satisfactory ? Inquiry has been 

 made as to the effect of the weather during the decline of 

 the plague, the possibility of the occurrence of an epidemic, 

 and the action of natural enemies. 



As regards weather, the summer of 1892 was cold and 

 cheerless, followed by a wet autumn, when the decrease 

 began. A severe frost set in before Christmas, which lasted 

 till February. That frost was succeeded by an exceptionally 

 genial spring. The general opinion of the farmers and 

 shepherds communicated with is, that the state of the weather 

 appeared to have nothing to do with the disappearance. 

 But one or two farmers whose views are entitled to considera- 

 tion point out that the animal was partial to damp ground, 

 and consider that the exceptional drought of last winter and 

 spring had an effect. All, however, w T ith one exception, agree 

 that the frost of last winter had no effect, though it was 

 severe, and though unaccompanied by much snow. 



Turning to the possibility of an epidemic, it has been 



