Trophic Relationships of the Common Vole in Cultivated Fields*

On the area of 3,100 ha of cultivated fields the density of the fol-lowing species of rodents was estimated: M. arvalis in fields and C. glareolus, A. flavicollis and A. agrarius in woods. At the same time the numbers of predatory nammals and birds were estimated. During the whole period of study in area under examination 3,400,000 individuals of M. arvalis and 43,000 of forest rodents were present. Between the depression and the peak of numbers the density of M. arvalis increased over one hundred- times. At the density of 44 individuals/ha the voles consumed in a year 79 kg d.w. of alfa-alfa/ha, and at 774 indiv./ha as much as 1,153 kg d.w./ha. It was demonstrated that the ratio of plant weight destroyed to consumed amounted in alfa-alfa cultures to 1.8:1. At a low density c\f M. arvalis considerable losses of winter rye during winter are compensated by the regrowth of plants in spring. Food requirement of predators was determined and their diet in field conditions was investigated. The highest number of M. arvali