De cyclus van de Veldmuis Microtus arvalis

The cycle of common voles in Drenthe is being monitored since late 1986, by analysing the contents of pellets of Long-eared Owls. The population low of 1994 and 1995 was apparently continued into 1996 (Fig. 1). However, 1996 was a peak year of the common vole. This was not evident from the pellet analyses, because high densities of Apodemus sylvaticus and Microtus agreslis inflated the proportion of common voles in the diet of Long-eared Owls.