REPRODUCTION AND GROWTH IN BANK VOLES CLETHRIONOMYS-GLAREOLUS - THE EFFECT OF FOOD-QUALITY AND DENSITY MANIPULATIONS IN A LABORATORY COLONY

Young laboratory raised bank voles Clethrionomys glareolus, originating from a cyclic population at low phase, were experimentally subjected to manipulations of food and density. This was done to assess possible effects of the juvenile environment on later breeding success. Juveniles were exposed to the experimental treatments for 40 d previous to pairing. The study revealed that a high population density in itself can increase future breeding success as compared to low density. This effect was only found in females. There were also indications that high density led to arrested growth in subordinate females.