POPULATION FLUCTUATIONS AND HABITAT SELECTION IN THE EURASIAN RED SQUIRREL SCIURUS-VULGARIS

The population fluctuations of Eurasian red squirrel Sciurus vulgaris during ten winters showed a strong relation to Norway spruce Picea abies cone crop one year before. Neither, Scots pine Pinus sylvestris cone crop nor mean temperature in December and January had an additional significant effect on the fluctuations. The one-year time-lag between the good spruce cone crop and increased red squirrel density suggests that the rich food supply first increase the winter survival and then the reproductive success. The highest density-index of red squirrels was found in old forest dominated by Norway spruce (mean density-index 34 km-2). This habitat was also occupied in all 10 winters. Other habitats with lower densities were occupied in fewer winters. The variation in density-index was also highest in this habitat indicating that the dispersion of red squirrel individuals in different habitats follow the food supply.