HABITAT UTILIZATION IN SUBPOPULATIONS OF THE RED SQUIRREL (SCIURUS-VULGARIS L, 1758)

Abstract

Three squirrel subpopulations were studied during a period of 35 months. The study areas were located in a commercial forest area of the western Wiehengebirge close to Osnabruck. The investigation was divided into a free range and a laboratory part. The squirrels were marked with a radio transmitter which was fixed around the neck. Thus the animals could be observed individually through periods between 3 and 12 months. The aim was to compare the ranges used by the squirrels in a large continuous forest area and in 2 isolated forest areas each of approximately 20 ha in size. The basis for this examination was the size of the home range and the core area by looking at the interindividual differences and those between groups. The mean home range size in the continuous forest was 11.1 ha (Concave Polygon Method), the average size of the core areas was 1.8 ha (Harmonic Mean Transformation). The mean home range size in the forest islands was 2.4 and 2.6 ha, the average size of the core areas 0.4 and 0.8 ha. The overlapping of home ranges was significantly higher in the forest islands than in the continuous forest. With the exception of 2 squirrels, female and male squirrels utilized their core habitats exclusively. Overlapping between home ranges could be seen for males and females. The number and location of the dreys was noted in the continuous forest. The average number of dreys per animal was 11. In winter the squirrels mostly used dreys in spruce trees. They were built close to the trunk. In summer, in contrast, they used dreys in pine trees. Here, they were mostly located in the branches. The whole day observations of these animals showed that there were differences in the tree species they used: the squirrels which preferred pine trees spent more time feeding and had shorter resting periods than those which preferred spruce seeds. The `'spruce squirrels'' had larger home ranges which they used more selectively for feeding while, the `'pine squirrels'' had smaller home ranges which they used more continuously. The animals in the Forest islands showed a more intense utilization of the home range, the core areas were larger compared to those of the squirrels in the continuous forest.