NICHE SIZE AND NICHE OVERLAP IN THE CHOIC E OF FOOD PLANTS BY RED DEER (CERVUS-ELAPHUS L, 1758) AND ROE DEER (CAPREOLUS-CAPREOLUS L, 1758) IN THE NORTHWEST EIFEL

Niche sizes as measures of the actively used resource spectrum as rega rds the choice of food plants (''the converse of specialization'') wer e determined for wild red and roe deer. A chronological reference syst em based on plant phenology and a spatial reference system founded on plant associations were used to classify data from a 30 km2 investigat ion area in the northwest Eifel into a resource matrix (Table 1). This was then used to calculate niche size and niche overlap (Table 2). Se asonal changes in niche sizes of red deer (Fig. 1) and roe deer (Fig. 2) are closely correlated to seasonal changes in food supply in these spruce dominated habitats as well as to seasonal changes in behaviour. The amount of the resource spectrum used is inversely proportional to the supply. Niche size in the winter increases to a maximum of 2.227 for red deer and 1.794 for roe deer, indicating an expanded utilizatio n of the resource spectrum to meet metabolic needs; or a decreased sel ectivity in the choice of food plants with a decreasing supply of thes e. The minimum niche size coincides with the time of optimum food supp ly, for red deer with 0.450 in early summer. The relative minimum in m id autumn (1.539) for red deer is a result of the synchronization and synlocalization of the population due to the rutting season. Red deer have a higher amplitude in niche size, 1.777, compared to roe deer, 0. 619, reflecting their much greater adaptability in the trophic system as befits a ruminant of intermediate type in comparison to a concentra te selector like roe deer. The results emphasize the fact that the hab itat utilization by red deer limits the food supply for roe deer. The generally low niche overlap values of 0.22-0.88 (Fig. 3), rather, demo nstrate the carrying capacity of the habitats in the sense of compleme ntary utilization, especially in consideration of the present browse s carcity in winter and early spring when values of 0.58 or 0.48 were ca lculated.