HABITAT USE, HOME-RANGE AND ACTIVITY PATTERN OF THE NORTHERN BAT, EPTESICUS-NILSSONI, IN A HEMIBOREAL CONIFEROUS FOREST

The northern bat, Eptesicus nilssoni, is one of the very few bat species adapted to hemiboreal coniferous forests, where insect abundance is low. To analyse factors behind this adaptation a colony of the northern bat was studied in a coniferous area in the province of Uppland, central Sweden. The purpose was to investigate habitat use and to analyse how food abundance and reproductive status affect the choice of foraging area and activity pattern. The bats were marked individually with reflective tape and with radiotransmitters. Insect abundance was estimated by using Malaise traps located in different habitats. Most of the time the bats hunted close to the colony (within 600 m) and the most important habitats were lakes and wetlands. However, when insect abundance decreased they shifted to hunting sites far from the colony (4-5 km). After weaning, they flew 20-30 km to visit deciduous woodland and eutrophic lakes.