Spatial and temporal distribution of bats (Chiroptera) in bright summer nights

Most bat species show plasticity in their choice of habitat and landscape. This study focuses on the distribution and activity of bats along the hillsides and onto the shores of a low salinity marine Norwegian fiord at 62°N. Ultrasound was recorded using D500 detectors in June and July at 42 different sites from the shoreline and up the hillsides to around 200 m. Detectors were placed in well-preserved woodlands. Only Pipistrellus sp., northern bats Eptesicus nilssonii and bats of the Myotis genus were common. There was a clear non-linear spatial distribution pattern along these slopes, with a pronounced increase in the number of recorded bats at short distances from the shore. On all six nights, the detector closest to the shore had the highest number of recorded bats. A pattern was also seen in bat distribution over time. Pipistrellus sp., northern bats and Myotis species all had a peak near the shore during the darkest part of the night, which is around 01.35 h in mid-summer at this latitude. At greater distances, Pipistrellus sp. and northern bats had a peak around 40 minutes to one hour before the darkest part of the night, respectively. Here, Myotis spp. peaked about an hour after 01.35.