Species composition, spatial distribution and population dynamics of bats hibernating in Wisłoujście Fortress, Polish Baltic Sea Coast (Chiroptera: Vespertilionidae) [Skład gatunkowy, rozmieszczenie przestrzenne i dynamika populacji nietoperzy zimujących
Konrad Sachanowicz, Agnieszka Przesmycka, Mateusz Ciechanowski
The structure and dynamics of bat assemblage in winter and transitional period was studied in the Wisłoujście Fortress (16th–19th century) located in Gdańsk city, northern Poland. The object was used partially as a commercial store (until 1995), later as a summer tourist attraction, protected in winter from human penetration. Serious threats for existance of this monument forced recently the local officials to the intensive renovation project, leading to deterioration of roosting conditions for bats. In total, nine species were recorded: Myotis myotis, M. nattereri, M. mystacinus, M. brandtii (rare in Pomerania region), M. dasycneme (EN in Poland), M. daubentonii, Eptesicus serotinus, Pipistrellus nathusii (first winter record in Poland) and Plecotus auritus. M. daubentonii predominated among bats counted in autumn (43.4%) and netted in the entrances to the casemates (60%). M. nattereri was the most numerous species during winter (67.3%) and spring censuses (71.0%). M. dasycneme composed 3.5% of all bats counted inside of the Fortress (n=2256 records) but about 18% of individuals captured in mist nets (n=67). Only 8–12 bats were counted during winter 1993/1994. The number of bats increased significantly (r=0.86, p<0.02) until 2005, reaching the total number of 313 individuals in the whole object; however this trend was severely interrupted by restoration works. The adaptation of formerly unprotected roost in the Fortress area (installation of bat grill, walls of air-bricks etc.) compensated this decline only in a limited way. In winter 2002/2003 we studied seasonal dynamics in bats’ numbers. The highest number of M. daubentonii and M. dasycneme was recorded in September. The number of M. nattereri, after a peak in a half of September, declined almost to zero in October and increased again, reaching its maximum value in February. Natura 2000 site was established in the Wisłoujście Fortress, although its future remains uncertain.