ORIGINAL PAPER The trans-boundary importance of artificial bat hibernacula in managed European forests Christian C. Voigt • Linn S. Lehnert • Ana G. Popa-Lisseanu • Mateusz Ciechanowski • Pe ´ter Esto ´k • Florian Gloza-Rausch • Tama ´s Go ¨rfo ¨l • Matthias Go ¨ttsche • Carsten Harrje • Meike Ho ¨tzel • Tobias Teige • Reiner Wohlgemuth • Stephanie Kramer-Schadt Received: 13 October 2013 / Accepted: 4 January 2014 Ó Springer Science+Business Media Dordrecht 2014 Abstract Many European migratory bat species hibernate in large hollow trees, a decreasing resource in present day silviculture. Here, we report on the importance of man- made hibernacula to support trans-boundary populations of noctule bats (Nyctalus noctu- la), a species that performs seasonal long distance movements throughout Europe. In winter, we surveyed nine bat roosts (eight artificial and one natural) in Germany and collected small tufts of fur from a total of 608 individuals. We then measured the stable isotope ratios of the non-exchangeable hydrogen in fur keratin and estimated the origin of migrants using a refined isoscape origin model that included information on expected flight distances and migration directions. According to the stable isotope signature, 78 % of hibernating bats originated from local populations. The remaining 22 % of hibernacula occupants originated from distant populations, mostly from places in northern or eastern countries such as Sweden, Poland and Baltic countries. Our results confirm that many noctule bats cross one or several political borders during migration. Data on the breeding origin of hibernating noctule bats also suggest that artificial roosts may not only be Mateusz Ciechanowski, Pe ´ter Esto ´k, Florian Gloza-Rausch, Tama ´s Go ¨rfo ¨l, Matthias Go ¨ttsche, Carsten Harrje, Meike Ho ¨tzel, Tobias Teige and Reiner Wohlgemuth in alphabetical order C. C. Voigt (&)  L. S. Lehnert  A. G. Popa-Lisseanu  T. Teige  S. Kramer-Schadt Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, 10315 Berlin, Germany e-mail: voigt@izw-berlin.de M. Ciechanowski Department of Vertebrate Ecology and Zoology, University of Gdan ´sk, ul. Wita Stwosza 59, 80-308 Gdan ´sk, Poland P. Esto ´k Department of Zoology, Eszterha ´zy Ka ´roly College, Eszterha ´zy te ´r 1, Eger 3300, Hungary F. Gloza-Rausch Noctalis, Fledermauszentrum GmbH, Oderbergerstr. 27, 23795 Bad Segeberg, Germany T. Go ¨rfo ¨l Department of Zoology, Hungarian Natural History Museum, Baross u. 13, Budapest 1088, Hungary 123 Biodivers Conserv DOI 10.1007/s10531-014-0620-y