A Novel Approach to the Investigation of Microclimatic Conditions for Bat Hibernation

A Novel Approach to the Investigation of Microclimatic Conditions for Bat Hibernation

Ralf Gyselings1, Luc De Bruyn1,2, Lucinda Kirckpatrick2, Ben Van der Wijden2, Filip Borms3,4, Grzegorz Apoznański5 and Tomasz Kokurewicz5

1 Research Institute for Nature and Forest, Flemish Government, Brussels, BEL;2 Evolutionary Ecology Group, Departement of Biology, University of Antwerp, Antwerp, BEL;3 Bat Working Group, Natuurpunt, Mechelen, BEL;4 Gotham Nature and Chiropterological Research, Kalmthout, BEL;5 Wrocław University of Environment and Life Sciences, Institute of Biology, Department of Vertebrate Ecology and Paleontology, Wrocław, POL

Knowledge about the temperature and humidity at which bats hibernate is important for a proper conservation and management of bat hibernacula. However, data published in the literature are highly variable and not always consistent. Most published data are based on single measurements during bat surveys, not taking into account seasonal effects. However, seasonal change in conditions however can be of high importance. We used temperature and humidity loggers to investigate these variables in different types of hibernacula, ranging from small bunkers, old military fortresses to a large underground system, in Belgium and in Poland. We combined this data with different bat censuses undertaken throughout the hibernation season and developed a transfer function model to analyze the time series. Temperature in the hibernaculum is modeled as a function of the outside conditions time series and the system properties that influence the dynamics of its internal climate (insulation and air flow). To our knowledge, no such models have been used for bat hibernacula so far. We show that this approach, that takes into account the seasonality and the dynamics of the system, gives a better understanding of bat hibernation preferences. Furthermore, we present a number of case studies where the transfer function model has been used to design improvements to the hibernacula for a better conservation of hibernating bats. Finally, since the transfer function model depends on system properties and outside conditions, the model can be used to investigate the effect of climate change on bat hibernacula.