Environmental variables do not explain the high size fluctuations in Rhinolophus euryale pre-hibernating aggregation
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ORIGINAL ARTICLE
Environmental variables do not explain the high size fluctuations in Rhinolophus euryale pre-hibernating aggregation Marcel Uhrin 1
&
Mária Sabolíková 1 & Ladislav Naďo 2 & Edita Maxinová 1
Received: 28 May 2019 / Accepted: 21 January 2020 # Institute of Zoology, Slovak Academy of Sciences 2020
Abstract The Mediterranean horseshoe bat, Rhinolophus euryale, creates in the pre-hibernation period an aggregation in the Domica cave (Slovakia) and despite the harsh winter conditions displays a certain amount of flying activity. The goal of the study was to find out whether some environmental factors influence these conspicuous aggregation dynamics. We used image and statistical analysis of pictures of the aggregation taken automatically in the cave along with atmospheric pressure, humidity, outside and inside cave temperature and oxygen and carbon dioxide contents in the cave. These environmental variables were assumed to explain the observed activity. We hypothesised that the number of bats in particular time periods would correlate with some of these variables, but this was not confirmed. The only significant relations confirmed were those between bat numbers and humidity and carbon dioxide values in the cave. No trend in the spatial positioning of the bats was observed, and no environmental factors influenced the numbers, movements or groupings of bats. On the contrary, bats by their presence (breathing), activity and production of excrements may significantly influence the microclimate of the cave environment. Keywords Temperature . Humidity . O2 and CO2 content . Air pressure . Image analysis . Slovakia
Introduction Hibernation and the swarming behaviour preceding it are, along with reproduction, among the most important periods in the life cycle of temperate bats. Hibernation is a crucial strategy for surviving the winter periods, when arthropods as their basic prey are less available or fully absent, and living conditions are incompatible for bat life (e.g. Erkert 1982; Ransome 1990; Ruf and Geiser 2015). Nevertheless, hibernation is usually not continuous, and in several bat species various intervals of arousal have been observed, despite the fact that they are probably Electronic supplementary material The online version of this article (https://doi.org/10.2478/s11756-020-00428-8) contains supplementary material, which is available to authorized users. * Marcel Uhrin [email protected] 1
Department of Zoology, Institute of Biology and Ecology, Faculty of Science, Pavol Jozef Šafárik University in Košice, Košice, Slovakia
2
Institute of Forest Ecology, Slovak Academy of Sciences, Zvolen, Slovakia
energetically expensive (Daan 1972; Thomas and Geiser 1997; Lyman et al. 2013). These arousals, evidenced in temperate rhinolophids and vespertilionids, involve various functions, for example, drinking, foraging in and/or outside the hibernaculum, social interactions, or changing hibernation position or even roosts (Avery 1985; Brigham 1987; Hope and Jones 2013; Miková et al. 2013; Hope et
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