The aim of this study was to examine the role of a high-elevation ice cave (Lodowa Cave in Ciemniak, Mt. Ciemniak, 1715 m a.s.l., Tatra Mountains, Poland) in the seasonal and nightly activity of bats. Bat activity was monitored using mist-netting and direct observations during the summer and autumn seasons of 2008–2011 and 2021. A total of 723 bats representing 10 of the 28 species known from Poland were captured. Eptesicus nilssonii predominated (57.5% of the total) and exhibited consistently high activity throughout the study period. Males predominated in almost all species, with E. nilssonii showing a strong male bias (85%), while adults were dominant and juveniles were rare (only 1.2% in E. nilssonii). Species composition and abundance varied seasonally, and swarming activity occurred between June and November, with a clear peak in July and August. Activity patterns were species-specific: E. nilssonii showed a pronounced peak approximately two hours after sunset, while M. mystacinus and P. auritus displayed distinct temporal activity profiles. A copulating pair of E. nilssonii was recorded in September 2011. Our findings suggest that high-altitude ice caves serve as key summer and autumn swarming and mating sites for E. nilssonii, highlighting their ecological importance in a warming climate.
Piksa et al. (2026) studied this question.