Abstract: Caves in Bulgaria have been studied primarily for their bat fauna, and the occurrence of other mammals in subterranean environments has remained largely unsynthesised. Here we compile and analyse records of non-volant mammals obtained during cave surveys and bat-monitoring activities conducted between 1993 and 2026. The dataset comprises 214 records of 14 taxa from 29 caves, based on direct observations, pitfall trapping, camera trapping, tracks and scats. Most records originate from the entrance and twilight zones, whereas deeper cave sectors were only rarely used. The assemblage is dominated by facultative cave visitors: two species Glis glis (Linnaeus, 1766) and Martes foina (Erxleben, 1777), both of which were classified as common, while most taxa were rare or accidental. Visiting caves for shelters and roosting by Rupicapra rupicapra balcanica (Bolkay, 1925) is a rarely documented phenomenon. Data from camera traps in a small cave in the Rhodope Mountains indicate that different chamois individuals frequently visit underground cavities, using them as shelter and resting sites. Pitfall data indicate strong seasonality in small-mammal detections, with captures concentrated in the warmer months and very limited winter representation, whereas winter surveys more frequently revealed the presence of medium and large mammals. Several records, including direct observations and feeding evidence, indicate opportunistic predation on bats by carnivores. These results show that the contemporary diversity of non-chiropteran mammals using Bulgarian caves has been underestimated. The concentration of records in ecotonal cave zones indicates consistent spatial overlap with bat roosts, highlighting the need to consider the broader mammalian assemblage in cave conservation and assessments of zoonotic risk in subterranean ecosystems.
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Supplementary materials [1]
01
Document title: An Excel dataset compiling all recorded occurrences of non-volant mammals included in this study, encompassing 214 records of 17 taxa from 29 caves in Bulgaria (1993-2026), with associated metadata on locality, detection method, and cave zone.
Kind of document: Microsoft Excel (OpenXML)
MIME type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
Document name: 000626000482026-01.xlsx https://doi.org/10.48027/hnb.48.071/01
Additional information
Received: 26 March 2026 · Accepted: 29 May 2026
Editor: Kal Ivanov
Conflicts of interest:
No potential conflict of interest has been reported by the authors, reviewers, or subject editor. As members of the editorial board, Mario Langourov, Ilya Acosta-Pankov and Nikolay Simov withdrew from discussions and decisions on the manuscript.
Authors’ contributions (using CrediT ↗):
Nia Toshkova: conceptualisation, data curation, formal analysis, investigation, methodology, software, visualisation, writing—original draft, writing—review and editing; Vladimir R. Todorov: data curation, formal analysis, investigation, methodology, software, visualisation, writing—original draft, writing—review and editing; Stanimira Deleva: data curation, formal analysis, investigation, methodology, software, visualisation, writing—original draft, writing—review and editing; Ilya Acosta-Pankov: data curation, formal analysis, investigation, methodology, validation, writing—original draft, writing—review and editing; Rostislav Bekchiev: investigation, methodology, writing—review and editing; Mario Langourov: investigation, methodology, visualisation, writing—review and editing; Nikolay Simov: conceptualisation, data curation, funding acquisition, investigation, methodology, project administration, resources, supervision, validation, ; Venislava Spasova: funding acquisition, project administration, writing—review and editing; Nedko Nedyalkov: data curation, investigation, methodology, supervision, validation, writing—review and editing.
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Cite as
Toshkova N., Todorov V. R., Deleva S., Acosta-Pankov I., Bekchiev R., Langourov M., Simov N., Spasova V., Nedyalkov N. 2026 Beyond bats: hidden mammalian biodiversity in Bulgarian caves. Historia naturalis bulgarica 48: 165–177.