Réserve naturelle régionale de la grotte de la Baume: Mapped Protected Cave Landscapes

The Grotte de la Baume was first placed under formal protection in 1988 as a Réserve Naturelle Volontaire, a voluntary nature reserve designation in France. This status was intended to protect the cave and its bat populations, but the legal framework for voluntary reserves was abolished by the 2002 law on proximity democracy, and the designation lapsed in 2006.

Three bat-important sites in Franche-Comté, including the Baume cave, lost their protected status as a result. To prevent a gap in conservation, a prefectural biotope protection order was introduced to maintain protection of the Grotte de la Baume and the nearby Grotte de la Baume Noire at Fretigney-et-Velloreille. CPEPESC Franche-Comté then worked with the former Franche-Comté region to study the feasibility of a regional network of nature reserves dedicated to bats and their habitats.

This work led to the formal classification of seven regional nature reserves in 2015 and 2017, including the Grotte de la Baume RNR. The reserve was officially created by a regional council deliberation on 24 September 2015, with CPEPESC Franche-Comté designated as the managing body. A unified management plan covering the entire cave-and-bat reserve network was approved unanimously by the Bourgogne-Franche-Comté regional council on 27 September 2019, providing the first formalized framework for conserving the network's six priority bat species.

The reserve sits within a karst landscape typical of the limestone plateaus of the Haute-Saône. The plateau edge is marked by a clear rupture in slope, where the terrain drops into a rocky cliff face. This cliff line forms the opening into the cave system and contrasts sharply with the flatter agricultural plateau above.

The cave itself is the dominant topographic feature within the protected perimeter. Composed of Bajocien-age limestone, it extends several hundred meters into the rock through a series of interconnected chambers and galleries. The surface expression of the reserve is small, focused on the cliff base and the immediate surroundings of the cave entrances, reflecting the narrow but intensive conservation focus of the site.

The broader landscape context includes the corniche des Breuleux, an escarpment zone that itself carries ecological recognition as a ZNIEFF type I inventory area. This landscape of cliff, plateau, and valley edge gives the site its geological character and frames the underground world that the reserve is designed to protect.

The natural environment of the reserve is defined above all by its underground habitat. The cave provides the stable, sheltered conditions required by cave-dwelling bat species across the seasons, including specific humidity and temperature conditions that make it suitable for hibernation and for temporary occupation during transit periods.

Above ground, the reserve includes the rocky cliff face and the edge of the surrounding limestone plateau, which contribute to the broader ecological network around the cave. The escarpment supports habitats associated with cliff and rocky-slope ecosystems, while the surrounding landscape provides foraging habitat for bats emerging from the cave.

Within the wider conservation framework, the protection of associated forest habitats is also recognized as important. These above-ground habitats may be addressed through the broader network's management planning, since they support bat foraging and movement corridors beyond the cave itself.

Bats are the single most important group of animals associated with the reserve, and the reason the site exists. Monitoring at the Grotte de la Baume has identified 13 species or species groups using the cave across the year. The cave plays distinct roles in different seasons for different species.

During the autumn transit period, several hundred Schreibers' long-fingered bats use the cave as a temporary roost. In winter, the cave functions as a hibernation site of regional importance, with populations of greater horseshoe bats reaching around one hundred individuals and lesser horseshoe bats averaging around fifteen individuals. The cave sits within a network of underground sites used by these species as they shift between roosts through the annual cycle.

The reserve's management plan addresses six priority bat species in particular: Schreibers' long-fingered bat, lesser mouse-eared bat, Mediterranean horseshoe bat, greater horseshoe bat, lesser horseshoe bat, and Geoffroy's bat. Many of these species are sensitive to disturbance, particularly during hibernation and maternity periods, which is why human access to the cave is restricted year-round.

The reserve's conservation significance is strongly focused on the protection of an underground habitat used by sensitive bat populations. Its small surface area reflects a targeted strategy: protecting the cave and the immediate surrounding rock environment in order to maintain the conditions bats require for hibernation, transit, and reproduction.

The reserve benefits from multiple layers of protection that reinforce its conservation role. These include a ZNIEFF type I inventory zone covering the corniche and cave area since 2009, a Natura 2000 special conservation site protecting a network of horseshoe bat caves in the Vesoul region since 2015, and a prefectural biotope protection order for the cave dating from 2007. Together with the regional nature reserve classification from 2015, these tools form a robust protection framework.

The most important conservation concern addressed by the reserve is the fragility of underground environments to human disturbance. Even small changes in conditions inside the cave can cause bat mortality or force colonies to relocate to less suitable sites. The reserve's regulatory framework, including year-round public access restrictions, is designed to prevent such disturbance and to preserve the cave's ecological functionality within the wider bat conservation network.

The reserve's strongest distinguishing features include its role within a regional network of bat-focused cave reserves and its layered protection framework, including ZNIEFF, Natura 2000, and biotope protection status. Its very small size is itself a defining trait, reflecting a conservation approach centered on safeguarding a single underground feature rather than a broad landscape.

The site's educational and scientific value lies in its long-term bat monitoring record and its contribution to understanding how cave networks function together across seasons. The reserve also represents a successful collaborative conservation effort between the CPEPESC Franche-Comté commission and regional authorities to rebuild protection for sites that lost their status in the 2000s.

The Grotte de la Baume is not a publicly accessible site; the cave is closed to visitors year-round in order to protect sensitive bat populations. As a result, there is no traditional visitation season associated with the reserve.