Twenty bat species recorded in Georgia’s caves
Twenty of the 30 bat species known from Georgia have been found in caves and other underground sites. Yet only about 15% of those sites have been surveyed for bats.
Researchers from the Institute of Zoology at Ilia State University and EUROBATS brought together the known data on bats in Georgia’s underground sites: records published since 1912 and more than 300 surveys carried out in 1999–2024. In total, they gathered 331 records from 115 underground sites. Twenty of the 30 bat species known from the country were found in caves, mines and man-made caves. The paper was published in Subterranean Biology on 22 November 2024.
What did the study find?
Papers published in 1912–2010 listed 13 bat species from 71 underground sites in Georgia. The authors added 44 new sites. Today there are 331 records from 115 sites, covering 20 bat species in three families and ten genera. One of them, Blasius’s horseshoe bat, turned out to be new to the country. Six species are ones that do not usually use underground sites.
The researchers checked caves in every season from 1999 to 2024. During the swarming period they also set mist nets at cave entrances. Captured bats were measured to identify the species and released on the spot. For the older records, the authors visited libraries and museums in Georgia and Russia, because most of those papers were written in Georgian and Russian.
The picture is still incomplete. Georgia has about 2,000 underground sites, and only about 15% of them have been surveyed for bats. Karst covers 6.4% of the country, mostly in western Georgia, with more than 1,500 known karst and conglomerate caves. In the east, the researchers also checked man-made caves, mainly in the gorges of the Mtkvari, Iori, Khrami, Algeti and Mashavera rivers.
Which bats turn up most often?
The greater horseshoe bat (Rhinolophus ferrumequinum) has the most records, 67. The lesser horseshoe bat (Rhinolophus hipposideros) follows with 65. Next come the common bent-winged bat (Miniopterus schreibersii, 42), the lesser mouse-eared bat (Myotis blythii, 40) and the Mediterranean horseshoe bat (Rhinolophus euryale, 36). All five mainly live in caves.
Most of these species live in cave colonies of up to 1,000 individuals. The greater horseshoe bat, the lesser mouse-eared bat and the common bent-winged bat appear both in records from before 1999 and in the new surveys. Species richness is highest at 0–300 m and 1,200–1,500 m above sea level, followed by 600–900 m.
A new species, and one that has gone unseen
Blasius’s horseshoe bat (Rhinolophus blasii) is the only one of the 20 species that roosts exclusively in caves. It was first recorded in Georgia in 2006 and has since been found in three more caves.
Mehely’s horseshoe bat (Rhinolophus mehelyi) was last recorded in Georgia in 1964. In 25 years of surveys, the researchers did not find it once. They still do not rule out that the species survives in the country, and they call for continued monitoring.
Of the 20 species, three are on the Georgian Red List and one is on the IUCN Red List. The Mediterranean horseshoe bat is Vulnerable (VU) on the Georgian Red List, and the common bent-winged bat is assessed as Vulnerable (VU) on the IUCN Red List. All five of the most common species are Emerald Network priority species.
Where are the largest colonies?
Ghliana Cave holds one of the country’s largest nursery colonies, where bats raise their young. The lesser mouse-eared bat and the common bent-winged bat live there every year. In some years and seasons, greater and Mediterranean horseshoe bats join them, and sometimes Myotis emarginatus too. The colony varies from 4,000 to 8,000 individuals from year to year and peaks from late July to early August.
In some years, 8,000 or more bats gather in Samertskhle Klde Cave, mainly lesser mouse-eared bats and common bent-winged bats. The largest known winter colony is in Sakishore Cave, where more than 1,000 common bent-winged bats hibernate.
What threatens cave bats?
The authors scored seven caves with colonies for three threats: human disturbance, destruction or change of use of the habitat, and light pollution. They also took into account how easy each cave is to reach. Ghliana Cave came out as the most threatened, with 2.75 on a three-point scale. This is despite the Ministry of Environmental Protection and Agriculture drawing up a conservation action plan for Ghliana in 2019. The other caves face moderate threat from human disturbance.
Only 18 caves or cave complexes are legally protected, including the Imereti Caves Protected Area. Among the protected caves, only Ghliana and Melouri host large colonies. The authors call for protected status for four more caves: Samertskhle Klde, Vardigora, Becho and Sakishore. They say this would improve the conservation status of the Mediterranean horseshoe bat, the lesser mouse-eared bat and the common bent-winged bat.
The authors name Imereti, Samegrelo and Abkhazia as the most important regions for bat conservation. Many caves there are hard to reach, which gives bats some protection, but not enough. The land around the caves, where bats feed and travel at night, also needs protection. If you find a bat colony in a cave, do not disturb it or shine a torch at it.
What remains unclear?
The study dates from 2024. Any data published since then are not in this article.
About 85% of underground sites have not been surveyed for bats, so species distributions and colony numbers are not fully known. Colony sizes are rough estimates: the authors counted large groups in parts or from photographs.
Species distribution maps are published on a 50 × 50 km grid so that the exact sites of threatened bats are not revealed. There are no bat profiles in this atlas yet. If a bat flies into your home, see our guide. For other mammals, see the mammals page.
