Photo credit: (c) Simion MECHNO / AGERPRES ARCHIVE

The Bat Cave scientific reserve includes the cave itself, as well as some six hectares of land surrounding it and overlapping a part of the Rarau — Pietrele Doamnei protected area. The reserve is included in Europe’s Natura 2000 network of protected areas.

The cave has a height difference of 86 meters and its galleries have a total length of 340 metres; the entry into the sinkhole is through a shaft some 14 meters deep. “Since this is a less friendly cave, the descent into the galleries requires speleological knowledge and specific equipment,” says speleologist Adrian Done.

He explains that this is the hibernation place for the largest population of bats in eastern Romania, specifically some 2,500 individuals from 4-5 species. In summer, during the peak mating season, there is a surge in the number of species present here that can go as high as 15 of the 31 living in Romania and 45 in Europe.

The species that inhabit the Rarau area include the whiskered bat, Brandt’s bat, Bechstein’s bat, the greater mouse-eared bat, the lesser mouse-eared bat, the brown long-eared bat or the lesser horseshoe bat. Yet the predominant species in the Bat Cave are the greater mouse-eared bat (Myotis myotis) and the lesser mouse-eared bat (Myotis blythii).

The bats are compactly clustered in colonies, all facing the same direction and crammed so tightly that they form a sort of fur-and-skin rug hanging from the ceiling of the cave. The number of individuals in a colony varies from small groups of 3-12 to over 1,000. Colonies can settle one meter above the floor, but also in the highest points of the cave halls.

Most colonies are formed in the bat hall, with their number growing from 40 in February to 55 in October. The number of colonies and individuals, respectively, decreases as one advances deeper to the ther halls.

The observations made in December 1962 by researcher Niculae Valenciuc from the “Alexandru Ioan Cuza” University of Iasi showed that the bats return to the winter roost beginning with August. Most of the chiropterans (70 — 80 percent) return in October, when the effort of adjusting to the new conditions is minimal, given that the air temperature is practically equal inside and outside and the relative humidity of the air outside is much closer to the one inside the cave, and the bats must lower their body temperature to 4-5 degrees Celsius during hibernation.

The Bat Cave differs from other caves in the country through the absence of stalactites, stalagmites or any other calcite depositions. Unlike the caves created by the flow of water, the Bat Cave in Rarau was formed by the splitting of the stone block that slipped on the less rigid underlying layer, due to lateral gravitational traction.

The ramiform cave has six halls — the Hidden Hall, the Branched Hall, the Rectangular Hall, the Bats Hall, the Lighted Hall and the Tapered Hall — connected between them through shafts almost 14 meters deep. The cave was investigated in 1954 by a team of climbers from the Central Army House, and in 1975 the “Emil Racovita” Speleology Group in Bucharest charted the cave for the first time and designed its first map.

The Bat Cave is entered in the Systematic Catalog of Romanian Caves. The first research on the cave fauna was conducted in 1962, in an attempt to answer the question ‘Where do the bats head for from the places where they live in colonies during the warm season?’ The total population was assessed in those years at more than five thousand individuals.

As Adrian Done explains, the decrease in the bat population is determined by natural selection, as a female bat has just one baby a year and two just in exceptional situations. As an interesting detail, Done said the bats have ‘birth centers’, where males are not allowed. One such center is currently in Suceava, where some two to three hundred individuals gather during the gestation period.

The bat population in the Rarau cave has been monitored every winter since 2002. The finding was that it has been relatively constant, at around 2,000 — 2,500 individuals.

Underground sites, such as caves, are important habitats for bats worldwide. In northern Europe, such shelters are mainly used by chiropterans for hibernation.

In the European Union, the bats and their reproduction and resting roosts are protected.

Speleologist Adrian Done mentions that the Rarau Bat Cave is a sinkhole of no tourist interest, as it has no spectacular formations, while its fragmentation can cause all sorts of unpleasant surprises to insufficiently prepared tourists.

As the speleologist emphasized, bats feed exclusively on insects (estimates from studies show that some bats eat more than 70 percent of their weight in insects each night) and are important for keeping the balance of the ecosystem, protecting forests, agriculture and people. AGERPRES