Bats in the Sontheim Cave
The first report on animals in the „Erdloch bey Sontheim“, by Rössler in 1791, states: „Living things, e.g. bats, etc., are never found in the cave“. Nevertheless, it can be assumed that bats used the Sontheim cave as a roost in former times, because bat bones were found in a breccia in the entrance area of the Sontheim cave on the occasion of an inspection during the conference of the Main Association of German Speleologists in Laichingen in 1926 (HELLER 1928), the age of which, however, cannot be stated exactly. The bat species described there are: The fringed bat, the Bechstein’s bat, the water bat and the brown long-eared bat.
The occurrence of the water bat is special, because this species used to be found extremely rarely in the Swabian Alb. Otherwise, the species mentioned still occur in the Sontheim Cave.
The next reference to bats comes from Dr. HANS LÖHRL, who visited the Sontheim Cave in the winter of 1938/39 and discovered and also photographed a large hibernation group of the pug bat. Such a large gathering of pug bats was also something special at that time and unique for the region of the Swabian Alb.
Fig. 16: Hibernation group of the pug bat in the Sontheim cave in the winter of 1938/39.
The bats spend the winter period, which is poor in food, in hibernation, during which the animals cool down to 0° C. This reduces their energy and food supply. This greatly reduces their energy and food consumption and they can survive the winter with the fat reserves they have accumulated in autumn alone.
Fig. 17: Ceiling in the so-called pug hall.
The large number of bats and especially the rare pug bat led early on to the first protective measure for hibernating bats in the Swabian Jura. In 1959, the first bat gate was installed there, which became the model for many other such protective measures throughout Germany.
Fig. 20: First bat gate in Sontheim Cave shortly after installation. ROLF GRIESINGER is on the left, HANS RUOPP on the right.
From 1969 onwards, systematic counts of the bat population take place. While up to 1,000 bats were found until the end of the sixties, there were just 17 animals in the winter of 1976/77. Since then, the population of hibernating bats has recovered.
Fig. 21: Population development of hibernating bats from winter 1951/52 until today. The figures before 1969 were compiled from ringing and recovery data as well as other information.
From the beginning of August, the Sontheim Cave is also populated by bats in summer, although they cannot be seen during the day. They are probably hiding deep in crevices. Individual nocturnal flight observations indicate that up to 500 bats of all species also found in winter fly around there at the same time. This behaviour is generally referred to as swarming, and its significance is not yet fully understood. The bats of all species meet in their future winter quarters. They are probably checking whether it is still suitable. However, swarming also has a social component, as courtship and, later in the year, mating take place.
Fig. 23: The water bat used to be extremely rare in the Swabian Alb. Today it regularly occurs in the Sontheim Cave. 31
Sontheim Cave is now one of the most important winter roosts for bats in Baden-Württemberg, which is why it is closed to visitors from the beginning of November to the end of April. This protective measure is absolutely necessary as many of the native bats are threatened in their population, some species, e.g. the pug bat and the lesser horseshoe bat are already extinct in our country. In the mid-1970s, there were only a few specimens of the greater mouse-eared bat left.
Fig. 27: At times, only individual specimens of the Greater Mouse-eared Bat could be observed in the Sontheim Cave. Today there are again whole clumps of bats hanging from the ceiling.
Dr. Alfred Nagel (abridged)
Further information in the brochure on Sontheim Cave, available at the cave ticket office.