The olm – proteus anguinus – is a real cave dweller. The animal belonging to the species of the caudates has its natural range exclusively in the Dinaric Mountains in the southwestern Balkans, in today’s Slovenia. In the wild, olms live there in the underground flowing waters of the Karst rock.
But how does the olm get into the Olms Lake in the Hermanns Cave of Rübeland?
Not naturally; the first five animals were brought into the Hermanns Cave in Rübeland by humans in 1932. For this purpose, the Olms Lake was artificially created.
After World War II ended, it remained uncertain how many of the five animals were still alive. Legend says that American foot soldiers roasted at least one animal and ate it as a dare. Unfortunately, in 1954 only two olms could be counted.
At the end of 1956, a couple from Rübeland brought 13 olms with them from a field excursion from Postojana (Adelsberg / Slovenia). 11 of these animals arrived safely in Rübeland and were also released in the Olms Lake in January 1957.
The olm has a shape similar to an eel. The body is about 25-30 cm long and has a slightly flattened tail. The legs are very fine-boned and have three toes on the front and two on the hind legs. The pigmentless skin of the olm seems whitish to flesh-colored. The head is wider than the longish body and looks like a cropped snout. The eyes of the older animals are no longer visible because they are covered with skin. On the neck there are blood-red gills. The olms also have functional lungs.
Little is known about the olm as it mainly lives in the dark. However, it has been found that the animal can go without food for up to 12 years, the olm in the caves of Rübeland also has no natural predators; that is why it can live well over 70 years.
Microorganisms such as crustaceans are main part of its nutriment.
The breeding of the olm is very complicated. Unfortunately, no natural reproduction of the animals has yet been observed in Rübeland.
By 2015 only 9 of the 20 olms were still living in Rübeland. In addition to that the gender of the animals was completely unknown to date. The only presumption was that all animals were male. This conclusion was drawn from the fact that no mating / reproduction was observed and no eggs could be found.
Therefore, the tourism company of the city of Oberharz am Brocken, as the operator of the caves in Rübeland, initiated a project to save the olms of theHermanns Cave. The focus here was on the observation and documentation of the animals in their habitat in Rübeland.
As part of the intensive care of the olms, the employees of the Hermanns Cave found 5 eggs of olms for the first time in February 2016. These have been relocated to specially prepared aquariums, where they should develop undisturbed by the adult olms and far away from visitors. Despite the small number of eggs, there was still great hope that after 85 years there could be offspring of the olms in Rübeland.
That is why the disappointment was even greater when the eggs did not develop into offspring. But: after all, the project was able to prove for the first time that these olms lay eggs. Therefore, there is still hope that there might be offspring in the future.
Further olm projects
Since unfortunately two of the nine olms died in 2016, another project “The olms of the Hermanns Cave in Rübeland – save a threatened existence of an FFH species” was initiated in mid-2017.
In addition to checking the keeping conditions the state of health was also examined. Using an ultrasound device, experts from the Leibniz Institute for Zoo and Wildlife Research were able to confirm that the remaining olms are divided into three male and four female olms in the Hermanns Cave.
Research projects on the olms in Rübeland will be continued and initiated in 2020 and in the future in order to protect this unique and rare species in the dripstone caves of Rübeland.