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Recovery of bat hibernation colonies in Devetashka Cave!

Recovery of bat hibernation colonies in Devetashka Cave!

29.11.2012
All hibernation colonies and clusters were located in their traditional winter spots. Every colony was precisely photographed with a digital camera. Number of individuals was precisely scored by a surface area estimate considering the packing densities of each species observed in the cave. The largest colony, which covered an area of about 60 square meters was estimated to hold about 21 995 individuals. The total number of all bats was estimated to 30 880 individuals belonging to 4 species.
This number is close to the numbers counted during the winters before the start of the filming of “The Expendables 2”. Furthermore, it exceeds three times the numbers reported right after the filming of the Hollywood production.

This practically confirms the assumption that disturbance caused by filming of the “The Expendables 2” was the major reason for the decline of bats, which was reported right after the filming.
The monitoring confirmed that in case of no significant disturbance, the cave typically hosts over 30 000 bats. At the same time the observations rejected the claims of MoEW that the low number of bats is due to the warm winter conditions and not the filming.

A summary of the overall number of hibernating bats in Devetashka Cave for the past three winters shows the following:
23.01.2011 - 33 770 individuals (the winter of 2011 - a year before the start of the filming)
10.12.2011 - 10 400 individuals (a count right after the filming)
14.02.2012 - 10 665 individuals (a count in mid-winter, 2 months following the filming)
23.11.2012 - 30 880 individuals of four species as follows:

Schreiber's Bat (Miniopterus schreibersii) - 30 420 individuals
Greater Horseshoe Bat (Rhinolophus ferrumequinum) - 160 individuals
Common Noctule (Nyctalus noctula) - > 300 individuals (probably much more yet hidden in deep crevices)
Long-fingered Bat (Myotis capaccinii) - about 50 individuals but probably much more yet hidden in deep crevices)


The high numbers reported are resulting from the low levels of disturbance in the inner parts of the cave, thus securing normal conditions for the natural hibernation of the bats.

The assessment showed that the temporary fence symbolically limiting the access to the dark parts of the water gallery of the cave is half-destroyed. The information signboard istalled by the Municipality of Lovech last summer has also gone missing. The team partially repaired the wall with materials at hand.
Urgent measures are however needed to guarantee no visitor access to the sites used by the bats and thus prevent their disturbance.
At present there is no control over the access and any visitor is free to enter the inner parts of the cave and disturb the bats. The function of the wards is limited to writing down the registration plates of all vehicles, which are parking nearby. In wintertime the cave is visited significantly less frequent than during summertime, when we have seen a daily flow of some 600-800 people (weekends) and about 200-400 tourists during the week.

The high numbers of bats observed in the cave indicate that the site has recovered its status as one of the most important underground bat roost in Bulgaria and Europe. This status will be certainly jeopardized unless the new order for protecting the cave is urgently enforced.

After a series of meetings and consultations, the text and regimes set with the order have already been coordinated with all concerned parties, yet the order has not been enforced by MoEW. This fact, as well as the lack of a Management Plan for this protected area prevents the Municipality of Lovech to manage the cave following regulations and conditions which would guarantee its effective and constant protection as a remarkable natural phenomena and a habitat of rare and threatened species of bats and endemic cave-dwelling invertebrates.

For further information, please contact:
Boyan Petrov - Bat Research & Conservation Centre – National Museum of Natural History/ BAS phone: + 359 893322107