What was once a German military defence line (Festungsfront Oder-Warthe-Bogen) between the Oder and Warta rivers is now one of Europe's biggest bat refuges. The new census has totaled 38,910 bats in the underground forts and tunnels - nearly 3 thousand more than last year and the highest number since the census was first held in 1999 by researchers from the University of Environmental and Life Sciences in Wrocław.
MRU is the biggest wintering site for bats in Poland, as well as one of the biggest in Europe. The census, always held on the second Sunday in January, brought together 70 chiropterologists from 12 countries. Nine species of bats were identified, Tomasz Kokurewicz from the University told Polish Press Agency PAP. He also said that the increased numbers of bats wintering here were a result of global warming: "There are more myotis myotis (greater mouse-eared bat) which prefers warmer habitats and winter temperatures between 7 and 9 Celsius. Because of warmer weather, this is now the temperature underground. It used to be much colder. That is why we are seeing more of these bats" he said.
The MRU area, he said, is a good environment for bats: "Those species that winter in the fortifications mostly live in woodland and near water, and there is plenty of that here".
The majority of the bats which winter in the fortifications are greater mouse-eared bats, Daubenton's bats and Natterer's bats, and there are also some rarer species such as Bechstein's bats and pond bats.
Poland is under obligation to report every five years to the European Commission on the condition of valuable habitats and protected species of animals living on Natura 2000 areas, to which MRU also belongs. A large part of the complex has the status of nature reserve.
The underground installations of the MRU fortification complex, which dates to the 1930s, include corridors, tunnels and chambers of a total length of 32 kilometres.
Source: PAP