With only three known occurrences (in Schleswig-Holstein, Bavarian Forest and Bavarian Alps), the Northern Birch Mouse (Sicista betulina) is one of the most endangered mammal species in Germany. This species was detected by using camera traps in several areas along the Green Belt – in 2020 for the first time also verified on LIFE project areas of BUND Bayern in Haidmühle (Langreut) and Philippsreut (Wagenwasser). The photo traps are part of a joint research project run by the Bavarian regional association for bird protection (LBV) and BUND Bavaria as part of the Bavarian Biodiversity Programme 2030 “NaturVielfaltBayern”.
The mouse with the characteristic dorsal strip on its back is a tiny creature with a head and torso length of 50 to 75 millimeters and a weight of between 5.5 and 13.5 grams – but is far superior to the larger mouse species in wet areas. Instead of running through the wet, it climbs perennials and bushes. This perfect adaptation to life in a mire makes it a “flag ship species”. However, this adaptation can also be its downfall if it does not succeed in securing, enlarging and interlinking the existing mires and wetland habitats in the long term.
From nature conservation point of view, the discovery of this rare species is a stroke of luck. Nevertheless, at the same time it is a big challenge, as the implementing of all the planned renaturation measures in the project areas is now to be revised and adjusted. This is because construction measures, such as the planned dismantling of drainage ditches in the “Langreut” area, pose a threat to the mouse, even if the species benefits in the long term from the rewetting of the areas. Compensatory habitats must therefore be created to which the mice can “move” as long as the construction measures are carried out. In addition, implementation must be adapted to the life rhythm of the mouse (hibernation, rearing of young, etc.). To this end, BUND Bayern continues to work closely with the expert David Stille. The long-term goal is to increase the habitat of the Northern Birch Mouse and to link previously isolated sub-populations along the Green Belt.