Small mammals’ experts observed two of the extremely rare Northern Birch Mouse (Sicista betulina) near the village Neureichenau; an adult animal and a pup. Both male mice were only 6.5 to 5 centimeters. Their tails are twice longer than their body and play an important role for climbing. Another clear distinct feature is their black eel back.
Since the first verification of this species in Bavaria in 1950, the Northern Birch Mouse was observed only three times in the area of Freyung-Grafenau (at last 1994) and three times in the region of Oberallgäu (at last 2000). Other verifications in Germany are only known from Schleswig-Holstein.
Nowadays the Northern Birch Mouse is an indicator species of the North European and Asian forests and steppes. The distribution area extended from the south Finland, the Baltic States, the east of Poland and Belarus to the Ural and Caucasus. The last rediscovery in Bavarian Forest is typographically at the west brink of the main range of the species.
In the Red List of endangered animals in Bavaria the Northern Birch Mouse is classified in category G. That means the status is unknown, but a hazard is probable.