The bat ringing method makes a significant contribution to research into the migratory behaviour of bats. For example, ringing has revealed that greater mouse-eared bats(Myotis myotis) fly over 100 kilometres to their wintering grounds. Other species such as the hoary bat(Pipistrellus nathusii), the common noctule(Nyctalus leisleri) and the common noctule(Nyctalus noctula) even fly 1,000 to 2,000 kilometres between their summer and winter habitats. Of course, the small mammals also cross national borders. Rough-skinned bats ringed in the north-east German lowlands in summer were reported from the Netherlands, central and south-west Germany, Switzerland, Italy and southern France.
The cross-border flight activity of bats also requires cross-border protection of the animals. For this reason, the "Agreement on the Conservation of European Bat Populations" (UNEP/EUROBATS) was signed in 1991, to which 26 European countries now belong. In Germany, all bat species are protected by the Federal Nature Conservation Act.
In the 70-year history of bat ringing, around 350,000 bats have been individually marked in Germany and neighbouring countries (e.g. the Netherlands, Poland and Austria). The recovery rate by the ringers themselves is very high due to the bats' roosting fidelity and can be over 25 per cent. In contrast, only around 1 per cent of recoveries are genuine long-distance recoveries at a greater distance from the ringing site.